Microstructural evolution of heat-treated Cr–W–V–Mo steels: effect of core-shell carbides and secondary precipitation on their abrasion resistance

This study aims at understanding the effect of different heat treatments on the evolution of the microstructure of several Cr–W–V–Mo steels having different compositions and how this latter affects their abrasion resistance. The investigation also gives insights on the formation and effect of core-shell carbides on the abrasion resistance. The commercial highly alloyed stainless steel HCx® and six newly designed Cr–W–V–Mo steels were subjected to three heat treatments: austenitizing at 900 °C and 1100 °C and subsequent quenching, and an ageing treatment at 700 °C. The microstructural analysis demonstrated the formation of Laves phase when austenitizing at 900 °C; this phase is depleting the matrix from carbide forming elements without any improvement in the wear behavior of the alloys. However, increasing the austenitization temperature to 1100 °C favored the development of core-shell carbides that contribute to increase the abrasion resistance of the alloys. The ageing treatment promoted the precipitation of secondary carbides uniformly distributed along the matrix, and they were found to have a beneficial effect on maintaining the good abrasion resistance even after subjecting the steels to a high ageing temperature (700 °C) for long duration (10 h).