Effect of prior austempering heat treatment on the microstructure, mechanical properties and high-stress abrasive wear behaviour of a 0·33% C dual-phase steel

Abstract

The present study investigates the effect of prior austempering heat treatment on the microstructure, mechanical property and high-stress abrasive wear response of 0·33% carbon dual-phase (DP) steel. DP steels were produced by intercritical annealing of the as-received steel (DP-AR) and of the steel subjected to prior austempering heat treatment (DP-AT). Prior austempering heat treatment results in the refinement of martensite phase in DP-AT steel, which is responsible for generation of less strain and microcracks in the vicinity of martensite phases. Therefore, this steel exhibits improvement in ductility with a marginal loss in strength. On the other hand, DP-AR steel shows coarse martensite phase which promotes strain accumulation and thereby generation of microcracks. These microcracks are found to be responsible for poor ductility in this steel. Furthermore, abrasion tests were carried out at varying sliding distances at 7 N applied load. DP treatments result in improved overall wear response. However, prior austempering heat treatment results in improvement in wear resistance in DP-AT steel at all sliding distances except at initial period. This is attributed to finer morphology of martensite and the absence of microcracks along with higher strain hardening in DP-AT steel. However, the improved wear resistance at initial period of DP-AR steel is attributed to considerably higher strain hardening index at low strain as compared to DP-AT steel.