Carbide precipitation characteristics in additive manufacturing of Co-Cr-Mo alloy via selective electron beam melting

Carbide precipitation plays a key role in determining mechanical properties of Co-Cr-Mo alloy. Precipitation characteristics of carbides in selective electron beam melting (SEBM)-fabricated Co-Cr-Mo parts have been investigated by atom probe tomography and transmission electron microscopy. We observe co-existence of two types of carbides, i.e. M23C6 and M6C, which are formed into continuous carbide thin films along columnar grain boundaries. The carbide thin film is found to precipitate coherently with one gamma-Co grain while incoherently with another adjacent one. Moreover, columnar carbide chains or clusters consisting of nanometer-sized, cuboidal particles are precipitated coherently with surrounding gamma-Co phase within interdendritic regions. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.