Hydrogen uptake of 100Cr6 bearing steel in gaseous pressurized hydrogen and resulting tensile strength

Samples of martensitic-hardened bearing steel 100Cr6 (AISI 52100) were exposed to hydrogen atmospheres at different gas pressures. The resulting hydrogen contents were measured, and a pressure-dependent hydrogen charging curve was established. Tensile tests on cylindrical specimens charged at various hydrogen pressures showed a pronounced reduction in strength at hydrogen contents as low as 0.75 × 10$^{–6}$. Fractographic analysis revealed predominantly intergranular fracture with crack propagation along carbide-featured grain boundaries, indicating hydrogen enrichment at microstructural traps. Specimens, in which diffusible hydrogen was allowed to outgas prior to testing, largely recovered their initial strength, demonstrating that the observed embrittlement is mainly governed by diffusible hydrogen and is, to a significant extent, reversible. These findings provide insight into the pressure-dependent influence of hydrogen on the strength and reliability of bearing components operating in hydrogen environments.