Influence of post-sintering sizing process on the tribological behaviour of self-lubricating iron-based composite

Abstract

This paper aims to investigate the effect of post-sintering sizing process on the tribological performance of self-lubricating iron-based composites. Hollow cylindrical specimens were produced by powder metallurgy. Sizing was performed by repressing the as-sintered specimens in a hydraulic press die at three different pressures: 160, 320, and 480 MPa. The tribological characterization was carried out by reciprocating dry sliding tests using a ball-on-cylinder configuration. Variable load tests were performed to evaluate the scuffing resistance, whereas constant load tests were used to assess the wear rate and friction coefficient of the composites. The results show a gradual sealing effect of porosity and lubricants reservoirs and the hardening of the surface metallic matrix (up to 98%). The scuffing resistance was reduced by 72% at higher sizing pressures due to the lower availability of solid lubricants on the surface to maintain the tribolayer. The improved surface finishing and metallic matrix hardness reduced up to 70% of the tribosystem's wear rate at 320 MPa of sizing pressure. Furthermore, a detrimental effect on the wear resistance was noticed for the specimen sized at a higher sizing pressure (480 MPa), showing the importance of optimizing the sizing pressure to improve the tribological behaviour of sintered self-lubricating composites.