Tribological and mechanical properties of deep cryogenically treated medium carbon micro alloy steel

In this study, the effects of deep cryogenic treatment (sub-zero treatments at -196 °C) on the microstructural, mechanical, and tribological behaviours of commercial Vanadium-Titanium micro-alloyed 38MnVS6+Ti steel was investigated. The samples were quenched (conventionally heat treated), deep cryogenically treated and then tempered at 250 °C for 1 h. Deep cryogenic treatments were applied for three different soaking times (namely 8 h, 12 h, and 24 h). The effects of deep cryogenic treatment on the specimens were evaluated in terms of impact toughness, hardness, wear resistance, and microstructure. The results indicated that the application of longer deep cryogenic treatment times significantly improved wear resistance, and improved the hardness slightly (1 to 3 HRC). However, deep cryogenic treatment also reduced the impact toughness compared to that of the conventionally heat treated sample, due to the precipitation of carbides and increasing hardness.