Abstract
Cold‑work tool steels are widely employed in dies, cutting tools, and wear‑intensive applications where achieving an optimal balance between hardness and toughness is critical. This balance remains a challenge, particularly when cryogenic treatments are employed to minimize retained austenite and enhance dimensional stability. The present study addresses this challenge through a systematic investigation of the hardness–toughness relationship in AISI D2 tool steel, a high‑carbon, high‑chromium alloy selected for its industrial relevance and strong secondary hardening response.
The research investigates the combined effects of conventional quench-and-temper processing, deep cryogenic treatment (DCT), and cyclic deep cryogenic treatment (CDCT) response of D2 steel. Each treatment condition was further paired with single, double, and staged tempering cycles. The mechanical performance was evaluated using Rockwell hardness, KIC fracture toughness, and reciprocating tribometry for wear evaluation. The structure-property relationships were established through phase quantification by X‑ray diffraction, microstructural characterization using SEM/EDS and EBSD, and post-test wear track analysis to identify dominant wear mechanisms.
Although the mechanical behavior of cold-work tool steels such as D2 and high-carbon, high-vanadium grades has been studied extensively in relation to cryogenic processing, no systematic investigation has yet clarified the hardness-toughness trade-off required for optimized performance. This study is designed to provide evidence‑based guidelines for heat treatment of D2 steel, with the aim of elucidating the influence of cryogenic processing on secondary hardening behavior. It also identifies tempering strategies that recover toughness while maintaining high hardness and offering practical insights for industrial die and tooling applications where both wear resistance and impact tolerance are critical.