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

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

    Research output: Contribution to journalArticleScientificpeer-review

    4 Citations (Scopus)

    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, self-mated 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.
    Original languageEnglish
    Pages (from-to)1222-1232
    JournalWear
    Volume426-427
    Issue numberPart B
    DOIs
    Publication statusPublished - Apr 2019
    MoE publication typeA1 Journal article-refereed
    Event22nd International Conference on Wear of Materials - Hyatt Regency Miami, Miami, United States
    Duration: 14 Apr 201919 Apr 2019

    Keywords

    • Stellite
    • Cobalt-based alloys
    • Electron backscatter diffraction
    • nuclear
    • HIP

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