9 - Residual stress in laser powder bed fusion

Abstract

Laser powder bed fusion (L-PBF) has great prospects for biomedical, automotive, aerospace, and other high-tech industry sectors due to its manufacturing flexibility and design freedom. However, several factors that include high residual stresses, random porosity, and dimensional accuracy can affect the quality of parts and hamper L-PBF progress and widespread industrial applications. Residual stresses are inherent in laser-based processing, and focused studies to control these stresses are topical. Thermal and mechanical post-processing methods, such as stress-relief heat treatment and machining, can relieve residual stresses but cannot reverse in situ stress-induced distortions or cracking. Thus, in situ stress relief remains an attractive option/complement for managing the effect of residual stress on part strength, surface integrity, and dimensional accuracy. Better still, combining in situ and post-processing stress-relief techniques could be a more effective approach to residual stress control. This chapter presents a detailed analysis of the residual stress control techniques that can be applied in L-PBF. Recommendations for effective evaluation and appropriate selection of residual stress management techniques are outlined.