Defect formation and its mitigation in selective laser melting of high γ′ Ni-base superalloys

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Colleges, School and Institutes

Abstract

This report focuses on the microstructural causes of cracking in CM247LC processed using Selective Laser Melting (SLM), as well as other phenomena that may increase the likelihood for cracking. Observations using high-speed imaging showed that material was lost as both vapor and discrete particles under some conditions, which may be a source of the Al-enriched particles found in recycled powder. The local chemical heterogeneities arising from such Al-rich particles may then contribute to crack and pore formation. Transmission Electron Microscopy (TEM) investigations for the as-built microstructure showed "cell-like" structures within the columnar grains, Hf-rich precipitates were found at "cell-like" structures and grain boundaries, and there were associated high dislocation densities at these boundaries acting as crack initiation points in the presence of residual stresses. Post-process Hot Isostatic Pressing (HIP) was used to heal the cracks and pores that form during processing. It was found to lead to pronounced recrystallization, as expected from the high dislocation density. Various routes for defect mitigation are discussed.

Details

Original languageEnglish
Title of host publicationSUPERALLOYS 2016 - Proceedings of the 13th International Symposium on Superalloys
Publication statusPublished - 28 Oct 2016
Event13th International Symposium on Superalloys, SUPERALLOYS 2016 - Seven Springs, United States
Duration: 11 Sep 201615 Sep 2016

Conference

Conference13th International Symposium on Superalloys, SUPERALLOYS 2016
CountryUnited States
CitySeven Springs
Period11/09/1615/09/16

Keywords

  • CM247LC, Cracks, Precipitates, Selective laser melting, Texture