Worn surface and subsurface layer structure formation behavior on wear mechanism of CoCrFeMnNi high entropy alloy in different sliding conditions

Abstract

In this study, equiatomic CoCrFeMnNi high entropy alloy (HEA) was fabricated by induction melting and subsequent thermomechanical treatments were carried out to achieve single FCC phase with equiaxed grains. The friction and wear behavior of HEA was investigated using ball-on-disc configuration in dry and ambient conditions under different sliding time, normal load and velocity. The detailed microscopic characterizations were invested to examine the worn surface and subsurface deformation mechanisms to identify the kinds of wear involved during dry sliding process. Results revealed the hardness of deformed layer showed 63% higher than matrix owing to grain refinement induced by sliding friction. The friction coefficient stabilized at longer sliding time due to oxidized wear debris acting as as lubricant behavior during sliding. While wear rate significantly decreased with increasing sliding time due to oxidation of wear debris on worn surface and formation of deformed layer with grain refinement resists the plastic deformation by strengthening the subsurface layers. On the other hand, wear rate stabilized for 6 and 8 N due to worn surface oxidation and subsurface hardening. Moreover, wear rate stabilized at higher sliding velocity owing to balance between subsurface hardening and delamination behavior.