Investigation on subsurface layer of Ni3Al-alloy and its composites induced by friction

Paper in proceeding, 2012

Evaluation of the wear behaviour of a Ni3Al-based (NAC) alloy and its composites by pin-on-disk (POD) testing indicates that the wear mechanism of the materials varied from that of traditional multi-phase cast irons. It was recognised that the wear of a Ni3A-based alloy and its composites was mainly caused by their plastic deformation and resulted in the formation of a specific subsurface layer at the worn surface. Nanoindentation and numerical regression analysis were further applied to study the friction induced on the subsurface layer of the alloy and its composites. Fitting functions and relevant curves of nanohardness of the Ni3Al matrix versus the surface distance from the worn surface, compressive deformation strain of the monolithic Ni3Al-based alloy versus nanohardness, and the friction-induced strain of the monolithic Ni3Al-based alloy versus surface distance were determined. It was determined that gradually distributed plastic strain with various microstructures was induced in the subsurface layer by friction. The addition of hard Cr3C2 particles reduced the thickness of the subsurface layer and retained the same peak hardness of the friction surface as the monolithic Ni3Al-alloy, which indicates a 50% wear rate reduction on both sides of the pin and disk. The use of MnS particles as a solid lubricant was studied in a NAC-alloy/MnS composite. An ineffective strain-hardening effect on the friction surface of the composite led to a less protected surface layer and an unimproved specific wear rate, though a low wear rate on its counterpart disk and a low friction coefficient of the friction pair were obtained. Finally, a kinetic and periodic process was proposed and used to understand the wear mechanism of the studied Ni3Al-based materials.