Enhanced fatigue performance of laser directed energy deposition fabricated Ti6Al4V alloy using laser shock peening

Abstract

Additively manufactured parts generally have lower fatigue life than their wrought counterparts as a result of the nature of deposition, defects, extreme thermal gradients, and residual stresses generated during the process. The present study explored a high-layer thickness laser-directed energy deposition (LDED) of Ti6Al4V and enhancing its fatigue life by using laser shock peening (LSP). Significant improvements in the fatigue life in samples 1 and 4 were observed for the LDED+LSPed samples as compared to only LDED samples. However, for samples 2 and 3, a slight decrease in fatigue life were observed for LDED+LSPed samples. This can be due to the presence of internal defects on the LDED+LSPed samples or surface cracks or uneven distribution of LSP on the surfaces. A ductile mode of fatigue failure was observed with multiple cracks (both point and line cracks) on the failed surface. River lines with multiple tributaries as well as striation regions with clear signs of incremental crack growth were also observed. The present paper presented the high layer thickness LDED for faster part fabrication and enhanced fatigue life using LSP as a post-processing method. This will help in reducing the manufacturing time while also improving the fatigue life as compared to other AM processes.