Influence of Subsurface Micro/Nano-Structural Evolution on Macroscopic Tribological Behavior of Ni3Al Matrix Composites

Abstract

The relationship between macroscopic tribological behavior and subsurface micro/nano-structural evolution needs to be studied in detail. We report here the results of dry sliding tribological tests of Ni3Al matrix composites with 1.5 wt% graphene nanoplatelets (GNPs) under different loads. We found that the friction coefficient decreased with increasing load, while the wear rate showed a downward trend after an initial increase. During the sliding wear process, severe plastic deformation and an accumulation of friction heat caused the formation of an ultrafine layer (UL) and a matrix refinement layer (MRL). The UL contributes to the reduction of friction coefficient and wear rate, and the MRL contributes to the improvement of wear resistance. In addition, GNPs accumulating in the UL tend to be parallel to the worn surface, causing a reduction in friction and an increase in wear resistance for the properties of easily shearing off and high tensile strength. The hardness and elastic modulus of the UL and MRL increased due to grain refinement and the accumulation of GNPs in these layers. The effective hardness of the multilayer was approximately 7.2 GPa.