Pages 182-192 and Manufacturing Engineering
Formation of gradient surface layers on high speed steel by laser surface alloying process
M. Bonek*
Division of Materials Processing Technology, Management and Computer Techniques in Materials Science, Institute of Engineering Materials and Biomaterials, Silesian University of Technology,
ul. Konarskiego 18a, 44-100 Gliwice, Poland
* Corresponding e-mail address: miroslaw.bonek@polsl.pl
Received 29.10.2012; published in revised form 01.12.2012
ABSTRACT
Purpose: The purpose of this research paper is focused on the high speed steel HS6-5-3-8 surface layers improvement properties using HPDL laser. The paper present laser surface technologies, investigation of structure and properties of the high speed steel alloying with the WC, VC, TiC, SiC, Si3N4 and Al2O3 particles using high power diode laser HPDL.
Design/methodology/approach: Investigation indicate the influence of the alloying elements on the structure and properties of the surface layer of investigated steel depending on the kind of alloying carbides, oxides, nitrides and power implemented laser (HPDL).
Findings: Laser alloying of surface layer of investigated steel without introducing alloying additions into liquid molten metal pool, in the whole range of used laser power, causes size reduction of dendritic microstructure with the direction of crystallization consistent with the direction of heat carrying away from the zone of impact of laser beam. In the effect of laser alloying with powder of the WC, VC, TiC, SiC, Si3N4 and Al2O3 particles occurs size reduction of microstructure as well as dispersion hardening through fused in but partially dissolved particles and consolidation through enrichment of surface layer in alloying additions coming from dissolving elements. Introduced particles of carbides, oxides, nitrides and in part remain undissolved, creating conglomerates being a result of fusion of undissolved powder grains into molten metal base. In effect of convection movements of material in the liquid state, conglomerates of carbides arrange themselves in the characteristic of swirl.
Practical implications: Laser surface modification has the important cognitive significance and gives grounds to the practical employment of these technologies for forming the surfaces of new tools and regeneration of the used ones.
Originality/value: The structural mechanism was determined of surface layers development, effect was studied of alloying parameters, gas protection method, and method of applied onto the steel surface on structure refinement and influence of these factors on the mechanical properties of surface layer, and especially on its hardness and microhardness.
Keywords: Heat Treatment, Laser, Tool Materials, Hardness
Reference to this paper should be given in the following way:
M. Bonek, Formation of gradient surface layers on high speed steel by laser surface alloying process, Archives of Materials Science and Engineering 58/2 (2012) 182-192.
MATERIALS MANUFACTURING AND PROCESSING
1. Introduction
The basic and most often applied materials for manufacturing hot-work tools and also metal forms used in casting are alloyed hot-work steel. The properties of a surface layer of those steel must protect against the loss of exploitation durability and in particular must be characterised by wear resistance at the higher temperature, load and corrosion resistance of processed material. High speed steels belongs to the group of martensitic steel used in the production of forging tools. The microstructure of high speed steels changes several times during the complex thermo-plastic treatment. The aim of this processing is to obtain high wear and thermal fatigue resistance. Carbides release of two kinds is responsible for high mechanical properties. The primary release - produced in the process of crystallisation and the secondary release - a result of the thermoplastic treatment. The examination of the possibilities of the increase of application properties of tool steels having martensitic matrix by the change of chemical composition in the conventional way is very limited. It may be expected that the wear resistance as well as hardness and chemical stability will be increased in the materials in which additional, more stable and hard molecules were introduced to the native material. The future direction of research into the improvement of materials properties is a laser modification of the tool surface layer structure either by a laser relmelting or alloying by the use of materials such as tungsten carbides having huge hardness. The effect of the process in which the cooling speed is very high, is the minute-grained structured material with over-cooling phases [1-6].
The laser heat treatment includes operations which are conducted using the laser beam as the source of energy needed for heating the surface layer of the processed material, to change its structure for obtaining the relevant mechanical, physical, or chemical properties, improving service life of the processed element. Two methods of forming the surface layer have found applications so far within the framework of the laser heat treatment of the surface layer, namely:
x Forming by phase transformations in the solid state, consisting in heating of the surface layers to the austenitizing temperature and their sudden cooling - quenching, or slow cooling - annealing and tempering, or heating up, e.g., for improving the ductility before the succeeding surface treatment or shaping, like e.g., machining of the sintered carbides, welding, plastic working, laser treatment, e.g., before cladding or quenching (to avoid cracks or to assist the heating process).
x Forming by remelting the surface layer, consisting in heating the material above the solidus temperature, its rapid solidification, and in phase transformations in solid state.
Surface layers with the very refined structure or amorphous, with the unchanged chemical composition in respect to material’s core, but with significant chemical homogeneity, can be obtained with this laser forming method, depending on cooling rate. Variations of material forming by remelting its surface layer include: enrichment (alloying) of the surface layer with the selected alloying elements and cladding, consisting in applying a layer with another chemical composition onto the formed material, that ensures corrosion resistance, high-temperature resistance, or decorative properties [7-16].
during remelting, which results with a big temperature gradient between the liquid material layer and the matrix. Mixing of the molten metal occurs because of the convection motions during laser treatment with remelting. These motions originate because of the temperature difference between the remelted surface and the bottom of the remelted region, and moreover because of the protective gas blow-in and “pressure” of the laser beam. Quick solidification occurs after remelting and mixing the molten metal due to the big temperature gradient. The investigation results obtained may be used for the further research on optimisation of the surface layer properties of the high speed steels, targeted at obtaining tools with the possibly high mechanical and service properties. The goal of this work is studying the structural mechanisms and selected, for comparison, properties of the surface layers obtained by the high power diode laser (HPDL) treatment of the high speed steels.
The difficulty of that method results from two facts. First of all, it is hard to operate the concentrated source of heat and secondly, there is no theoretical data defining expected new structures created under those conditions. Empirical data, on which one usually is based, is not treated precisely as the only source of knowledge because the process is characterised by same deviation from the state of balance, resulting from high increase in temperature as well as great thermal gradients [4-8].
