Tribochemical wear of cutting-tool ceramics in sliding contact against a nickel-base alloy

The wear behaviour of a SiAlON and a SiC whisker reinforced Al2O3 composite in dry sliding contact against Inconel 718 was investigated. For tribological characterization, the worn contact surfaces were analysed using tribometer data and calculation of wear volume in addition to SEM/EDX analysis. The surface contact temperatures were estimated by finite element simulations. The tribological behaviour is distinct for each ceramic. The wear in SiAlON undergoes an exponential decay with increasing frictional power due to the formation of lubricous tribolayers that separate both contacting surfaces; once the frictional power is high enough tribochemical wear dominates and delamination of the tribolayers takes place. The wear of Al2O3-SiC is lower than that of SiAlON especially at high frictional power, which can be mainly attributed to the chemical stability of the alumina matrix and the formation of stable lubricous tribolayers. FEM simulations indicated high contact temperatures with steep gradients in the depth.