Impact of hot isostatic pressing on surface quality, porosity and performance of Ti6Al4V manufactured by laser powder bed fusion: A brief review

Laser Powder Bed Fusion (LPBF) employs fast melting and solidification of Ti6Al4V powder layers to additively manufacture the desired parts. This has resulted in a sharp temperature gradient and substantial residual stress, which tend to accelerate the development of pores, non-uniform surface morphology, defects which deteriorate the fatigue and mechanical performance of parts. To address such issues, heat treatment such as hot isostatic pressing (HIP) is frequently used. Although heat treatment for LBPF parts is widely used, the importance of HIP especially on the surface quality and performance of LPBF parts is understated. As a result, the goal of this work is to summarize the impact of HIP on the surface quality, porosity, mechanical and microstructure performance of LPBF-Ti6Al4V parts. Surface morphology showed smoother surface in LPBF parts with HIP treatment by 26% reduction in surface roughness but raise a concern of contaminant forming oxide layer on the surface. HIP is highly successful in sealing pores and densifying Ti6Al4V parts up to 99.6%, which is crucial in overcoming porosity issues for LPBF parts. Due to microstructure changes from fine acicular needles a' morphology into alpha+beta phases, HIP-ed LPBF parts are found to be more ductile up to 25% from as-built parts (11.81% to 14.82%). The findings from this review encourages an in-depth investigation into the influence of HIP parameters on the surface quality and mechanical characteristics of LPBF-TI6Al4V parts for future works.