High temperature material properties of IN738LC processed by selective laser melting (SLM) technology

Purpose - Selective laser melting (SLM) is being investigated by Alstom and IWF due to its flexibility, cost- and lead-time reduction potential for reconditioning of hot gas path components used in today's heavy-duty gas turbines. This paper aims to address this issue. Design/methodology/approach - Tensile tests as well as relaxation and creep tests were carried out to assess SLM processed IN738LC for use in high temperature applications. To evaluate potential anisotropic material behaviour resulting from the layer-wise build up process, all specimens were built in two directions: parallel and perpendicular to the build direction, respectively. Furthermore, extensive metallurgical investigations were made to analyse the chemical homogeneity as well as the correlation between microstructure and high temperature properties of SLM processed IN738LC. Findings - Tensile tests showed that strength properties superior to cast IN738LC can be achieved by processing this material by SLM alternatively. Due to differences in grain size, grain orientation as well as gamma'size and morphology the relaxation behaviour of SLM specimens is inferior compared to cast material. However, creep tests have shown that values within the lower scatter band of cast material can still be achieved along the build direction. Originality/value - Very limited knowledge exists regarding the processing of gamma'precipitation-strengthened nickel-base superalloys by SLM and the resulting high temperature material properties. Layered manufacturing and any lack-of-fusion porosity influences them as well as high temperature gradients, occurring during the process. This article presents the latest insights from material testing of selective laser molten IN738LC at elevated temperatures.