Selective laser melting additive manufacturing of Inconel 718 superalloy parts: Densification, microstructure and properties

This paper presented a comprehensive study of densification behavior, microstructural features, microhardness, wear performance and high-temperature oxidation properties of Inconel 718 parts fabricated by selective laser melting (SLM), a typical additive manufacturing process. The relationship of processing conditions, microstructures and material properties was established. The occurrence of balling phenomenon at a lower laser energy density input reduced the relative density of the formed parts. A reasonable increase in laser energy density yielded a near-full densification. The typical microstructures of SLM-processed Inconel 718 parts experienced successive morphological changes on increasing the applied laser energy density: coarsened columnar dendrites - clustered dendrites - slender and uniformly distributed columnar dendrites. The optimally prepared fully dense Inconel 718 parts had a uniform microhardness distribution with a mean value of 395.8 HV0.2, a considerably low friction coefficient of 0.36 and a reduced wear rate of 4.64 x 10(-4) mm(3)/N m in sliding wear tests. The formation of an adherent tribolayer on the worn surface contributed to the improvement of wear performance. The high-temperature oxidation resistance was enhanced as the applied laser energy density increased and the elevated high-temperature oxidation property was primarily attributed to the formation of refined microstructural architectures of SLM-processed parts. (C) 2013 Elsevier B. V. All rights reserved.