Diode lasers have been known for many years and used mainly in electronic devices and metrology. The dynamical development of materials engineering (progress in production of semi- conductors) allowed for the introduction of industrial HPDL lasers. Diode lasers produced nowadays achieve power up to 6 kW on the surface of the laser beam focusing. Diode lasers of ROFIN DL type are characterised by a rectangular or linear shape of beam focus having multi-mode energy distribution. In that type of a laser power density delivered to a surface layer of processed materials is smaller in a comparison with mono-mode distribution, characteristic of other types of lasers and energy is spread evenly on the surface of the laser beam focus. Thanks to that phenomenon a HPDL laser is suitable for the modification of a material surface layer. It is confirmed by an empirically proved high energy absorption coefficient for steels (20-40%), high efficiency and the possibility of the precious control of the amount of energy delivered to a material surface layer. The condition of the surface layer of the processed material and especially its roughness and absorption coefficient are the most important factors in the process of laser treatment of materials. When laser radiation, as any light beam, is spread in different medium, it follows certain rules of absorption, reflection and refraction. The absorbance coefficient, characteristic of every material, is not constant in the laser processing and risen markedly when the material heated is covered with the oxides layer and when the temperature is its melting one [17-26]. The application of adequate protective gases as well as the correct choice of the nozzle and its position guarantee the high quality of the bead face and the recurrence of the results obtained. The phenomenon of wear of the working surface of tools, to which laser modification of the surface layer is applied, due to friction features an important aspect of the contemporary surface engineering. The friction process between two surface leads to their wear and is connected with energy losses. It is disadvantageous especially when it occurs along with other factors
READING DIRECT: www.archivesmse.org 1831
1. Introduction
The basic and most often applied materials for manufacturing hot-work tools and also metal forms used in casting are alloyed hot-work steel. The properties of a surface layer of those steel must protect against the loss of exploitation durability and in particular must be characterised by wear resistance at the higher temperature, load and corrosion resistance of processed material. High speed steels belongs to the group of martensitic steel used in the production of forging tools. The microstructure of high speed steels changes several times during the complex thermo-plastic treatment. The aim of this processing is to obtain high wear and thermal fatigue resistance. Carbides release of two kinds is responsible for high mechanical properties. The primary release - produced in the process of crystallisation and the secondary release - a result of the thermoplastic treatment. The examination of the possibilities of the increase of application properties of tool steels having martensitic matrix by the change of chemical composition in the conventional way is very limited. It may be expected that the wear resistance as well as hardness and chemical stability will be increased in the materials in which additional, more stable and hard molecules were introduced to the native material. The future direction of research into the improvement of materials properties is a laser modification of the tool surface layer structure either by a laser relmelting or alloying by the use of materials such as tungsten carbides having huge hardness. The effect of the process in which the cooling speed is very high, is the minute-grained structured material with over-cooling phases [1-6].
The laser heat treatment includes operations which are conducted using the laser beam as the source of energy needed for heating the surface layer of the processed material, to change its structure for obtaining the relevant mechanical, physical, or chemical properties, improving service life of the processed element. Two methods of forming the surface layer have found applications so far within the framework of the laser heat treatment of the surface layer, namely:
x Forming by phase transformations in the solid state, consisting in heating of the surface layers to the austenitizing temperature and their sudden cooling - quenching, or slow cooling - annealing and tempering, or heating up, e.g., for improving the ductility before the succeeding surface treatment or shaping, like e.g., machining of the sintered carbides, welding, plastic working, laser treatment, e.g., before cladding or quenching (to avoid cracks or to assist the heating process).
x Forming by remelting the surface layer, consisting in heating the material above the solidus temperature, its rapid solidification, and in phase transformations in solid state.
Surface layers with the very refined structure or amorphous, with the unchanged chemical composition in respect to material’s core, but with significant chemical homogeneity, can be obtained with this laser forming method, depending on cooling rate. Variations of material forming by remelting its surface layer include: enrichment (alloying) of the surface layer with the selected alloying elements and cladding, consisting in applying a layer with another chemical composition onto the formed material, that ensures corrosion resistance, high-temperature resistance, or decorative properties [7-16].
Part of the absorbed heat energy penetrates inside the material during remelting, which results with a big temperature gradient between the liquid material layer and the matrix. Mixing of the molten metal occurs because of the convection motions during laser treatment with remelting. These motions originate because of the temperature difference between the remelted surface and the bottom of the remelted region, and moreover because of the protective gas blow-in and “pressure” of the laser beam. Quick solidification occurs after remelting and mixing the molten metal due to the big temperature gradient. The investigation results obtained may be used for the further research on optimisation of the surface layer properties of the high speed steels, targeted at obtaining tools with the possibly high mechanical and service properties. The goal of this work is studying the structural mechanisms and selected, for comparison, properties of the surface layers obtained by the high power diode laser (HPDL) treatment of the high speed steels.
The difficulty of that method results from two facts. First of all, it is hard to operate the concentrated source of heat and secondly, there is no theoretical data defining expected new structures created under those conditions. Empirical data, on which one usually is based, is not treated precisely as the only source of knowledge because the process is characterised by same deviation from the state of balance, resulting from high increase in temperature as well as great thermal gradients [4-8].
Diode lasers have been known for many years and used mainly in electronic devices and metrology. The dynamical development of materials engineering (progress in production of semi- conductors) allowed for the introduction of industrial HPDL lasers.
Diode lasers produced nowadays achieve power up to 6 kW on the surface of the laser beam focusing. Diode lasers of ROFIN DL type are characterised by a rectangular or linear shape of beam focus having multi-mode energy distribution. In that type of a laser power density delivered to a surface layer of processed materials is smaller in a comparison with mono-mode distribution, characteristic of other types of lasers and energy is spread evenly on the surface of the laser beam focus. Thanks to that phenomenon a HPDL laser is suitable for the modification of a material surface layer. It is confirmed by an empirically proved high energy absorption coefficient for steels (20-40%), high efficiency and the possibility of the precious control of the amount of energy delivered to a material surface layer. The condition of the surface layer of the processed material and especially its roughness and absorption coefficient are the most important factors in the process of laser treatment of materials. When laser radiation, as any light beam, is spread in different medium, it follows certain rules of absorption, reflection and refraction. The absorbance coefficient, characteristic of every material, is not constant in the laser processing and risen markedly when the material heated is covered with the oxides layer and when the temperature is its melting one [17-26]. The application of adequate protective gases as well as the correct choice of the nozzle and its position guarantee the high quality of the bead face and the recurrence of the results obtained.
The phenomenon of wear of the working surface of tools, to which laser modification of the surface layer is applied, due to friction features an important aspect of the contemporary surface engineering. The friction process between two surface leads to their wear and is connected with energy losses. It is disadvantageous especially when it occurs along with other factors
1. Introduction
deteriorating properties of the surface layer, like corrosion, erosion, mechanical and thermal fatigue [27-33].
The goal of the work is to determine the technical and technological conditions for alloying the surface layer of the high speed steel HS6-5-3-8 with the high power diode laser (HPDL), and of the relationship between the parameters of laser treatment and the properties of the surface layer which increase the exploitation durability of high speed steels.
