Microstructural evolution and mechanical properties of selective laser melted a nickel-based superalloy after post treatment

Although additive manufacturing (AM) has developed significantly due to its numerous process advantages, some adverse effects include large columnar grains and detrimental tensile residual stress, which can weaken the performance of the final part. In this study, a new post-treatment method combining heat treatment and laser shock peening was employed to alter the microstructure and mechanical properties of AM-processed Inconel 625 alloy (IN625). The microstructural evolution of IN625 after different treatments was studied. Results showed that many gamma' precipitates were formed after heat treatment. After heat treatment followed by laser shock peening treatment, gradient microstructure along depth direction was generated. High-density dislocation structures and refined grains were produced in the subsurface layer after heat treatment followed by laser shock peening treatment. Moreover, the precipitates interacted with dislocations. High levels of compressive residual stress could be generated after heat treatment followed by laser shock peening treatment, resulting in high ultimate tensile strength and large elongation. This combined heat treatment and laser shock peening method is helpful in enhancing the mechanical performance of AM parts through changing their microstructure and residual stress distribution.