The microstructure and oxidation resistance of Laser Beam Melted (LBM) and Conventionally Manufactured (CM) Inconel 625 alloys were studied at 900 °C and 1050 °C. The microstructure of the LBM samples was cellular, with Nb and Mo segregations located at the cell walls. At 900 °C, the oxidation rate was similar for both materials but was clearly higher for the LBM material at 1050 °C. This high oxidation rate induced poor oxide scale compactness, void formation in the subsurface region and the formation of a high amount of Nb 1.

Metal dusting resistance of Inconel 625 alloy obtained by laser beam melting (LBM), compared to wrought alloy 625 was assessed during 9 500 h at 610°C. Whatever the manufacturing process, the mass variations were very small when the systems were ground thanks to the formation of a uniform protective chromia layer. However, the high surface roughness was shown to be detrimental as the waviness favoured the local formation of an unprotective spinel oxide. Hot isostatic pressure (HIP) treatment recrystallized the alloy and increased its grain size. This reduced chromium diffusion towards the surface, explaining the poorer resistance of the LBM + HIP system.