Suppression of epitaxial grain growth in laser powder bed fusion fabricated Inconel 625 through intermittent variation of the build layer thickness

Abstract

Microstructural anisotropy, which often leads to anisotropy in the mechanical performance, induced by the epitaxial grain growth during solidification is a major concern in a number of metal and alloy components that are manufactured using the additive manufacturing technique of laser powder bed fusion (LPBF). In this work, we demonstrate that a periodic variation in the layer thickness during LPBF results in the alteration of the grain growth direction and can effectively suppress the formation of columnar grains. Such a build strategy simultaneously decreases the grain size and the texture intensity, resulting in a reduced anisotropy in the mechanical properties. The variation of grain growth direction can be rationalized by thermal gradient variation near the transition area that occurs after the layer thickness is altered. This simple strategy provides an additional and new tool for grain structure tailoring during LPBF.