2. Material for investigation
The experiments were made on specimens made from the high speed steel HS6-5-3-8. The chemical composition of the steel is presented in Table 1. The investigated steel was molten in the electric vacuum furnace at the pressure of about 1 Pa, cast into ingots weighing about 250 kg, and were roughed at the temperature range 1100-900ºC into the O.D. 75 mm bars, which were soft annealed. After making by machining the specimens they were heat treated. The specimens were austenitized on the salt bath furnace and tempered in the chamber furnace in the protective atmosphere - argon. The specimens were gradually heated to the austenitizing temperature with the isothermic stops at 650 and 850°C for 15 min. Further they were austenized for 30 min at the temperature of 1180°C and cooled in hot oil. The specimens were tempered twice after quenching, each time for 2 hours, at the temperature of 560°C and next at 545 ºC. Surfaces of specimens were sand blasted and machined on magnetic grinder.
Particular attention was paid to prevent development of micro-cracks that might disqualify the specimen from further examination. On specimens surface two parallel grooves, deep for 0.5 of triangular shape (with angle of 45°) were machined. The grooves were located along sample axis and distance between them was ca. 1.0mm. Such prepared grooves were filled with the WC, VC, TiC, SiC, Si3N4 and Al2O3 particles. Properties of the particle powders are presented in Table 2.
Therefore all experiments were made at the constant remelting rate, varying the laser beam power in the range from 0.7 to 2.1 kW. At low laser power values, i.e., 0.4 to 0.6 kW, no remelting was observed for powders mentioned above.
It was established experimentally that the argon blow-in with the flow rate of 20 l/min through the 12 mm circular nozzle oppositely directed in respect to the remelting direction provides full remelting zone protection.
The microsections' surfaces were ground on diamond wheels and next polished using the diamond buffing compounds on Struers equipment. Metallographic examinations of the material structures after laser alloying its surface layer were made on Zeiss LEICA MEF4A light microscope with magnifications from 50 to 1000x. The Leica-Qwin computer image analysis system was used for thickness examination of the particular zones of the surface layer. Structure of the developed coatings were examined with SUPRA 25 scanning electron microscope (SEM) equipped with X-ray energy dispersive spectrometer (EDS). The observation were prepared perpendicularly to the cross section of the sample no the each remelted tray. The phase composition of the investigated coatings was determined on the Panalytical X’Pert PRO diffractometer, using the filtered radiation of the cobalt anode lamp, powered with 40 kV voltage, at 20 mA heater current. The measurements were made in the angle range 30º - 110º. Hardness tests were made with Rockwell method in C scale on specimens subjected to the standard heat treatment and alloyed using the high power diode laser at various parameters, making 10 measurements for each condition and calculating their average value. Test results were analysed statistically. Hardness was measured on the ground and buffed front surfaces of specimens.
Coating microhardness was tested on the FM-700 microhardness tester. The tests were carried out at 0.05 N load, making the necessary number of indents on the section of each examined specimen, correspondingly to the structural changes depth in the material surface layer. The microhardness tests were made along the lines perpendicular to specimens’ surfaces, along the run face axis.
Table 1.
Chemical compositions of the investigated steel
Steel grade Mass concentration of the elements, %
C Cr W Mo V Co P S
HS6-5-3-8 1.28 4.2 6.3 5 3 8.4 0.002 0.022
Table 2.
Selected properties of powders
Powder Average grain size, Pm Melting point, °C Density
g/cm3 Hardness,
HV
Tungsten carbide WC 5 2770 15.6 2600
Vanadium carbide VC 1.5 2830 5.36 2850
Titanium carbide TiC 3 3140 4.25 2800
Silicon carbide SiC 7 2700 3.21 2100
Silicon nitride Si3N4 5 1900 3,44 1600
Alumina oxide Al2O3 5 2047 3.90 2300
2. Material for investigation
the HI prese proce diode The mate remeamon table suppl the la linea reliab on th lengt Remthe f makemach reme Table Spec
res 3
gradiP and t for th steels this m intera resul compthe h mechresist obtai Si3N4
phase volum techn the c leadinT
t was found out HPDL Rofin DL ented in Table 3 ess is stable is e laser (HPDL laser used is a h erials engineerin elting, and surfa ng others, of the e, movable in th
ly and coolingsy aser operation an ar spot size is its
bility, and small he material surf th (measured fro elting was carri focused beam w es it possible to o hined after rem elted layer of the
e 3.
ification of the H Laser radiation
Laser beam (continuo Power Laser beam f Laser beam spo Power de in the laser bea
3. Discus sults
Presented invest ient surface laye to supplementin his type of tool s with particles material in servi action, dislocat lts in developm plicated than in hard phases po hanical-, and tr
tance to thermal ined in particula
4 and Al2O3 part es powder used me portion in nological operat ompleted produ The main resear
ng to attaining
t in the prelimin L 020 high powe 3, that the max v = 0.5 m/min L) was used f
high power unit ng among oth face enrichment
following modu he X-Y plane, p ystems, and the nd work table p s significant adv l size. Dimensio face are 1.8 x om the protective
ied out perpend ith the multimo obtain the wide melting and all e used carbides.
HPDL Rofin DL n wavelength, nm m output power
us wave), W range, W focal length, mm ot dimensions, m
ensity range am plane, kW/cm
sion of
tigation results ers of tools in se ng the traditiona materials. Lase of hard phases m ice complicated. tion movements ment of a very c
case of the high owders. Improve ribological prop l fatigue display ar by alloying w ticles. Not only d for alloying n the matrix, ions decides the rch goal is modct.
