Optimization of cryogenic treatment to improve the tribological behavior of Vanadis 6 steel using the Taguchi and grey relation approach

In this work, Vanadis 6 cold work ledeburitic tool steel was cryogenically treated at different temperatures, and then low- or high-temperature tempered. The current research focused on the effect of process variables on the calculated wear rate, counterpart's material transfer, and friction coefficient. Results of pin-on-disk wear tests were evaluated using a Taguchi L18 orthogonal array with varying cryogenic temperatures (−75 °C, −140 °C, and −196 °C), tempering temperatures (170 °C and 530 °C), sliding velocity (0.064 m/s, 0.128 m/s, and 0.1885 m/s), and loads (1, 5, and 10 N) as parameters. Analysis of variance (ANOVA) was used to analyze the statistical significance and contributions of process factors to wear behavior. Confirmation tests were performed to verify the model accuracy, and the results show error values below 10%. The experimental works revealed that the wear rate increases with increasing load, but the friction coefficient is also strongly affected by the sliding speed. The dominant wear mechanism is adhesive with significant oxidation, abrasion, and delamination of adhered counterpart's material. To maximize the wear performance, it is necessary to process the steel at −140 °C with subsequent tempering at 170 °C.