Comparison of the sliding wear behaviour of self-mated HIPed Stellite 3 and Stellite 6 in a simulated PWR water environment

Ratia, Vilma L; Zhang, Deen; Carrington, Matthew J.; Daure, Jaimie L.; McCartney, D. Graham; Shipway, Philip H.; Stewart, David A.

Abstract

Cobalt-based alloys such as Stellite 3 and Stellite 6 are widely used to protect stainless steel surfaces in primary circuit nuclear reactor applications where high resistance to wear and corrosion are required. In this study, selfmated sliding wear of Stellite 3 and Stellite 6 consolidated by hot isostatic pressing were compared. Tests were performed with a pin-on-disc apparatus enclosed in a water-submerged autoclave environment and wear was measured from room temperature up to 250 °C (a representative pressurized water reactor environment). Both alloys exhibit a microstructure of micron-sized carbides embedded in a cobalt-rich matrix. Stellite 3 (higher tungsten and carbon content) contains M7C3 and an eta (η) -carbide whereas Stellite 6 contains only M7C3. Furthermore, the former has a significantly higher carbide volume fraction and hardness than the latter. Both alloys show a significant increase in the wear rate as the temperature is increased but Stellite 3 has a higher wear resistance over the entire range; at 250 °C the wear rate of Stellite 6 is more than five times that of Stellite 3. There is only a minimal formation of a transfer layer on the sliding surfaces but electron backscatter diffraction on cross-sections through the wear scar revealed that wear causes partial transformation of the cobalt matrix from fcc to hcp in both alloys over the entire temperature range. It is proposed that the acceleration of wear with increasing temperature in the range studied is associated with a tribocorrosion mechanism and that the higher carbide fraction in Stellite 3 resulted in its reduced wear rate compared to Stellite 6.

Citation

Ratia, V. L., Zhang, D., Carrington, M. J., Daure, J. L., McCartney, D. G., Shipway, P. H., & Stewart, D. A. (2019). Comparison of the sliding wear behaviour of self-mated HIPed Stellite 3 and Stellite 6 in a simulated PWR water environment. Wear, 426-427(Part B), 1222-1232. https://doi.org/10.1016/j.wear.2019.01.116

• Journal Article Type: Article
• Acceptance Date: Jan 22, 2019
• Online Publication Date: Apr 10, 2019
• Publication Date: Apr 30, 2019
• Deposit Date: Mar 7, 2019
• Publicly Available Date: Apr 10, 2019
• Journal: Wear
• Print ISSN: 0043-1648
• Electronic ISSN: 1873-2577
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 426-427
• Issue: Part B
• Pages: 1222-1232
• DOI: https://doi.org/10.1016/j.wear.2019.01.116
• Keywords: Stellite; cobalt-based alloys; electron backscatter diffraction; nuclear; HIP
• Public URL: https://nottingham-repository.worktribe.com/output/1615396
• Publisher URL: https://www.sciencedirect.com/science/article/pii/S004316481930211X
• Additional Information: This article is maintained by: Elsevier; Article Title: Comparison of the sliding wear behaviour of self-mated HIPed Stellite 3 and Stellite 6 in a simulated PWR water environment; Journal Title: Wear; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.wear.2019.01.116; Content Type: article; Copyright: © 2019 The Authors. Published by Elsevier B.V.
• Contract Date: Mar 7, 2019