properties of th
ary investigation r diode laser, wi imum feed rate . Rofin DL 020 for remelting t, a versatile one hers for claddi
. The laser sys ules: laser head, protective gas n computer syste ositioning. The vantage apart of ons of the laser 6.8 mm. The w e glass in the he icularly to the l de energy distri run face. The te loying, to remo
L 020 diode laser
m 8
10
m 8
mm 1
m2 0
the expe
pertain to fabri ervice at elevate al heat treatment er alloying of th
makes behaviour Superposition o s, presence of complex system h speed steels u ed abrasion we perties, and als yed by these ma
with the WC, V the right selecti but also its dis
modelled later e further service delling the grad he surface layer
ns made using ith parameters e at which the 0 high power and alloying. e, and used in ing, welding, stem consists, rotating work nozzle, power em controlling rectangular or its versatility, beam focused working focal ead) is 92 mm. longer side of ibution, which est pieces were ove the non-
r 808 r 5
2300 00-2500 82 / 32
.8 u 6.8 0.8-36.5
rimental
ication of the ed temperature t used to date he investigated r prediction of of stress fields micro-cracks, m, much more unalloyed with ear resistance, so very high terials, can be VC, TiC, SiC, on of the hard stribution and r by various e properties of dient structure impossible to
obtain by th goal of su crystalline l and metallu and service fast crystali
It was that the stru characterist morphology surface is h laser beam material tak laser beam super-fast mechanism treatment. O have been steels, who parameters
Fig. 1. Surf powder, las
Fig. 2. Bou steel alloye
he conventional uch treatment i layers, character urgical purity, wh properties of th zation due to sol revealed, basing ucture of the ma tic of occurrence y connected wit heated quickly t m acts on it and kes place, follo m has passed. Th
phase transfo m of forming th Occurrences of
confirmed in t ose thickness de and type of the
face layer edge o ser power 1.7 kW
undary of the re ed with WC pow
heat treatment. is obtaining th ristic of a signifi hich leads to grad he surface layer a lidification of me g on the metallo aterial solidifyin es of areas with th crystallisation o the temperatu d the strong circ owed by rapid s his phenomenon ormations affe he surface laye the remelted- a the surface laye pend on the em hard phases part
of the HS6-5-3-8 W
emelted surface wder, laser power
Therefore, the p he supersaturate icant chemical d dient change of h as a consequenc etal.
ographic examin ng after laser allo the gradient div n of the steel. M
re of 3420°C w culation of the solidification wh n is the reason ecting the str
ers subjected t and heat affected
ers of the inve mployed laser tre
ticles (Figs. 1-3)
8 steel alloyed w
layer of the HS r 2.1 kW
practical ed fine- diversity hardness e of the nations, oying is versified Material when the molten hen the for the ructural to laser d zones stigated eatment ).
with TiC
S6-5-3-8
185 Formation of gradient surface layers on high speed steel by laser surface alloying process
Volume 58 Issue 2 December 2012 deteriorating properties of the surface layer, like corrosion,
erosion, mechanical and thermal fatigue [27-33].
The goal of the work is to determine the technical and technological conditions for alloying the surface layer of the high speed steel HS6-5-3-8 with the high power diode laser (HPDL), and of the relationship between the parameters of laser treatment and the properties of the surface layer which increase the exploitation durability of high speed steels.
2. Material for investigation
The experiments were made on specimens made from the high speed steel HS6-5-3-8. The chemical composition of the steel is presented in Table 1. The investigated steel was molten in the electric vacuum furnace at the pressure of about 1 Pa, cast into ingots weighing about 250 kg, and were roughed at the temperature range 1100-900ºC into the O.D. 75 mm bars, which were soft annealed. After making by machining the specimens they were heat treated. The specimens were austenitized on the salt bath furnace and tempered in the chamber furnace in the protective atmosphere - argon. The specimens were gradually heated to the austenitizing temperature with the isothermic stops at 650 and 850°C for 15 min. Further they were austenized for 30 min at the temperature of 1180°C and cooled in hot oil. The specimens were tempered twice after quenching, each time for 2 hours, at the temperature of 560°C and next at 545 ºC. Surfaces of specimens were sand blasted and machined on magnetic grinder.
Particular attention was paid to prevent development of micro-cracks that might disqualify the specimen from further examination. On specimens surface two parallel grooves, deep for 0.5 of triangular shape (with angle of 45°) were machined. The grooves were located along sample axis and distance between them was ca. 1.0mm. Such prepared grooves were filled with the WC, VC, TiC, SiC, Si3N4 and Al2O3 particles. Properties of the particle powders are presented in Table 2.
Therefore all experiments were made at the constant remelting rate, varying the laser beam power in the range from 0.7 to 2.1 kW. At low laser power values, i.e., 0.4 to 0.6 kW, no remelting was observed for powders mentioned above.
It was established experimentally that the argon blow-in with the flow rate of 20 l/min through the 12 mm circular nozzle oppositely directed in respect to the remelting direction provides full remelting zone protection.
The microsections' surfaces were ground on diamond wheels and next polished using the diamond buffing compounds on Struers equipment. Metallographic examinations of the material structures after laser alloying its surface layer were made on Zeiss LEICA MEF4A light microscope with magnifications from 50 to 1000x. The Leica-Qwin computer image analysis system was used for thickness examination of the particular zones of the surface layer. Structure of the developed coatings were examined with SUPRA 25 scanning electron microscope (SEM) equipped with X-ray energy dispersive spectrometer (EDS). The observation were prepared perpendicularly to the cross section of the sample no the each remelted tray. The phase composition of the investigated coatings was determined on the Panalytical X’Pert PRO diffractometer, using the filtered radiation of the cobalt anode lamp, powered with 40 kV voltage, at 20 mA heater current. The measurements were made in the angle range 30º - 110º. Hardness tests were made with Rockwell method in C scale on specimens subjected to the standard heat treatment and alloyed using the high power diode laser at various parameters, making 10 measurements for each condition and calculating their average value. Test results were analysed statistically. Hardness was measured on the ground and buffed front surfaces of specimens.
Coating microhardness was tested on the FM-700 microhardness tester. The tests were carried out at 0.05 N load, making the necessary number of indents on the section of each examined specimen, correspondingly to the structural changes depth in the material surface layer. The microhardness tests were made along the lines perpendicular to specimens’ surfaces, along the run face axis.
Table 1.
Chemical compositions of the investigated steel
Steel grade Mass concentration of the elements, %
C Cr W Mo V Co P S
HS6-5-3-8 1.28 4.2 6.3 5 3 8.4 0.002 0.022
Table 2.
Selected properties of powders
Powder Average grain size, Pm Melting point, °C Density
g/cm3 Hardness,
HV
Tungsten carbide WC 5 2770 15.6 2600
Vanadium carbide VC 1.5 2830 5.36 2850
Titanium carbide TiC 3 3140 4.25 2800
Silicon carbide SiC 7 2700 3.21 2100
Silicon nitride Si3N4 5 1900 3,44 1600
Alumina oxide Al2O3 5 2047 3.90 2300
the HI prese proce diode The mate remeamon table suppl the la linea reliab on th lengt Remthe f makemach reme Table Spec
res 3
gradiP and t for th steels this m intera resul compthe h mechresist obtai Si3N4
phase volum techn the c leadinT
t was found out HPDL Rofin DL ented in Table 3
ess is stable is e laser (HPDL laser used is a h erials engineerin elting, and surfa ng others, of the e, movable in th
ly and coolingsy aser operation an ar spot size is its
bility, and small he material surf th (measured fro elting was carri focused beam w es it possible to o hined after rem elted layer of the
e 3.
ification of the H Laser radiation
Laser beam (continuo Power Laser beam f Laser beam spo Power de in the laser bea
3. Discus sults
Presented invest ient surface laye to supplementin his type of tool s with particles material in servi action, dislocat lts in developm plicated than in hard phases po hanical-, and tr tance to thermal ined in particula
4 and Al2O3 part es powder used me portion in nological operat ompleted produ The main resear
ng to attaining
t in the prelimin L 020 high powe 3, that the max v = 0.5 m/min L) was used f
high power unit ng among oth face enrichment
following modu he X-Y plane, p ystems, and the nd work table p s significant adv l size. Dimensio face are 1.8 x om the protective
ied out perpend ith the multimo obtain the wide melting and all e used carbides.
