Precipitation and dissolution of δ and γ during heat treatment of a laser powder-bed fusion produced Ni-based superalloy

One drawback of the laser powder-bed fusion additive manufacturing (AM) technique is the build-up of residual stresses during processing that requires a stress-relief heat treatment prior to components being removed from the build plate. Here, we demonstrate the coprecipitation of the gamma ''-phase alongside the known delta-phase, during stress-relief annealing of AM Inconel 625 at 870 degrees C. The unexpected precipitation of gamma '' in the AM material is attributed to the local solute enrichment to the interdendritic regions of the as-built solidification microstructure. Dissolution of the delta and gamma '' phases is achieved after annealing for 15 min at 1150 degrees C. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.