Mechanisms of severe sliding abrasion of single phase steels at elevated temperatures: Influence of lattice structure and microstructural parameters

Abstract

Due to the complex influence of elevated temperatures on the characteristics of a tribological system, severe high temperature sliding abrasion of single phase metals is a unique type of wear. The mechanisms of high temperature sliding abrasion (indentation and grooving of metallic surfaces) are strongly governed by the temperature-dependent interaction between the bulk metal and the abrasive during the wear process. This interaction can be correlated with the metal physical and microstructural parameters of the worn metal, which consequently greatly influence abrasive wear processes.In this context, the present study deals with the influence of microstructural aspects of single phase steels on the mechanisms of high temperature abrasion. Investigations focus on the aspects of abrasion by performing high temperature hardness and sliding wear experiments (two-body, ceramic counter body) on bcc and fcc steels. Results confirm a clear lattice-structure dependence of the abrasion behavior of steels. Major differences exist in the stability of the mechanical and tribological properties of the bcc and fcc materials investigated. Hardness and work hardening of bcc steels decrease above 500°C, leading to non-stationary wear. In contrast, fcc steels show a steady decrease of mechanical properties, avoiding instabilities. Accordingly, wear experiments and investigations of the wear scars (surface and subsurface regions) show a higher wear resistance and more favorable mechanisms of high temperature abrasion of fcc steels (e.g. pronounced micro-ploughing). Further, the microstructural elements of fcc steels high temperature abrasion resistance are investigated in more detail using X-ray diffraction. Microstructural analysis using diffraction-line broadening (Rietveld analysis) is used to determine the degree of plastic deformation (microstrain) and the phase fraction of α′-martensite of the austenitic wear scars. These parameters are related to the present mechanisms of abrasion, explaining the high temperature wear properties of fcc steels.