Correlation between residual stresses and the tribological behaviour of Inconel 625 coatings

Abstract

Residual stresses in thermal spray coatings are amongst the major limiting factors in achieving maximum performance of these coatings in both corrosive and high wear service environments. Moreover, due to the complexity of their origin and distribution in coatings there is a lot of variability in studies aimed at understanding their nature and influence on performance of thermal spray coatings. The aim of the research work was therefore to investigate the effect of residual stresses on the tribological behaviour of high velocity oxy-fuel sprayed Inconel 625 coatings. In order to achieve different stress states, coatings were deposited at different thicknesses of 250 μm, 300 μm, 400 μm and 500 μm. The sin2ψ method was then used to determine the evolved surface residual stresses in the coatings. Sliding wear tests were carried out at three loads of 70 N, 110 N and 150 N in order to study the influence of the residual stresses on the frictional and wear behaviour of the coatings under different loading conditions. The coefficient of friction was observed to decrease with increasing sliding load for all the Inconel 625 coatings of different thicknesses. A positive correlation was established between the residual stress state of the coatings and their wear volumes at the different loading conditions.