HPDL Rofin DL n wavelength, nm m output power
us wave), W range, W focal length, mm ot dimensions, m
ensity range am plane, kW/cm
sion of
tigation results ers of tools in se ng the traditiona materials. Lase of hard phases m ice complicated.
tion movements ment of a very c
case of the high owders. Improve ribological prop l fatigue display ar by alloying w ticles. Not only d for alloying n the matrix, ions decides the rch goal is modct.
properties of th
ary investigation r diode laser, wi imum feed rate . Rofin DL 020 for remelting t, a versatile one hers for claddi
. The laser sys ules: laser head, protective gas n computer syste ositioning. The vantage apart of ons of the laser 6.8 mm. The w e glass in the he icularly to the l de energy distri run face. The te loying, to remo
L 020 diode laser
m 8
10
m 8
mm 1
m2 0
the expe
pertain to fabri ervice at elevate al heat treatment er alloying of th makes behaviour Superposition o s, presence of
complex system h speed steels u ed abrasion we perties, and als yed by these ma
with the WC, V the right selecti but also its dis
modelled later e further service delling the grad he surface layer
ns made using ith parameters e at which the 0 high power and alloying.
e, and used in ing, welding, stem consists, rotating work nozzle, power em controlling rectangular or its versatility, beam focused working focal ead) is 92 mm.
longer side of ibution, which est pieces were ove the non-
r 808 r 5
2300 00-2500 82 / 32 .8 u 6.8 0.8-36.5
rimental
ication of the ed temperature t used to date he investigated r prediction of of stress fields micro-cracks, m, much more unalloyed with ear resistance, so very high terials, can be VC, TiC, SiC, on of the hard stribution and r by various e properties of dient structure impossible to
obtain by th goal of su crystalline l and metallu and service fast crystali
It was that the stru characterist morphology surface is h laser beam material tak laser beam super-fast mechanism treatment. O have been steels, who parameters
Fig. 1. Surf powder, las
Fig. 2. Bou steel alloye
he conventional uch treatment i layers, character urgical purity, wh properties of th zation due to sol revealed, basing ucture of the ma tic of occurrence y connected wit heated quickly t m acts on it and kes place, follo m has passed. Th
phase transfo m of forming th Occurrences of
confirmed in t ose thickness de and type of the
face layer edge o ser power 1.7 kW
undary of the re ed with WC pow
heat treatment.
is obtaining th ristic of a signifi hich leads to grad he surface layer a lidification of me g on the metallo aterial solidifyin es of areas with th crystallisation o the temperatu d the strong circ owed by rapid s
his phenomenon ormations affe he surface laye the remelted- a the surface laye
pend on the em hard phases part
of the HS6-5-3-8 W
emelted surface wder, laser power
Therefore, the p he supersaturate
icant chemical d dient change of h as a consequenc etal.
ographic examin ng after laser allo the gradient div n of the steel. M
re of 3420°C w culation of the solidification wh n is the reason ecting the str
ers subjected t and heat affected
ers of the inve mployed laser tre
ticles (Figs. 1-3)
8 steel alloyed w
layer of the HS r 2.1 kW
3 practical ed fine-
diversity hardness e of the nations, oying is versified Material when the molten hen the for the ructural to laser d zones stigated eatment ).
with TiC
S6-5-3-8
3. Discussion of the experimental
results
Fig.
Al2O affecT effec propo zone steel beamthick vanaD and A melti undis (Figs formin de harde cryst sectio (Figs chang at the axes 13).
Fig
3. Surface laye O3 powder, laser The subsequent cted zone is also ct by the surface ortional to the e thickness of 1.1 HS6-5-3-8 allo m power of 2.1 k kness of 0.28 mm dium carbide wi During alloying w
Al2O3, whose m ing points of the ssolved carbide s. 2, 5, 7). Carb
ing conglomerat ecrease of the po ening the remel allization leads on of the remelt s. 6, 9). The ch ge is observed fo e boundary betw are oriented acc
The significant
. 4. Remelted zo
er edge of the H power 1.7 kW growth of the re
connected with e of test pieces employed laser 16 mm was reve oyed with the A
kW (Fig. 4), an m is characteristi ith the laser beam with hard powde melting temperat e investigated ste powder grains i bides remain u tes (Fig. 8). Incr ortion of the und lted matrix of
to differentiati ted zone for all aracteristic repe or these areas. Sm ween the solid a
ording to the hea tly smaller size
one thickness cha
HS6-5-3-8 steel
emelting zone a h the laser radiati covered with ca power. The big ealed in case of t Al2O3 carbide w nd the smallest r
ic of the steel all m power of 0.7 k ers: WC, VC, T ture is much hi eels, penetration into the molten undissolved in
reasing the laser dissolved carbide
the steel surfac on of structure investigated allo eated crystal gro mall dendrites oc and liquid phases at transfer direct es of crystals
anges of the surf
l alloyed with
nd of the heat ion absorption arbides and is ggest remelted the high speed with the laser remelted zone loyed with the kW.
iC, SiC, Si3N4
igher than the n occurs of the steel substrate certain cases, power results es dispersively ce layer. Fast in the cross oying particles owth direction ccur in the area s, whose main ions (Figs. 11-
in this zone,
face layer of the
compared to with initiati and partly m of crystals connected w direction co gradient, a receives re equiaxial cr zone of the directions ( various me parameters.
structure is laser impact
At the l Al2O3 parti dissolve pa whereas, las investigated after the las dissolve pa laser powe concentratio concentratio the WC and in the surfa interdendrit dissolved pa
In all alloying el area of the to fluctuati remelting b along with occurring c (Fig. 8). Th waviness ap laser power of the surf because of into the stee concentratio
HS6-5-3-8 stee
o the central rem ing the solidificat melted grains of growth (cellula with retaining the orresponds with
ssuming that th emelting proces
rystals with the e fused area wh (Figs. 12). Mixi chanisms, depen Capillary lines relatively hom t on the material low laser beam p icles introduced artially originati ser power increa d steel matrix es ser alloying of st artially originatin er increase cau ons of titanium, ons in the alloye d TiC carbides pr ace layer develop tic spaces enri
articles of the all investigated ha ements was con
superfine eutect ion of the che bottom (Figs. 1 the laser power carbides’ conglo he remelting bot ppears often on r results in obtai face layer; howe
the strong liquid el are present in on grows at the
l alloyed with ha
melting area (Figs tion process on t f the native mate ar-dendritic and e privileged orien
the direction of he entire specim ss originated h
carbide lattice here heat abstrac ing of materials nding on the em s are not conne
ogeneous at low (Figs. 7, 8, 12).
