Mechanical properties and microstructure evaluation of powder bed fused Inconel 625 Nickel Alloy

This research focused on comparing laser fused Inconel 625 by the method of Powder Bed Fusion (PBF) with conventionally wrought Inconel 625. Property comparisons were made in the as-deposited PBF condition and after heat treatments typically used for wrought Inconel 625. Stress relief and solution anneal heat treatments used to promote solid solution strengthening and precipitation hardening were employed for the as-processes PBF and wrought samples. The distribution, size and morphology of the precipitates of Inconel 625 produced by PBF were compared with wrought material to determine differences in mechanical properties. Mechanical properties were determined by tensile testing, micro hardness measurements and metallographic observations. Powder bed fused samples in the non-heat treated and heat treated forms tested higher in ultimate tensile strength, 0.2% yield strength, elongation and Vickers hardness, when compared to the cast and wrought samples. The dendrite arm spacing and grain size for the additive manufactured samples was smaller than the cast and wrought samples. Microstructure analysis showed the formation of carbides as well as nitrides during heat treatment that were similar to samples produced in a non PBF method. The PBF samples displayed higher cooling rates which attributed to the smaller grain size and the smaller dendrite arm spacing than the cast-wrought samples. The PBF produced samples that were overall a stronger sample (UTS, YS and Vickers hardness) than the cast-wrought samples.