Selective laser melting of the hard-to-weld IN738LC superalloy: Efforts to mitigate defects and the resultant microstructural and mechanical properties

IN738LC is an important high performance Ni-based superalloy. Its additive manufacturing via selective laser melting (SLM), however, is rather challenging due to the cracking-prone nature of the alloy whose chemical composition contains high amount of alloying elements namely Ti and Al. We address this significant problem by this study through systematic investigations on the pre-processing, SLM optimization, and post-processing of the material, as well as using advanced analytical tools such as micro-CT. A comprehensive process map for achieving crack-free, high-density samples (similar to 99.76%) is provided. Mechanisms influencing densification, cracking and mechanical properties are discussed. Excellent mechanical properties have been achieved at both room temperature (895/1010 MPa as the yield and tensile strengths) and elevated temperature of 850 degrees C (720 MPa tensile strength and 14.4% elongation). A demonstrative as-printed turbine blade is also presented, highlighting the capability of SLM to simultaneously achieve excellent mechanical property and good geometric integrity. (C) 2019 Elsevier B.V. All rights reserved.