ABSTRACT
High-temperature processes and applications require their associated components to reach elevated temperatures that produce consequences on material properties. Hightemperature oxidation is one such consequence and results from chemical reactions with the surrounding environment. Depending on severity, material performance can
CONTENTS
5.1 Introduction .......................................................................................................................... 95 5.2 Experimental Considerations .............................................................................................99 5.3 Major Features of High-Temperature Oxidation and Corrosion ................................ 102
5.3.1 Overview ................................................................................................................. 102 5.3.3 Metals, Alloys, and Intermetallics ....................................................................... 106
5.3.3.1 Copper Alloys .......................................................................................... 108 5.3.3.2 Iron Alloys (Steels) .................................................................................. 109 5.3.3.3 High-Temperature Nickel-Based Alloys .............................................. 110 5.3.3.4 Intermetallic Aluminide and Silicide Compounds ............................ 117 5.3.3.5 Refractory Metals and Silicide Coatings ............................................. 121 5.3.3.6 MAX Compounds ................................................................................... 123
5.4 Oxidation of SiO2-Forming Ceramic Materials ............................................................. 123 5.4.1 Passive Oxidation ................................................................................................... 123
5.4.1.1 Oxidation in H2O/O2 .............................................................................. 127 5.4.2 Active Oxidation .................................................................................................... 130 5.4.3 SiC-Based Composites ........................................................................................... 134
5.5 Corrosion in Complex Gas/Deposit Environments...................................................... 136 5.5.1 Corrosion in Mixed Gases .................................................................................... 136 5.5.2 Hot Corrosion of Alloys ........................................................................................ 137
5.5.2.1 Type I Hot Corrosion .............................................................................. 137 5.5.2.2 Type II Hot Corrosion ............................................................................. 139 5.5.2.3 Hot Corrosion of SiC and Si3N4 Ceramics ........................................... 143 5.5.2.4 CMAS and Volcanic Ash Considerations ............................................ 144
5.6 Re-Entry Materials ............................................................................................................. 148 5.7 Closing Remarks ................................................................................................................ 153 Acknowledgments ...................................................................................................................... 154 References ..................................................................................................................................... 154
be degraded by surface recession or internal embrittlement, placing limits on use temperatures and times. Coatings, cooling schemes, or gas modifications are often employed to counteract these effects and provide a safer operational envelope. The purpose of this chapter is to provide a general description of the physical process, with specific examples chosen to highlight the prominent classes of high-temperature materials. It is hoped it will serve as a brief introduction and overview. For more detailed treatment of fundamentals and a broader list of topics, the reader is referred to classic texts (Kofstad 1988; Lai 1990; Birks, Meier et al. 2006; Young 2008). More detailed reviews can also be found in the latest edition of Shreir’s Corrosion, 2009. Here, dedicated chapters are found for defects and diffusion in oxide scales, stress effects, sulfidation, steam, and molten salt corrosion, steels, alumina and chromia scale forming alloys, coatings, intermetallics, and ceramics (Cottis et al. 2009).
