Quantifying peening effectiveness in SS316L workpieces produced by laser powder bed fusion: Hardness, residual stresses, and image processing insights

This paper presents an in-depth study on the shot peening of SS316L workpieces fabricated using Laser Powder Bed Fusion (LPBF) techniques. The study encompasses experimental evaluation of hardness and residual stresses, as well as the development of a residual stress equation tailored to LPBF-processed materials. The research aims to enhance the understanding of how shot peening parameters like shot size, duration of peening and rotation of the work part influences the mechanical properties and residual stress distributions in these SS316L materials. A novel approach was used to analyze the effectiveness of peening through image processing techniques, where the percentage of the targeted area versus the actual peened area, termed as %area of peening, was quantified. Identified the best parameters of shot peening which has led to high percentage area of peening and this led to the improvement in hardness from 240 to 490 Hv and more compressive residual stress of magnitude −780 MPa. The proposed 2D and 3D image processing method has been successfully validated across three different heat treatment conditions of SS316L, including heat treatment at 900°C, 600°C, and the as-built condition. The developed residual stresses serves as a predictive tool for engineers to tailor peening treatments to specific material requirements.