power the WC, V into the surface ng clusters of ase causes their p specially at grain eel with the TiC ng conglomerate uses their parti , and tungsten
d surface layer.
resence of tungst ped by alloying (
ched in tungst loying material.
ard particles gr nfirmed at dend tics occurring in emical composit 1-3). The capill r increase which omerates form th ttom is flat in th
surface. Employ ining the maxim ever, the remelt d motions (Fig.
the remelted zo dendrites bound
ard particles wit
s. 5, 7, 9), are co the undissolved c erial. Consecutive d dendritic) are
ntation - crystals the biggest temp men's material
eat. Structure develops in the ction takes plac proceeds accor mployed laser tr cted and the re w energy values VC, TiC, SiC, Si e layer during a
carbides (Figs.
partial dissolutio n boundaries. Si C and WC these c es of carbides, ial melting, th exceed the equi In case of alloyi ten carbide was r (Figs. 14-17) an ten coming fro rades grouping drite boundaries n the remelted zo
tion, especially lary lines swirl h begin to link
he characteristic his case, howeve yment of the ma mum remelting th ting bottom get 8). Carbides intr one only; howeve daries (Figs. 14-1
h variable laser onnected
carbides e stages closely s growth perature volume of fine central e in all rding to eatment emelting s of the i3N4 and alloying 14, 16);
n in the milarly, carbides and the e local ilibrium ing with revealed d in the om the of the s in the one due at the occurs and the c swirls er slight aximum hickness ts wavy roduced er, their 17).
power
Fig. 5. Surface area of the surface layer of the HS6-5-3-8 steel after alloying with TiC powder, laser power - 1.7 kW
Fig. 6. Small eutectic in the surface layer of the HS6-5-3-8steel after laser alloying with TiC carbide, laser power 2.1 kW
Fig. 7. Alloying material and small eutectic in the surface layer of the HS6-5-3-8 steel after laser alloying with WC carbide, laser power 2.1 kW
Fig. 8. Alloying material in the surface layer of the HS6-5-3-8 steel after laser alloying with WC powder, laser power 2.1 kW
Fig. 9. Surface area of the surface layer of the HS6-5-3-8 steel after alloying with Al2O3 powder, laser power - 0.7 kW
Fig. 10. Boundary of the remelted zone in the surface layer of the HS6-5-3-8 steel after laser alloying with Al2O3 powder, laser power 0.7 kW
187 Formation of gradient surface layers on high speed steel by laser surface alloying process
Volume 58 Issue 2 December 2012 Fig.
Al2O affecT effec propo zone steel beamthick vanaD and A melti undis (Figs formin de harde cryst sectio (Figs chang at the axes 13).
Fig
3. Surface laye O3 powder, laser The subsequent cted zone is also ct by the surface ortional to the e thickness of 1.1 HS6-5-3-8 allo m power of 2.1 k kness of 0.28 mm dium carbide wi During alloying w
Al2O3, whose m ing points of the ssolved carbide s. 2, 5, 7). Carb
ing conglomerat ecrease of the po ening the remel allization leads on of the remelt s. 6, 9). The ch ge is observed fo e boundary betw are oriented acc
The significant
. 4. Remelted zo
er edge of the H power 1.7 kW growth of the re
connected with e of test pieces employed laser 16 mm was reve oyed with the A
kW (Fig. 4), an m is characteristi ith the laser beam
with hard powde melting temperat e investigated ste powder grains i bides remain u tes (Fig. 8). Incr ortion of the und lted matrix of
to differentiati ted zone for all aracteristic repe or these areas. Sm ween the solid a
ording to the hea tly smaller size
one thickness cha
HS6-5-3-8 steel
emelting zone a h the laser radiati covered with ca power. The big ealed in case of t Al2O3 carbide w nd the smallest r
ic of the steel all m power of 0.7 k ers: WC, VC, T ture is much hi eels, penetration into the molten undissolved in
reasing the laser dissolved carbide
the steel surfac on of structure investigated allo eated crystal gro mall dendrites oc and liquid phases at transfer direct es of crystals
anges of the surf
l alloyed with
nd of the heat ion absorption arbides and is ggest remelted the high speed with the laser remelted zone loyed with the kW.
iC, SiC, Si3N4
igher than the n occurs of the steel substrate certain cases, power results es dispersively ce layer. Fast in the cross oying particles owth direction ccur in the area s, whose main ions (Figs. 11-
in this zone,
face layer of the
compared to with initiati and partly m of crystals connected w direction co gradient, a receives re equiaxial cr zone of the directions ( various me parameters.
structure is laser impact
At the l Al2O3 parti dissolve pa whereas, las investigated after the las dissolve pa laser powe concentratio concentratio the WC and in the surfa interdendrit dissolved pa
In all alloying el area of the to fluctuati remelting b along with occurring c (Fig. 8). Th waviness ap laser power of the surf because of into the stee concentratio
HS6-5-3-8 stee
o the central rem ing the solidificat melted grains of growth (cellula with retaining the orresponds with
ssuming that th emelting proces
rystals with the e fused area wh (Figs. 12). Mixi chanisms, depen Capillary lines relatively hom t on the material low laser beam p icles introduced artially originati ser power increa d steel matrix es ser alloying of st artially originatin
er increase cau ons of titanium, ons in the alloye d TiC carbides pr ace layer develop tic spaces enri
articles of the all investigated ha ements was con superfine eutect ion of the che bottom (Figs. 1 the laser power carbides’ conglo he remelting bot ppears often on r results in obtai face layer; howe
the strong liquid el are present in on grows at the
l alloyed with ha
melting area (Figs tion process on t f the native mate ar-dendritic and e privileged orien
the direction of he entire specim ss originated h
carbide lattice here heat abstrac ing of materials nding on the em s are not conne
ogeneous at low (Figs. 7, 8, 12).
power the WC, V into the surface ng clusters of ase causes their p specially at grain eel with the TiC ng conglomerate uses their parti , and tungsten
d surface layer.
resence of tungst ped by alloying ( ched in tungst loying material.
