Effect of Buildup Angle and Post Laser Powder Bed Fusion Heat Treatment on Plasma Electrolytic Polishing of Additively Manufactured Ti–6Al–4V Coupons

Cyclic plasma electrolytic polishing (C‐PEP) processes are performed on additively manufactured (AM) Ti–6Al–4V coupons produced by laser powder bed fusion (LPBF) to address the effects of buildup angles and post‐LPBF heat treatment. The varied buildup angles result in distinct morphological and microstructural features and structural defects, particularly on the down‐skin surface due to the termination of melt pools on the coupon surface as well as the nonfully‐melted feedstock particles. These variations influence the post‐LPBF heat treatment and the polishing efficiency. Typically, lower buildup angles result in higher surface roughness and, particularly, higher down‐skin roughness than that of the up‐skin, which exhibits a correlation with the current density and electrolyte temperature during the C‐PEP Process. An extrinsic phase, γ ₁ , is detected by X‐ray diffraction after the post‐LPBF heat treatment, and the phase composition increase with the buildup angles. Strikingly, the C‐PEP process induces another extrinsic phase, γ ₂ , alongside γ ₁ , on the heat‐treated coupons rather than on the as‐built ones. The γ ₂ phase compositions also increase with the buildup angles. Both the γ ₁ and γ ₂ phases can be completely removed by chemical etching. A mechanism is proposed, combining the post‐LPBF heat treatment and C‐PEP, to understand and interpret the observed phenomena.