The effect of a boride diffusion layer on the tribological properties of AISI M2 steel

Abstract

AISI M2 high speed steel is commonly used as cutting tool in the machining process. Nevertheless, their useful life can be easily reduced by an eventual failure. In the last few years, thermochemical surface hardening process in which boron atoms diffuse into metals surface have been reported as an alternative to improve tribological properties. In the present work, a diffusional boron heat treatment was carried out at 950 °C by 6 h on AISI M2 steel sample. Scanning Electron Microscopy (SEM) and Micro-hardness testing was undertaken with the purpose to assess the diffusional boride microstructure and its effect on mechanical properties. On the other hand, tribological test was performed using a ball on disc tribometer tracking their friction coefficient and volume loss. Surface damage was analysed using stereomicroscopy and SEM. The boride diffusional layer achieved 50 µm with an increment of 7 times in the microhardness regarding to untreated sample and 4 times regarding to the adjacent zone to the boride layer. In addition, a reduction of the friction coefficient and better wear response was achieved as a result of boride heat treatment.