Sliding Wear Behavior of Spark Plasma-Sintered Cu–6 Wt Pct Cr Alloy at Room and Elevated Temperatures

Abstract

Although dilute Cu-Cr alloys are frequently used for applications involving sliding contacts, their wear mechanism at elevated temperatures has rarely been explored. We fabricated a bulk Cu-6 wt pct Cr alloy using high-energy ball milling and spark plasma sintering, and systematically investigated its dry sliding wear behavior against 440C stainless steel at room temperature and 300 °C. The alloy had a heterogeneous microstructure consisting of coarse-grained Cu (average grain size: 1.5 µm) distributed into a nanocrystalline Cu-Cr matrix (average Cu grain size: 77 nm; Cr-rich precipitate size: 18 nm), which gave high strength and plasticity (ultimate compressive strength: 1020 MPa; strain-to-failure: 26.0 pct) at room temperature. At 300 °C, the strength was significantly reduced, the coefficient of friction and wear rate increased, and the dominant wear mode switched from adhesive wear to oxidative/abrasive wear. Uniformly distributed nanoscale Cr-rich and Cr oxide precipitates hindered severe plastic deformation near the sliding surface during wear at room temperature; at 300 °C, severe plastic deformation was observed, with elongated Cu grains and uniformly dispersed Cr-rich and Cr oxide nanoparticles. Formation of a discontinuous glaze layer consisting of equiaxed nanograins of Cu, Cu oxides, and Cr oxides resulted in severe abrasion-assisted wear, and reduced the wear resistance at 300 °C.