In-situ monitoring of substrate deformation in directed energy deposition process using the coherent gradient sensing method

Abstract In recent years, additive manufacturing (AM) has become one of the most promising manufacturing technologies. To enhance quality, in-situ monitoring for AM processes has drawn considerable attention from researchers. Although progress has been made for in-situ monitoring of the directed energy deposition (DED) process, there are still challenges that must be addressed to improve the manufacturing quality. To solve the problem of achieving both high resolution and step-wise evolution of full-field deformation during in-situ monitoring of AM, we propose the coherent gradient sensing (CGS) method for in-situ monitoring of the DED process in this study. A CGS system was designed to perform in-situ monitoring during the DED process. The real-time full-field deformation of a thick substrate was measured for the first time in the cladding process of a disc-shaped specimen, in which the deformation distribution characteristics at different locations were analyzed. During the first layer cladding process, the deformation evolution of the substrate can be divided into three bending stages: U-type, S-type, and transitional. Our results show a significant relationship between the boundary R of deformation distribution in the y-axis at different stages and the radius r of the disc-shaped specimen: R = 3/5 r, with R being the boundary of deformation distribution and r being the radius of the disc-shaped specimen. The experimental results reveal that the relationship between the in-situ deformation evolution of the substrate and the deposition track at different stages can be effectively monitored using a CGS system. Furthermore, the obtained results can offer useful reference for improving the quality of components that are repaired or remanufactured using DED technology.