Tribological behaviour of Cu based materials produced by mechanical milling/alloying and spark plasma sintering

Aim of the work is to investigate the tribological behaviour of Cu based materials produced by mechanical milling (MM), mechanical alloying (MA) and finally sintered by Spark Plasma Sintering (SPS). MM causes a significant strain hardening of Cu, while MA by 0.5 wt%TiB2 adds a further dispersion hardening contribution. During dry sliding contact against high speed steel a close relation has been found between friction coefficient and contact temperature highlighting two regimes. The first one, occurring at an early stage of the process, is characterized by a high friction coefficient (~1), typical of the strong adhesion of Cu–Cu contact. The second one is characterized by a lower steady-state friction (~0.7) related to the change of wear mechanism from adhesive metallic into triboxidative. By increasing the load the friction coefficient decreases, the transition time from the adhesive to triboxidative friction regime decreases and the contact temperature increases. Under abrasive wear conditions the penetration depth of the indenter is progressively reduced by increasing hardness, highlighting the benefits of MM and, even more, of MA. The Cu+0.5 wt.%TiB2 composite alloyed for 240 min shows the best wear resistance under both wear conditions. The good wear resistance combined to high thermal conductivity represent very attractive properties for many applications.