Hot isostatic pressing temperature–driven microstructure–tribology relationships in laser powder bed fused pure chromium

Conventional processing of chromium has long been abandoned due to its high ductile-to-brittle transition temperature (DBTT), which promotes stress-induced cracking during solidification. Nevertheless, chromium and its alloys remain attractive for advanced applications because of their excellent high-temperature stability, oxidation resistance, and tribological performance. In this study, pure chromium was fabricated by laser powder bed fusion (LPBF) using optimized processing parameters, followed by hot isostatic pressing (HIP) at moderate and high temperatures to address LPBF-induced cracking and residual stresses. The influence of HIP temperature on microstructural evolution, mechanical properties, and tribological behavior was systematically investigated. HIP effectively improved densification and reduced internal defects; however, the HIP temperature strongly governed the balance between residual stress relief and grain growth. As-built LPBF chromium exhibited high hardness and wear resistance due to its fine grain structure and retained residual stresses. HIP at a moderate temperature was sufficient to relieve residual stress while preserving the fine microstructure, thereby maintaining favorable mechanical and tribological performance. In contrast, high-temperature HIP promoted pronounced <100> grain growth, which facilitated the formation of a stable oxide layer and enhanced lubricating effects during sliding, but at the expense of mechanical strength due to excessive grain coarsening. These results highlight the critical role of HIP temperature in tailoring microstructure–property relationships in additively manufactured pure chromium and suggest that oxide dispersion strengthening may be an effective strategy to suppress grain growth while leveraging the combined benefits of LPBF and HIP processing for refractory metals.