Grain boundary and triple junction characteristics analytics of additive manufactured Inconel 625 superalloy using selective laser melting

Abstract

Selective laser melting (SLM) is a rapidly developing technology with many advantages over traditional manufacturing methods. SLM is gaining popularity in many industries due to its potential to revolutionise designs and efficiency. To facilitate more widespread adoption of the technology, it is vital to understand the microstructure characteristics of materials produced by it. In this study, IN625 superalloy were produced by SLM are analysed by microstructural characteristics including grain boundaries and triple junctions and mechanical properties by hardness. Electron backscatter diffraction (EBSD) and data analysis were employed to investigate the effect of SLM on grain structures, crystal orientation distribution, grain boundary characteristic distribution (GBCD) and triple junction characteristic distribution (TJCD) in IN625. Investigation of microstructure characteristics revealed that there is increase in the volume of grain boundaries and dislocation barriers perpendicular to the build direction. The grain boundaries in the SLM manufactured IN625 superalloy were found to be mostly low angle (<15°) and further investigation on triple junctions revealed that the majority of triple junction's present being the preferred type of triple junctions where two or more low angle or coincidence site lattice (CSL) grain boundaries meet. High volume of low angle boundaries, anisotropic microstructure and preferred type of triple junctions found in SLM manufactured IN625 leads to increase in the failure resistances when compared to conventional manufactured IN625. These microstructures were anisotropic in nature which leads to anisotropic mechanical properties.