Evaluation of factors influencing deep cryogenic treatment that affect the properties of tool steels

Deep cryogenic treatment (DCT) of tool steels is used as an additive process to conventional heat treatment and usually involves cooling the material to liquid nitrogen temperature (−196 °C). This kind of treatment has been reported to improve the wear resistance of tools. In this study, the Taguchi method was used to identify the main factors of DCT that influence the mechanical properties and the wear resistance of the powder metallurgically produced cold-work tool steel X153CrVMo12 (AISI D2). Factors investigated were the austenitizing temperature, cooling rate, holding time, heating rate, and tempering temperature. In order to study the significance of these factors and the effect of possible two-factor interactions L₂₇(3¹³), an orthogonal array (OA) was applied to conduct several heat treatments, including a single DCT cycle directly after quenching prior to tempering. The results show that the most significant factors influencing the properties of tool steels are the austenitizing and tempering temperatures. In contrast, the parameters of deep cryogenic treatment exhibit a lower level of significance. Further investigations identified a nearly constant wear rate for holding times of up to 24 h. The wear rate reaches a minimum for a longer holding time of 36 h and increases again with further holding.