Surface integrity of 20MnCr5 pinion gears manufactured through laser powder bed fusion

Resumo

© 2023 The Authors.Market movement towards sustainability and electromobility impose new demands on the gear Industry in terms of materials, design and manufacturing. In this context, laser powder bed fusion (L-PBF) has been under the spotlight for being one of the most promising technologies in additive manufacturing (AM), allowing the designer to think beyond traditional constraints. On the other hand, anisotropic properties, distortions, and heterogeneous residual stress may lead to excessive stress states during finishing processes. For carburizing materials, such as 20MnCr5, the mechanisms leading to residual stress and distortions go beyond the temperature gradient mechanism (TGM) and incorporate significant microstructural changes due to phase transformation. The combination of these phenomena with the gear manufacturing chain places a significant challenge to the gear industry. Therefore, this study investigates the potential and challenges of manufacturing 20MnCr5 gears through L-PBF with focus on the surface integrity evolution along the manufacturing chain. The study addresses the processability of the material and investigates the surface integrity of the gears through the manufacturing chain. The composition of thermal and microstructural phenomena simultaneously occurring during print generates heterogeneous residual stress along the gear orientation. Contrary to the literature, the stress relief did not equalize the residual stress entirely. Therefore, the heterogeneous residual stress distribution observed in the as-built condition propagated through the entire chain. Even after three manufacturing operations, the pattern of residual stress after printing directly influenced the final residual stress state.