Inconel 625 and stainless steel 316L dual wire arc additive manufacturing of functionally graded materials

Abstract

Wire Arc Additive Manufacturing (WAAM) is a layer-by-layer manufacturing technology that has evolved into a potential solution for manufacturing large-scale metallic components with low and moderate structural complexity. This dissertation aims to narrowing the research to fabricate the Functionally Graded Materials (FGMs) of varying combinations of Stainless steel (SS316L) and Nickel-based (IN625) superalloy using WAAM. For the purpose, the Gas Tungsten Arc Welding (GTAW) was used as heat source, and the SS316L and IN625 wires were feed into the stabilized arc of GTAW. The wires were fed using the cold wire feeder and deposited layer by layer on the steel substrate. Functionally graded materials of SS316L and IN625 have an application in nuclear power plants, oil and gas industries (like marine risers), automotive industries, and where high-temperature strength and corrosion-resistant material are required. The process parameters were optimised to obtain the possible combination of weight percentage for both the materials. Sandwich and incremental gradient structure of various patterns were successfully fabricated. The deposited parts were observed to be free from defects such as microcracks and voids as confirmed by microstructure analysis. EDS scan and micro-indentation hardness were also analysed to investigated the gradient variation and mechanical properties. EDS line scan for the 10% incremental gradient samples showed the stair change, whereas the sandwich gradient wall shows alternate crest for the key element Ni and Fe. Keywords: Wire Arc Additive Manufacturing, Stainless Steel, Nickel-based superalloy, Gas tungsten arc welding.