Effect of CaF2 nanoparticles on the microstructure evolution, mechanical properties and tribological behavior of Cu-Ni alloy/cBN self-lubricating composites

This research study presents the effect of CaF2 reinforcement on the microstructure, mechanical and self-lubricating (SL) tribological properties of Cu-Ni alloy/cBN metal matrix composite (MMC). The composite of Cu-Ni (CN) alloy/cBN reinforced with CaF2 nanoparticles (2–6 wt%) was developed by powder metallurgy, using pressure-less sintering without any additive. Microstructure studies proved uniform dispersion of cBN/ CaF2 particles in the Cu-Ni matrix. The maximum density and hardness were obtained at reinforcement of 2 wt% CaF2. The minimum coefficient of friction (0.15) and higher wear resistance were obtained for 4 wt% CaF2 reinforcement in CN alloy/cBN composite. Tribo-chemical reactions culminated in the formation of oxides of Cu, Ni, Fe and B at the interface, which significantly influenced the tribological properties and wear mechanisms. The worn surface analysis indicated that adhesive wear, oxidative wear and delamination are the predominated wear mechanism of CN alloy-cBN-CaF2 composite.