Microstructural evolution and surface property enhancement of H13 tool steel via TIG-based surface alloying under...

Surface melting and alloying of H13 tool steel were investigated using the tungsten inert gas (TIG) process under argon and argon-nitrogen shielding atmospheres. The influence of key process parameters, including current intensity and shielding gas composition, on the characteristics of the modified surface was systematically examined. The dimensions of the treated zones, microstructural features, and hardness profiles were found to be strongly dependent on the applied parameters. In addition, a subset of the surface-treated specimens underwent austenitizing, quenching, and tempering according to standard heat treatment procedures for H13 steel. Microstructural characterization using optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) revealed that defect-free and homogeneous melt zones were formed. The solidified microstructures were predominantly martensitic, accompanied by finely dispersed carbide and nitride precipitates. A maximum surface hardness of approximately 800 HV, corresponding to nearly four times that of the untreated substrate, was achieved in samples processed under an argon-nitrogen atmosphere followed by post-treatment tempering. The significant hardening effect is attributed to martensitic transformation and the formation of finely distributed carbide and nitride phases within the melted zone. These surface characteristics indicate potential relevance for high-durability biomedical tooling applications, particularly for reusable and indirectly used medical instruments, while acknowledging that further validation is required for clinical translation.