Grinding EB-PBF based additive manufactured Ti6Al4V: A surface integrity study

Abstract

Grinding is a finishing process typically done in most metallic manufacturing centers, primarily to achieve precision and surface improvement. Currently, the grinding process of titanium alloys generally requires flood coolant application. Electron Beam Powder Bed Fusion (EB-PBF) is an additive manufacturing process that uses an electron beam as the heat source to melt and fuse powder particles to build layer by layer to build a three-dimensional component. Grinding is a major secondary process applied to additively manufactured metals, but with the current methodologies, grinding may impart tensile residual stress on the surface, and thus the performance of the material under fatigue conditions is reduced. In this paper, a targeted cutting fluid application approach for grinding an additively manufactured titanium alloy is used to possibly impart a compressive residual stress upon the subsurface while also providing an improved surface roughness. This study uses samples ground with a traditional flood coolant and samples with targeted cutting fluid applications developed by the researchers. Metrics such as surface residual stress, surface roughness, microstructure, and microhardness were used to determine imparted qualities using the various grinding cooling methodologies. The results show that the subsurface maximum principal residual stresses decreased by 108%, the average surface roughness decreased by 33%, and the microhardness at 5 μm increased by 1% using targeted air as the cutting fluid compared to flood cooling while grinding additively manufactured Ti6Al4V. Overall, the targeted grinding cooling fluid application induced compressive subsurface residual stresses and reduced the average surface roughness.