Microstructure and retained austenite in Ni–W–Cr forged steel: Characterization of W/Cr-rich carbides and phase distribution

The development of high-strength structural steels with superior thermal stability remains a critical challenge in advanced engineering applications. This study provides a comprehensive evaluation of the processing–microstructure–property relationships in a multipass-forged Ni–W–Cr alloy steel subjected to controlled thermomechanical treatment. Forging was conducted at 900–1150 °C under strain rates of 0.1–10 s −1 , followed by austenitization at 850 °C, water quenching, and tempering at 600 °C for 2 h. Detailed characterization using SEM, EBSD, XRD, and EDS revealed the formation of an ultrafine lath martensitic matrix (2–5 μm block size) with uniformly distributed W- and Cr-rich carbides (M 6 C and M 23 C 6 ). Retained austenite was observed at lath and packet boundaries in the hot-forged condition, whereas quench-and-temper treatment reduced the γ-phase content, resulting in a predominantly martensitic structure. The optimized microstructure achieved a yield strength of ∼1000 MPa, ultimate tensile strength of ∼1200 MPa, and hardness of ∼520 HV, while maintaining tensile stability at 600 °C. These findings provide an effective framework for designing high-performance Ni–W–Cr steels for demanding structural applications.