Evaluation of Residual Stress Distribution in Additively Manufactured Inconel 625 using Finite Element Analysis and Experimental Investigations

Laser powder bed fusion (LPBF) holds significant promise in aerospace and various high-tech industries due to its adaptable manufacturing capabilities and the creative design possibilities it offers. Nevertheless, several factors, such as elevated residual stresses, unpredictable porosity, and dimensional accuracy, can impact the quality of components and hinder the widespread adoption of LPBF in industrial applications. Residual stresses are inherent to laser-based processes, and there is a current emphasis on research efforts to effectively manage these stresses. Developing an accurate numerical model to predict residual stresses in LPBF is vital for comprehending how processing parameters impact component quality.

This study investigates the impact of laser power and scanning speed on the magnitude and distribution of residual stresses in Inconel 625, employing a set of test coupons manufactured with the EOS 290 machine. The research adopts a comprehensive methodology, incorporating both finite element simulations and experimental analyses. Assessment of residual stresses extends beyond the coupon's surface, including evaluations throughout its depth in both longitudinal and transverse orientations.

Six distinct process conditions we examined, involving three levels of laser power (100 W, 200 W, and 240 W) and three levels of scanning speed (750 mm/s, 1000 mm/s, and 1500 mm/s). In all six scenarios, both simulation and experimentation consistently revealed a gradual increase in tensile residual stress as depth below the surface increased in the area of interest. Notably, increasing the laser power from 100 W to 240 W at a constant speed generally resulted in higher tensile residual stresses as depth increased beneath the surface. These trends were corroborated by both the simulation and experimental measurements. Furthermore, it was evident that the increase in laser power from 100 W to 240 W had a more pronounced effect on residual stress values compared to variations in scanning speed.