ard particles gr nfirmed at dend tics occurring in emical composit 1-3). The capill r increase which omerates form th ttom is flat in th
surface. Employ ining the maxim
ever, the remelt d motions (Fig.
the remelted zo dendrites bound
ard particles wit
s. 5, 7, 9), are co the undissolved c erial. Consecutive d dendritic) are
ntation - crystals the biggest temp men's material
eat. Structure develops in the ction takes plac
proceeds accor mployed laser tr cted and the re w energy values VC, TiC, SiC, Si e layer during a
carbides (Figs.
partial dissolutio n boundaries. Si C and WC these c
es of carbides, ial melting, th exceed the equi In case of alloyi ten carbide was r (Figs. 14-17) an ten coming fro rades grouping drite boundaries n the remelted zo
tion, especially lary lines swirl h begin to link he characteristic his case, howeve yment of the ma mum remelting th ting bottom get 8). Carbides intr one only; howeve daries (Figs. 14-1
h variable laser onnected
carbides e stages closely s growth perature volume of fine central e in all rding to eatment emelting s of the i3N4 and alloying 14, 16);
n in the milarly, carbides and the e local ilibrium ing with revealed d in the om the of the s in the one due at the occurs and the c swirls er slight aximum hickness ts wavy roduced er, their 17).
power
5 Fig. 5. Surface area of the surface layer of the HS6-5-3-8 steel
after alloying with TiC powder, laser power - 1.7 kW
Fig. 6. Small eutectic in the surface layer of the HS6-5-3-8steel after laser alloying with TiC carbide, laser power 2.1 kW
Fig. 7. Alloying material and small eutectic in the surface layer of the HS6-5-3-8 steel after laser alloying with WC carbide, laser power 2.1 kW
Fig. 8. Alloying material in the surface layer of the HS6-5-3-8 steel after laser alloying with WC powder, laser power 2.1 kW
Fig. 9. Surface area of the surface layer of the HS6-5-3-8 steel after alloying with Al2O3 powder, laser power - 0.7 kW
Fig. 10. Boundary of the remelted zone in the surface layer of the HS6-5-3-8 steel after laser alloying with Al2O3 powder, laser power 0.7 kW
Fig. 11. Edge of the alloyed surface layer of the HS6-5-3-8 steel after laser alloying with TiC powder, laser power 1.7 kW
Fig. 12. Boundary of the remelted zone in the surface layer of the HS6-5-3-8 steel after laser alloying with WC powder, laser power 1.7 kW
Fig. 13. Boundary of the remelted zone in the surface layer of the HS6-5-3-8 steel after laser alloying with Al2O3 powder, laser power 1.7 kW
Fig. 14. Small eutectic in the surface layer of the HS6-5-3-8 steel after laser alloying with WC carbide, laser power 0.7 kW
Fig. 15. EDS point-wise analysis of the HS6-5-3-8 steel sample after laser alloying with WC powder, laser power 0.7 kW
Fig. 16. Small eutectic in the surface layer of the HS6-5-3-8 steel after laser alloying with TiC carbide, laser power 1.7 kW
Fig. after resulL poweexam zonesizes partic 9 to 3 fromconv 266 cryst the e partia hardnL achie connzone thick radia the m the s powe
17. EDS point- laser alloying w Laser alloying
lts in structure er range, whic mple (Fig. 18). G
s of the surface s in the remelted cular particles in 32 µm2, TiC from m 17 to 27 µm2 a
ventionally heat µm2; therefore tallization front, elongated and s al melting and re Laser treatment
ness increase o eved thanks t nected closely w . The factor con kness of the re ation energy and material. Only th surface layer w er of the laser b
Fig. 18. Av
wise analysis o with TiC powder with all of the
refinement in ch is presented Grains of varying
layer after lase d zone of the in n the ranges: WC m 6 to 12 µm2, S and Si3N4 from 2
treated stel the e, it is 5-10
between the fu maller grains o e-crystallization of surface layer of all investigat to occurrences with the heat rem
ntrolling in grea emelted layer, d the time period
he laser power a with the constan beam the remelt
verage grain size
f the HS6-5-3-8 , laser power 1.7 e above mentio the entire inve d with the HS g sizes occur in er alloying. The nvestigated stee C from 8 to 31 µ SiC from 15 to 2 21 to 44 µm2. Ho average grain times bigger. used and heat a occur, which are
during laser trea rs results in the ted steels and
of phase tr moval rate from at measure the c dependant on d of the laser be affects the energ nt remelting rate
ting depth is sm
e in the remeltin
8 steel sample 7 kW oned particles estigated laser S6-5-3-8 steel the particular average grain els are for the µm2, VC from 26 µm2, Al2O3
owever, in the size is 240 to Only at the ffected zones, e subjected to
atment. e steel surface
this effect is ransformations m the remelted cooling rate is the absorbed eam impact on gy delivered to e. At the low mall; therefore
g area of the HS
heat remov occurrences fine-grained responsible surface lay carbides, its laser beam on the hard the hard ph hardness w standard he alloying of particles h compared t
Figures hardness ch layer of the alloyed wit occurs at th test pieces obtained at the Ti carb of the steel remelted ar alloying wi drop attests laser treatm tempering t fused carbi demonstrati reason of th the remelte the laser p demonstrate hot work al or its disper carbides, w with the al hardness in properties o steel takes steel after th
S6-5-3-8 steel all
val rate is the s of the super-fa d martensite e for hardness gr yer reveals the s maximum hard
power equal to dness tests of th hases powders t was improved, c eat treatment onl f this steel, i.e.: hardness of th o the steel after s 20-23 presen hanges dependi e investigated st th carbides the v he surface layer
of steels subject t the laser powe bide; whereas, th l are characterist rea in the laser ith the variable s to developmen ment, heated t temperature. Oc ides and lattice ing hardness di he microhardnes
d zone and the a aths versus dist ed that as a resu lloy tool steels u rsive hardening with the simultan
lloying additive ncrease occurs of the surface l
place, compare he conventional
loyed with hard
e highest. High ast phase transfo
structure occu rowth. The highe HS6-5-3-8 stee dness growth to
2.1 kW (Fig. 19 e steel subjected that for most of
ompared to the y. In case of the WC, VC, TiC, he surface lay the standard hea nts the flow of ing on the dist
teels. In case of visible gradient r. The highest m
ted to laser treat er of 1.4 kW for he gradient layer tic of the similar power range fro particles (Figs. nt of the tempere
to the tempera currences in the of carbides at fferent from the ss measurement alloyed one on th tance from the ult of remelting using the HPDL by the innudated neous enrichme s coming from and improveme layer of the las ed to the analog
heat treatment.
