Heat treatments to improve microstructures of nickel alloys after selective laser melting

Abstract

Selective Laser Melting (SLM) is the preferred additive manufacturing process for manufacturing high-temperature metals such as nickel alloys, and it has revolutionized the ability to create complex, previously unimaginable structures. However, the full mechanical capabilities of alloys produced via SLM cannot be achieved without methods of controlling the microstructure and addressing defects. This work reviews combinations of hot isostatic pressing and other heat treatments that can reduce porosity, anisotropy, residual stress cracking, and undesired precipitate phases and enhance overall mechanical properties. Comparative studies of post-processing treatments are documented for the Inconel 718, Inconel 625, Inconel 738, Haynes 282, and Hastelloy X alloys. Although not all nickel alloys have been well characterized, post-processing methods have consistently shown the ability to achieve many microstructural properties equivalent to (and in some cases, better than) wrought samples. In addition, many recommendations apply to all nickel alloys, and the results of these existing studies can therefore help guide future research into post-processing procedures for newer alloys.