Exploring the post-heat treatment on the electropolishing characteristics of laser powder bed fusion processed Inconel 718 superalloy

The influence of post-heat treatment on the microstructural and electropolishing characteristics of the laser powder bed fusion processed Inconel 718 is studied. The electropolishing results show a significant decrease in the surface roughness for as-printed (∼69%) and post-heat treatment conditions (∼74%) with increasing current density and polishing time. The surface morphology of the as-printed samples showed the presence of unaltered asperities on the electropolished surface, which can be attributed to the precipitation of non-conductive lave phases and metal carbides during laser powder bed fusion processing. The post-heat treatment homogenizes microstructure and dissolves these phases in the metal matrix along with the precipitation of strengthening phases. As a result, the surface morphology of post-heat treatment samples becomes more uniform, signifying fewer surface irregularities. The statistical parameters show a significant reduction in sharp asperities in the post-heat treatment condition. The material ratio curves revealed uniform material distribution in the post-heat treatment samples, signifying reduced surface asperities compared to as-printed conditions.