Enhancing wear resistance of tool steel materials for industrial automobile component using cryogenic treatment

The durability of sheet metal punching tools depends largely on their wear resistance and frictional behaviour during service. Deep cryogenic treatment (DCT) has emerged as an effective post-heat-treatment process for improving the tribological performance of tool steels. This study experimentally investigates the influence of DCT on the wear characteristics and service life of three commercially used tool steels, namely EN31, AISI D2, and OHNS, employed for punching and piercing 4.5 mm thick SAPH440 sheet steel. The tool steels were conventionally heat treated, deep cryogenically treated at − 196 °C for 18 h and subsequently tempered. Their tribological behaviour was evaluated using a pin-on-disc wear test under dry sliding conditions at a load of 140 N. Wear, wear resistance, wear coefficient, frictional force, and coefficient of friction were determined for each material. The tribological performance of EN31, D2, and OHNS tool steels improved significantly after conventional heat treatment with tempering (CHTWT) and deep cryogenic treatment with tempering (DCTWT) compared with the raw condition. The average wear decreased by 91% for EN31, 86.5% for D2, and 87% for OHNS after conventional heat treatment. Following deep cryogenic treatment, the wear reduction further increased to 94% for EN31, 98% for D2, and 93% for OHNS compared with the untreated specimens. DCT followed by tempering improved the tribological performance of all the investigated tool steels. Among them, AISI D2 exhibited the best overall performance, with the lowest average wear (26 μm), highest wear resistance (4.67), lowest wear coefficient (2.91 × 10 −5 ), lowest average frictional force (14 N), and lowest coefficient of friction (0.10). Compared with the conventionally heat-treated condition, the wear resistance of D2 increased by 517%, while the average wear decreased by 85%. SEM analysis was performed to examine the worn surfaces, while industrial punching trials were conducted to assess tool life under actual operating conditions. SEM observations revealed shallow wear grooves and a homogeneous martensitic matrix with finely dispersed carbide particles, consistent with the improved wear behaviour. Industrial punch life was highest for D2 (3765 min), followed by EN31 (3130 min) and OHNS (2665 min). The results demonstrate that DCT followed by tempering is an effective post-heat-treatment process for enhancing the tribological performance and service life of industrial tool steels, with AISI D2 providing the best overall performance for SAPH440 sheet metal punching applications.