Synergistic effects of cryogenic treatment and tempering on mechanical and microstructural properties of M42 HSS

High-speed steel (HSS) tools like M42 must perform well in precision machining applications that require hardness, stability, and wear resistance. The liquid nitrogen cryogenic treatment turns retained austenite into martensite and precipitates fine carbide. Hardness, wear resistance, and dimensional stability improve. Tempering reduces internal tension and toughness. Therefore, this work examined the synergistic effects of cryogenic treatment and tempering on M42 HSS to optimise its mechanical properties. The SEM and XRD analyses confirmed the effective transformation of retained austenite (RA) into martensite, resulting in a refined grain structure with reduced RA content. Cryogenic treatment promotes near-complete transformation of retained austenite into martensite, while subsequent tempering may cause partial reversion of austenite alongside carbide precipitation. The Vickers hardness test indicated that cryogenically treated materials had higher hardness values. The martensitic transition leads to the precipitation of carbide during the tempering process. Aerospace and automotive applications require these improvements because tool lifetime and performance affect operational efficiency and product quality. • Comprehensive analysis of M42 HSS subjected to a combination of cryogenic treatment and tempering. • Grain structure optimization achieved through martensite transformation and homogeneous carbide precipitation. • Hardness increased from 1214 HV to 1418 HV, indicating greater toughness and dimensional stability. • M42 HSS is well-suited for aerospace, automotive, and precision tools due to its increased wear resistance and endurance.