Effect of in-situ ultrasonic impact treatment on residual stress of laser deposition layer

Ultrasonic impact treatment (UIT) could improve the residual stress of additive manufactured parts. However, there is almost no report on the effect of in-situ UIT, where the UIT equipment moves with laser metal deposition (LMD) equipment at a controllable offset, on residual stress. In this work, the effect of in-situ UIT on residual stress and the effect of offset on the effectiveness of in-situ UIT were investigated by finite element analysis. The stress change introduced by in-situ UIT includes the impact and cooling process. The results show that the value of residual compressive stress (RCS) introduced by the impact of in-situ UIT is higher than that after ex-situ UIT. In the cooling process, the unfinished shrinking behavior reduces it. The increasing offset has little influence on the residual stress field introduced by the impact of in-situ UIT. Residual compressive stress (RTS) reappears in the deposition layer after the cooling process of in-situ UIT, when the offset is small, increasing the offset can retain the RCS. In-situ UIT can improve the residual stress field and the impact of in-situ UIT becomes increasingly similar to that of ex-situ UIT as the offset increases. The findings serve as invaluable guidance in devising strategies to manage and mitigate residual stress in components produced by LMD and other additive manufacturing techniques.