Study of Wear Stabilisation in Cryoprocessed Cobalt-Based High Speed Steel

Cryogenic treatment is employed for high speed tool steels in order to enhance their wear resistance. The improvement in wear resistance is associated with a decrease in retained austenite and or by formation of eta-carbide/nano-scale carbides. In the present work, a complex alloyed high speed tool steel (M35) specimens were hardened at 1,200 A degrees C, triple tempered at 400 A degrees C, cryosoaked at -185 A degrees C for 4-48 h and soft tempered (100 A degrees C). The microstructure of the samples were characterised for hardness, carbide density, impact energy, wear loss and residual stress. Influence of these measured parameters on wear behaviour was studied to understand underlying wear mechanism. The cryotreated specimens exhibited mild to stable wear transition at 16 h and then subsequent wear stabilisation for all higher cryosoaking intervals.