In Situ and Ex Situ Analysis of the Reciprocating Sliding Wear Behavior of Cold Sprayed CrMnCoFeNi Cantor HEA Coatings in Dry Air and Ambient Air Conditions
Maya M. Harfouche, Sima A. Alidokht, Richard R. Chromik
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引用次数: 0
Abstract
This study examined and compared the tribological properties of a cold-sprayed CrMnCoFeNi high entropy alloy (Cantor alloy) coating under ambient and dry air conditions. Tribological testing was conducted using an in situ tribometer equipped with video microscopy, allowing real-time monitoring of the evolution of the sliding interfaces through a transparent sapphire counterface. This experimental setup provided the opportunity to observe phenomena that would otherwise remain concealed between the contacting bodies. The wear rate was 1.8 ± 0.5 × 10⁻4 mm3/Nm in ambient air and 7.5 ± 0.7 × 10⁻4 mm3/Nm in dry air. In dry air, the velocity accommodation mode was characterized by interfacial sliding of a static transfer film against the wear track, resulting in a stable steady-state coefficient of friction (CoF) of 0.5. In contrast, ambient air conditions led to an average CoF of 0.8, with fluctuations attributed to plastic shearing of the transfer film observed in situ. The higher humidity in ambient air inhibited cold welding of wear particles, resulting in a less stable transfer film that underwent removal or extrusion events, which were associated with sudden drops in CoF. Additionally, a “metal debris” oxide formation mechanism was observed in ambient air, contributing to the formation of a protective tribofilm and a reduction in the wear rate. In dry air, the “oxidation-scrape-reoxidation” mechanism dominated, facilitated by the absence of adsorbed water droplets. This resulted in an increased wear rate under dry conditions.
期刊介绍:
Tribology Letters is devoted to the development of the science of tribology and its applications, particularly focusing on publishing high-quality papers at the forefront of tribological science and that address the fundamentals of friction, lubrication, wear, or adhesion. The journal facilitates communication and exchange of seminal ideas among thousands of practitioners who are engaged worldwide in the pursuit of tribology-based science and technology.