Effect of temperature on tribo-oxide formation and the fretting wear and friction behavior of zirconium and nickel-based alloys

• Published in: Wear Vol. 476; p. 203722
• Main Authors: Attia, M. Helmi, de Pannemaecker, Alix, Williams, Gary
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.07.2021; Elsevier Science Ltd
• Subjects: Abrasive wear; Abrasives; Adhesive strength; Adhesive wear; Chromium oxides; Coefficient of friction; Fatigue cracks; Fretting; Fretting wear; Friction; Glazing; Iron oxides; Microcracks; Nickel alloy 718; Nickel base alloys; Nickel oxides; Nuclear power plants; Nuclear safety; Raman spectroscopy; Room temperature; Solid lubricants; Substrates; Surface layers; Temperature effects; Transition temperature; Tribology; Wear mechanisms; Wear particles; Zirconium alloy; Zirconium alloys; Zirconium base alloys; Zirconium alloy; Transition temperature; Nickel alloy 718; Fretting wear
• ISSN: 0043-1648; 1873-2577
• DOI: 10.1016/j.wear.2021.203722

Fretting wear damage in nuclear power plants is a safety and economic concern. Therefore, understanding the effect of operating conditions on the wear mechanism is essential for optimum design. Fretting tests were performed on a nickel-based alloy 718 against a zirconium alloy in the range 25 °C < T < 315 °C. The effect of temperature was investigated by examining the tribo-surface oxides, using SEM, EDX, and Raman spectroscopy. Compared to room temperature, results showed that the wear coefficient of zirconium alloy increases significantly at a transition temperature Ttr ~250–260 °C, which is consistent with published data. A similar trend was observed for the friction coefficient. At Ttr, a thick layer of zirconium was transferred and adhered to the mating Ni alloy. In addition to adhesive wear, the generation of subsurface micro-cracks caused delamination and fatigue disruption. The high hardness of the fragmented wear debris caused abrasive wear, promoting the observed high wear coefficient. At T = 315 °C, which is above the glazing temperature of the mating Ni alloy, the oxidized surface layer ZrO2 was thinner and adherent to the substrate, acting as solid lubricant. On the mating Ni alloy surface, the detected zirconium oxide (ZrO2), nickel oxide (NiO) glaze, iron and chromium oxide (CrFeO3) contributed to the lower fretting wear and friction coefficients. The wear coefficient of the Ni alloy was found to decrease monotonically with temperature. At room temperatures, NiO oxide particles acted as loose abrasives. The presence of iron oxide (Fe2O3) contributed also to the reduced tribological performance. At T = 315 °C, the formation of a protective compact oxide glaze acted as a self-repairing solid lubricant, contributing to the relatively low fretting wear coefficient, which is further enhanced by the presence of CrFeO3 oxide. •There is a transition temperature Ttr around 250 °C, at which the wear coefficient of Zr alloy increases significantly.•At Ttr, the generation of subsurface micro-cracks of the Zr alloy caused delamination and fatigue disruption.•At T>Ttr, glaze formed on Ni alloy 718 and the presence of ZrO2, NiO, and CrFeO3 reduce wear and friction coefficients.•A summary of the tribo-oxides formed on the Zr- and the Ni-alloys in the temperature range of 25 < T < 315 °C is tabulated.