Effects of Heat Treatment on Direct Laser Fabricated Stainless Steel 420-Inconel 718 Alloy Multi-material Structures

Everyday consumer products consist of multi-material structures (MMS) due to being aesthetically appealing and multi-functional. Additive manufacturing techniques such as laser directed energy deposition (laser DED) can fabricate multi-material structures (MMS) in a near single step. Many components fabricated via laser DED require post-processing operations such as heat treatment and this is challenging for MMS. In this study, laser DED fabrication and heat treatment of stainless steel 420 (SS420) and Inconel 718 (IN718) MMS are investigated. Different compositions of SS420 and IN718 alloys for the multi-material regions were investigated and performance were found to be weaker than the parent materials. The present study improved this multi-material regions' performance by devising a specialized heat treatment for the SS420 and IN718 multi-material structures. Five different coupons (by weight): 100% SS420, 75% SS420 + 25% IN718, 50% SS420 + 50% IN718, 25% SS420 + 75% IN718, and 100% IN718 were fabricated using laser-DED process. The mechanical performance was correlated to the microstructural features, before and after heat treatment, using destructive and non-destructive techniques. The result was a novel SS420 + IN718 mixture chemistry that had properties comparable to the parent alloys, thus eliminating a weak link in the MMS.