Cyclic oxidation of Haynes 230 alloy
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The cyclic oxidation of Haynes 230 alloy (Ni-Cr-W-Mo alloy) was investigated in air at three different temperatures, 871, 982 and 1093 °C. Studies indicated that during cyclic oxidation, protective scales formed which were predominantly Cr2O3, with Kirkendall voids formed both at the scale/alloy interface and grain boundaries. Intergranular oxides were observed at temperatures above 982 °C while internal oxide particles were found above 1093 °C. Both intergranular and internal oxides were identified as aluminium oxide. A 50 μm chromium-depleted zone developed after 70 h exposure at 1093 °C and was accompanied by disastrous scale spalling. The lowest chromium concentration within the depleted zone was 14 wt% which still provided a sufficient supply of chromium for development of a continuous Cr2O3 rich scale. Decarburization was observed at the higher temperature of 1093 °C, and a carbide-free zone developed. Also, it was found that Haynes 230 is subject to a sensitization process. At the lower exposure temperature of 871 °C, large amounts of chromium carbide formed preferentially at the grain boundaries. While at the surface region chromium carbide precipitation occurred at the twin boundaries.
KeywordsTwin Boundary Decarburization Internal Oxide Chromium Concentration Chromium Carbide
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- 1.D. P. Whittle and H. Hindam, in “Corrosion-Erosion-Wear of Materials in Emerging Fossil Energy Systems”, edited by A. V. Levy (NACE, Houston, TX, 1982).Google Scholar
- 2.G. C. Wood and F. H. Stott, in “Proceedings of NACE Conference on High Temperature Corrosion”, San Diego, March 1981.Google Scholar
- 4.P. Elliott, Mater. Perform.4 (1989) 57.Google Scholar
- 5.N. Birks and G. H. Meier, “Introduction to High Temperature Oxidation of Metals” (Arnold, London, 1983) pp. 107–24.Google Scholar
- 14.P. Kofstad, “High Temperature Corrosion” (Eisevier Applied Science, London, 1988) pp. 339, 362.Google Scholar
- 15.M. A. Streicher, in “Stainless Steel '77”, edited by R. Q. Barr (AMAX, London, 1977) pp. 1–34.Google Scholar