Abstract Scope |
Small variations in minor alloying element concentrations lead to remarkable differences in the grain structure, precipitate morphology, and tensile properties of Inconel® 625 fabricated by laser based directed energy deposition additive manufacturing. The secondary phases, which contribute to these different properties, originate from a complex interplay between the initial iron, silicon, and titanium contents of the powder feedstock. Relatively high amounts of silicon promote the formation of Laves phase, while high amounts of titanium favor MN-type nitrides. Ex-situ characterization revealed that the type, composition, and morphology of these precipitates evolve during hot isostatic pressing, although their total volume fraction remained virtually unchanged. The precipitate evolution was elucidated by in-situ high energy synchrotron x-ray diffraction measurements during a heat treatment replicating the thermal history of hot isostatic pressing. It is proposed that precipitate morphology can be controlled by careful selection of powder with appropriate amounts of minor alloying elements. |