Post-processing Optimization of Laser Powder-bed Produced Inconel 625 for Improved Mechanical and Corrosion Properties

Inconel 625 (IN625) has found widespread use in many industries because of its combination of high strength and corrosion/oxidation resistance over a wide range of temperatures and harsh environmental conditions. Its excellent weldability has also made it a popular material for additive manufacturing (AM) applications. However, the often unpredictable properties of AM-produced materials hinder the application of AM IN625 and other alloys in components for commercial applications. Most AM studies, including those on IN625, focus on laser/powder interactions, scan strategy, and other processing considerations, and their effect on mechanical behavior. Very little work emphasizes the development of appropriate post-build heat treatments necessary to relieve residual stress and produce uniform, consistent microstructure and properties. The dynamic, locally varying processing conditions of AM techniques result in heterogeneous microstructures that look nothing like their wrought counterparts. These inhomogeneities promote variability in the mechanical performance, and are likely to influence the corrosion resistance as well. Understanding the influence of microstructure on properties of is essential for reliable predication of in service behavior of AM IN625 components; and control of microstructure through post-build thermal processing is the key. This presentation describes a series of experiments designed to evaluate the influence of the AM microstructure on the mechanical and electrochemical performance of IN625, and to optimize the post-build heat treatment procedure for maximum material performance. The experimental designs, and the results of microstructural studies for AM materials will be compared to the performance of wrought IN625, and discussed.