Microstructural refinement and enhanced mechanical properties of wire-arc additively manufactured Inconel 625 via a bottom cooling substrate system

This study investigated the microstructure evolution and performance characteristics of additive manufacturing Inconel 625 material via a bottom cooling substrate system. Compared with natural cooling, bottom cooling increased the average cooling rate from 5.15 °C/s to 7.87 °C/s. This significant rate increment directly regulated the molten pool's solidification process. The results show that bottom cooling increased the cooling rate by approximately 50 %, accelerating solidification. This acceleration refined MC carbides into finer, uniformly distributed particles and reduced Laves phase size. Additionally, bottom cooling decreased the average grain size from 192.17 μm to 184.74 μm and significantly lowered the maximum pole density in the selected sample area. The deposited structure primarily consists of columnar dendrites growing continuously through the layers, with equiaxed dendrites forming at the top. The texture strength significantly diminished, effectively mitigating the anisotropy of the material. The toughness of the material improved to some extent, evidenced by a typical ductile fracture morphology in tensile testing. Compared with the natural cooling sample, the microstructure of the bottom cooling sample exhibited greater uniformity. Furthermore, bottom cooling enhances the corrosion resistance of components, reduces the corrosion current density about 6 % and increases the impedance, while reducing porosity.