Instability in wear mechanism and its relevance to microstructural features in cryotreated T42

Abstract

This paper investigates effect of microstructural changes in AISI T42 that occurred due to cryogenic treatment on the material properties such as wear behaviour, hardness and impact energy. Specimens of T42 were hardened in the salt bath at 1215°C, tempered four times in salt bath at 550°C followed by air cooling. All specimens were cryotreated at −185°C for varying length of cryosoaking periods followed by soft tempering at 100°C. Samples characterised for residual stress, carbide density, hardness, impact energy and wear volume. An optimum cryosoaking period of 8 h was established with appreciable combination of carbide density, hardness and dramatic reduction in wear rate by 58%. Morphology of carbides and merging of ultramicroscopic W rich and V rich carbides at higher cryosoaking period on material properties was analysed. Microstructural changes at subsurface has been correlated in light of prevailing the wear mechanism and operative wear modes.