Residual Stresses in Inconel 718 Parts Fabricated with Different Additive Manufacturing Methods

There is strong interest in additively manufacturing (AM) Ni-super alloys for high-temperature applications in the aerospace industry. Multiple methods of AM have been developed over the past decade to cater to specific metal alloy development and desired material properties. Depending on the method used, variations in microstructure, mechanical properties and residual stresses can result using a similar alloy starting powder.  For example, Inconel 718 builds fabricated by selective laser melting and electron beam melting result in a difference of in inter-granular spacing. In addition, significantly different residual stresses trends are seen between laser and electron beam melting processes. Each AM method produces a unique thermal “finger print” which drives the differences seen in microstructure and residual stress. Modeling and validation of these thermal processes is therefore essential for ensuring quality control in end products.  In this presentation, comparisons of experimentally determined residual stress, microstructure, and modeling will be discussed relative to Inconel 718 fabricated by different methods of additive manufacturing.