Potential of nitrogen atomized alloy 625 in the powder bed fusion laser beam process

Abstract

Powder based metal additive manufacturing processes like Powder Bed Fusion – Laser Beam utilize gas atomized metal powders as feedstock material. Typically, for nickel-based alloys such as Alloy 625, argon gas is used during the atomization process. Considering the larger environmental impact of argon gas compared to nitrogen gas, and the increasing use of gas atomized metal powders, the environmental impact of powder based additive manufacturing techniques could be mitigated if gas atomization of alloys such as Alloy 625 using nitrogen was possible. This work investigates the feasibility of tailoring an alloy to allow atomization using nitrogen gas while remaining within the Alloy 625 specification. This is achieved by limiting the nitrogen pick-up during the atomization process, primarily by reducing the titanium content. The metallurgical implications of this tailored alloy and the subsequent atomization using nitrogen, as well as the attained microstructure from the Powder Bed Fusion – Laser Beam process is investigated and compared to a more common 625 alloy composition which was atomized using argon. Furthermore, the microstructural development of the alloys after heat treatments are evaluated. Lastly corrosive properties, as well as tensile and impact properties are evaluated both in the as-built and hot isostatic pressed condition.