Microstructural changes in a laser solid forming Inconel 718 superalloy thin wall in the deposition direction

The microstructure variation of as-deposited Inconel 718 superalloy sample in deposition direction fabricated by laser solid forming (LSF) was investigated. It was found that the as-deposited microstructure was mainly consisted of predominant gamma columnar dendrites directionally growing along the deposition direction. Primary dendrite arm space measurement revealed spaces of 11.5, 17.5 and 38.0 mu m at the bottom, the middle and the top section of the LSF sample respectively. The result was further studied by comparing with the Kurz-Giovanola-Trivedi (KGT) dendrite growth model, which was in a reasonable agreement with the experimental result. The various microstructures and micro-segregation situations at different sections of the LSF sample, which were induced by the thermal accumulation during LSF process, were also carefully discussed. (C) 2012 Elsevier Ltd. All rights reserved.