Effect of Severe Surface Plastic Deformation on Tribological Properties of CoCrWNi Super Alloys

The effect of severe surface plastic deformation on the microstructure and tribological properties of CoCrWNi super alloy L۶۰۵ was investigated. The surface of the annealed alloy was frictionally processed by a tungsten carbide tool with a tip radius of ۵ mm under different sliding speeds of ۵۰۰, ۸۰۰, ۱۱۰۰, ۱۴۰۰, ۱۷۰۰, and ۲۰۰۰ mm/min for ۲, ۵, ۱۰, ۲۰, and ۳۰ passes. Based on the results, applying friction hardening (FH) promoted the formation of the e-HCP (martensite) phase in the surface structure of the g-FCC alloy up to a depth of about ۵۰۰ mm. The maximum surface hardness was observed at the sliding speed of ۱۷۰۰ mm/min and ۳۰ passes, where the surface hardness increased by almost ۱۰۰% (from about ۳۲۰ HV to more than ۶۳۵ HV). Pin-on-disk wear tests were carried out at room temperature, under applied pressures of ۰.۲۵, ۰.۵, and ۱ MPa, for a sliding distance of ۱۰۰۰ m. According to the results, under low applied pressures, i.e. ۰.۲۵ MPa, the maximum wear resistance was observed in the sample FH-processed for ۳۰ passes at ۱۷۰۰ mm/min. However, due to the formation of lateral microcracks on the surface of samples processed by high number of FH passes, under the applied pressure of ۱ MPa, the lowest wear was observed in the ۵-pass processed sample (۱۷۰۰ mm/min). The wear rate and average friction coefficient (AFC) of this sample were about ۴۵% and ۳۰% lower than those of the base (annealed) sample, respectively.

کلیدواژه ها:

L۶۰۵ ، friction hardening ، hardness ، sliding wear ، tribology