Microstructural study of the nano-scale martensitic lamellar α-Co and ε-Co phases of a Co–Cr alloy fabricated by selective laser melting
Hyung Giun Kim, Won Rae Kim, Hyun Woong Park, Gyung Bae Bang, Kyung‐Hwan Jung, Yong Son, Sung Hwan Lim
Abstract
An interfacial microstructural study was carried out to clarify the hardening mechanism of an as-built Co–Cr alloy fabricated by selective laser melting (SLM). Using transmission electron microscopy, we found a unique martensitic lamellar microstructure with a specific orientation relationship between the α-Co and ε-Co phases; specifically, a nanoscale microstructure consisting of (111)α-Co//(0002¯)ε-Co and [01¯1]α-Co//[1¯21¯0]ε-Co was formed on the Co–Cr alloy. The Co–Cr alloy fabricated by SLM with a martensitic microstructure achieved a Vickers hardness value of approximately 369.36 ± 11.86 HV without any secondary-phase particles such as carbides.