Investigation of surface finish and fatigue life of laser Powder Bed fused Ti-6Al-4V
Kannan Pradeep Varsha, Swee-Hock Yeo, Hitoshi SOYAMA
Abstract
• Effects of Hydrodynamic Cavitation Abrasive Finishing (HCAF) and Laser Cavitation Peening (LCP) were compared. • Improvements of fatigue strength of AM Ti6A4V by HCAF and LCP were revealed experimentally. • Introduced compressive residual stress was 62 MPa by LCP and 40 MPa by HCAF. • LCP improves fatigue strength by 75% comparing with as-built specimen. • Estimation methods of fatigue strength improvements by surface roughness and residual stress were proposed. In this fact-pacing world of technological advancement, the rise of additive manufacturing (AM) has found immense applications of metallic alloys such as Ti6Al4V to manufacture key components in automotive, aerospace and healthcare sectors. However, fatigue characteristics of such additively manufactured metal alloys is noticeably weak, and as such requires post-processing. In this study, AM Ti6Al4V manufactured by Laser Powder Bed Fusion (L-PBF) was treated by Hydrodynamic Cavitation Abrasive Finishing (HCAF) and Laser Cavitation Peening (LCP) to observe the improvement in surface roughness as well as fatigue performance. Our investigations revealed a substantial improvement in surface quality post-HCAF processing. Notably, the surface roughness of AM Ti6Al4V specimens showed a significant reduction of about 91.2 %, post surface treatment. However, Laser Cavitation Peening (LCP) treated sample demonstrates a significantly enhanced fatigue strength of 393 ± 22 MPa at 10 7 , which was 1.75 times better than that of as-built one, i.e., 224 ± 16 MPa. This difference can be attributed to the distinct surface modification mechanisms of each technique. LCP, utilizing laser-induced shock waves, likely induces large compressive residual stresses, leading to better fatigue resistance.