The influence of post-thermal treatment on the structure and impact toughness of bulk parts made from heat-resistant steel produced by wire arc additive manufacturing technology

This study examines the effect of heat treatment on the microstructure and impact toughness of steel components produced through Gas Metal Arc Welding (GMAW), employing both standard and coldArc modes. Wire Arc Additive Manufacturing (WAAM) was utilized to fabricate multilayer structures using OK Autrod 13.14 wire on a 12Cr1MoV heat-resistant steel substrate. The research explores the challenges associated with optimizing thermal effects during the additive manufacturing process to improve mechanical performance while ensuring geometric accuracy. The results reveal that the primary microstructure of the printed walls consists of bainite with layers of allotriomorphic ferrite. Thermal accumulation during the deposition process diminishes cooling rates, resulting in a reduction of microhardness in the central sections of the wall. The coldArc mode, which is distinguished by reduced heat input, promotes the formation of a finer microstructure, thereby achieving superior strength and microhardness compared to the standard GMAW process. Heat treatment enhances diffusion processes, increases ferrite phase content, and refines grain morphology. The finer initial microstructure of the coldArc mode limits grain growth during heat treatment, preserving strength characteristics. While printed walls exhibit high tensile strength (up to 680 MPa) but limited ductility, heat treatment improves plasticity by increasing ferrite content and relieving internal stresses. Nonetheless, deformation localization associated with the layered structure persists. The findings indicate that the integration of optimized WAAM process parameters with post-printing heat treatment can significantly enhance mechanical properties, thereby expanding the potential applications of additive manufacturing for critical components fabricated from heat-resistant steels.