particles, laser p
h cooling rate rmations; theref urs in the m
est hardness of t el alloyed with 73.6 HRC occur 9). One can stat d to laser alloyin f the powders th e steel subjected other carbides u , SiC, Si3N4 and er grows mod at treatment.
f the gradient ance from the f all investigate micro-hardness micro-hardness f tment of 1331 H r the alloyed ste rs obtained by a r micro-hardnes om 0.7 to 2.1 kW
21, 22). The h ed material zone ature higher th structure of the
dendrites’ boun e substrate, feat
results discrepa he transverse sec
surface. Investi the surface laye high power diod d, or partially di ent of the surfac the disolving c ent of the tribo er remelted or gous properties
power 2.1 kW
causes fore, the material, the steel the Ti rs at the te based ng with he steel d to the used for d Al2O3
derately micro- surface d steels growth from all HV0.01 is eel with alloying ss in the W after hardness e during han the e graded ndaries, ture the ancy for ction of igations er of the de laser issolved ce layer carbides ological alloyed of this
189 Formation of gradient surface layers on high speed steel by laser surface alloying process
Volume 58 Issue 2 December 2012 Fig. 11. Edge of the alloyed surface layer of the HS6-5-3-8 steel
after laser alloying with TiC powder, laser power 1.7 kW
Fig. 12. Boundary of the remelted zone in the surface layer of the HS6-5-3-8 steel after laser alloying with WC powder, laser power 1.7 kW
Fig. 13. Boundary of the remelted zone in the surface layer of the HS6-5-3-8 steel after laser alloying with Al2O3 powder, laser power 1.7 kW
Fig. 14. Small eutectic in the surface layer of the HS6-5-3-8 steel after laser alloying with WC carbide, laser power 0.7 kW
Fig. 15. EDS point-wise analysis of the HS6-5-3-8 steel sample after laser alloying with WC powder, laser power 0.7 kW
Fig. 16. Small eutectic in the surface layer of the HS6-5-3-8 steel after laser alloying with TiC carbide, laser power 1.7 kW
Fig.
after resulL poweexam zonesizes partic 9 to 3 fromconv 266 cryst the e partia hardnL achie connzone thick radia the m the s powe
17. EDS point- laser alloying w Laser alloying lts in structure er range, whic mple (Fig. 18). G
s of the surface s in the remelted
cular particles in 32 µm2, TiC from m 17 to 27 µm2 a
ventionally heat µm2; therefore tallization front, elongated and s al melting and re Laser treatment
ness increase o eved thanks t nected closely w . The factor con kness of the re ation energy and material. Only th surface layer w er of the laser b
Fig. 18. Av
wise analysis o with TiC powder with all of the
refinement in ch is presented Grains of varying
layer after lase d zone of the in n the ranges: WC m 6 to 12 µm2, S and Si3N4 from 2
treated stel the e, it is 5-10
between the fu maller grains o e-crystallization of surface layer of all investigat to occurrences with the heat rem
ntrolling in grea emelted layer, d the time period he laser power a with the constan beam the remelt
verage grain size
f the HS6-5-3-8 , laser power 1.7 e above mentio the entire inve d with the HS g sizes occur in er alloying. The nvestigated stee C from 8 to 31 µ SiC from 15 to 2 21 to 44 µm2. Ho average grain times bigger.
used and heat a occur, which are
during laser trea rs results in the ted steels and
of phase tr moval rate from at measure the c dependant on d of the laser be affects the energ nt remelting rate
ting depth is sm
e in the remeltin
8 steel sample 7 kW oned particles estigated laser S6-5-3-8 steel the particular average grain els are for the µm2, VC from 26 µm2, Al2O3
owever, in the size is 240 to Only at the ffected zones, e subjected to
atment.
e steel surface this effect is ransformations m the remelted cooling rate is the absorbed eam impact on gy delivered to e. At the low mall; therefore
g area of the HS
heat remov occurrences fine-grained responsible surface lay carbides, its laser beam on the hard the hard ph hardness w standard he alloying of particles h compared t
Figures hardness ch layer of the alloyed wit occurs at th test pieces obtained at the Ti carb of the steel remelted ar alloying wi drop attests laser treatm tempering t fused carbi demonstrati reason of th the remelte the laser p demonstrate hot work al or its disper carbides, w with the al hardness in properties o steel takes steel after th
S6-5-3-8 steel all
val rate is the s of the super-fa d martensite e for hardness gr yer reveals the s maximum hard
power equal to dness tests of th
hases powders t was improved, c eat treatment onl f this steel, i.e.:
hardness of th o the steel after s 20-23 presen hanges dependi e investigated st th carbides the v he surface layer of steels subject t the laser powe bide; whereas, th l are characterist rea in the laser ith the variable s to developmen ment, heated t temperature. Oc ides and lattice
ing hardness di he microhardnes d zone and the a aths versus dist ed that as a resu lloy tool steels u rsive hardening with the simultan
lloying additive ncrease occurs of the surface l
place, compare he conventional
loyed with hard
e highest. High ast phase transfo
structure occu rowth. The highe HS6-5-3-8 stee dness growth to 2.1 kW (Fig. 19 e steel subjected that for most of
ompared to the y. In case of the WC, VC, TiC, he surface lay the standard hea nts the flow of ing on the dist
teels. In case of visible gradient r. The highest m ted to laser treat er of 1.4 kW for he gradient layer tic of the similar power range fro particles (Figs.
nt of the tempere to the tempera currences in the
of carbides at fferent from the ss measurement alloyed one on th
tance from the ult of remelting using the HPDL by the innudated neous enrichme s coming from and improveme layer of the las ed to the analog
heat treatment.
particles, laser p
h cooling rate rmations; theref urs in the m est hardness of t el alloyed with 73.6 HRC occur 9). One can stat d to laser alloyin f the powders th e steel subjected
other carbides u , SiC, Si3N4 and er grows mod at treatment.
f the gradient ance from the f all investigate micro-hardness micro-hardness f tment of 1331 H r the alloyed ste rs obtained by a r micro-hardnes om 0.7 to 2.1 kW
21, 22). The h ed material zone ature higher th structure of the dendrites’ boun e substrate, feat
results discrepa he transverse sec
surface. Investi the surface laye high power diod d, or partially di ent of the surfac the disolving c ent of the tribo er remelted or gous properties
power 2.1 kW
causes fore, the material, the steel the Ti rs at the te based ng with he steel d to the used for d Al2O3
derately micro- surface d steels growth from all HV0.01 is eel with alloying ss in the W after hardness e during han the e graded ndaries, ture the ancy for ction of igations er of the de laser issolved ce layer carbides ological alloyed of this
