Doctoral thesis Microstructure of laser clad Ni-Cr-Mo-W coatings and their high
Damian Koclęga temperature corrosion resistance
~ 3 ~
Table of Contents:
Index of abbreviations and symbols ...5
Acknowledges ...6
Podsumowanie ...7
Summary ...8
I. Introduction ... 9
II. Literature review ... 10
2.1 Basic concept of laser cladding ...10
2.2 High-temperature corrosion ...17
2.2.1 Thermodynamics of oxide scale formation ...18
2.2.2 Kinetic models for the oxidation of metals ...20
2.2.3 Oxide scale formation ...22
2.2.4 The Wagner theory ...24
2.2.5 Oxidation of alloys ( Ni - based chromium oxide forming alloys) ...31
2.2.6 Diffusion and mass transport ...32
2.2.7 Corrosion in sulfur atmosphere, sulphidation ...39
2.2.8 Corrosion in ash atmosphere ...42
2.3 Material use in fossil fuel power plants ...44
2.3.1 Ferrite - iron based steels used in power plants ...47
2.3.2 Austenitic steels ...52
2.3.3 Ni-based alloys and coatings ...57
III. Own research ...61
3.1 Thesis target ...61
3.2 Methodology of research ...63
3.3 Experimental procedure ...66
IV. Results of investigations ... 71
4.1 Characterization of 13CrMo4-5 steel and Ni-Cr-Mo-W coatings ...71
4.2 Characterization of the oxide scales formed on the coatings surface after corrosion tests ...79
4.2.1 Oxidation of Ni-Cr-Mo-W coatings - short term corrosion test ...79
4.2.2 Influence of corrosion environments on two-layers clads and steel 13CrMo4-5 ..87
Doctoral thesis Microstructure of laser clad Ni-Cr-Mo-W coatings and their high
Damian Koclęga temperature corrosion resistance
~ 4 ~
4.3.1 Transmission electron microscopy observations after gas corrosion of the
Ni-based coatings ...97
4.3.2 The X-ray diffractions of the Ni-Cr-Mo-W clads ...109
4.3.3 The X-ray photoelectron spectroscopy of the clads after gas corrosion ...111
4.3.4 The mass change of the Ni-Cr-Mo-W clads after gas corrosion ...116
4.4 Corrosion in a gas and ash environment ...117
V. Discussion ... 133
5.1 Oxidation of the Ni-Cr-Mo-W clads ...134
5.2 Gas corrosion of the Ni-Cr-Mo-W clads ...139
5.3 Gas corrosion with ash deposition of the Ni-Cr-Mo-W clads ...146
5.4 Thermodynamic calculations of the phases stability formed after corrosion tests in a gas environment and gas with ash deposit ...153
5.5 Comparison between gas corrosion and gas corrosion with ash deposition ...162
VI. Conclusions ...164
