Microstructural and Tribological Characterization of Cryogenic Treated WC-Co Cutting Bits under Different Holding Times for Rock Cutting Applications

Cryogenic heat treatment is an advanced heat treatment process employed to modify the microstructure of a cutting bit to enhance its properties. This research study aims to investigate the effects of deep cryogenic treatment under different soaking times on the tribological performance of rock cutting bits. Cryogenic treatment was applied for 12-, 18-, 24-, 30-, and 36-h soaking duration, and their corresponding microstructural modifications were identified through SEM and XRD analysis. In accordance with the mechanical properties of deep cryogenic treated WC, the hardness initially strengthened up to 24 h (52.49%). Further increase in cryogenic treatment (36 h) leads to drop in hardness (CT 36: 32.46%). The microstructural observation confirms the conversion of martensitic phase from fcc to hcp-Co phase. The atomic percentage of Co was found to be higher (35.42%) for CT 24 bit as compared to UT bit. The variation in properties is due to the formation of ? carbides (Co3W3C, Co6W6C) and the martensitic transformation of a-Co to e-Co phase. Wear tests were conducted under dry condition using CT and UT bits. Multi-criteria decision-making optimization has been carried out through the grey fuzzy integrated Taguchi technique to obtain the optimized soaking duration along with load and speed. To predict the value of GFRG, an ANFIS model was developed, which resulted in 94.57% prediction accuracy. The treatment time influences 86.29% of the output responses. According to the results obtained, CT 24 bit exhibited best optimized results as compared to other bits, and hence, 24-h cryogenic holding time can be recommended for rock cutting applications.