In-situ residual deformation field analysis of laser repaired metal components by coherent gradient sensing method

Abstract

Directed Energy Deposition (DED) technology plays an important role in metal additive manufacturing and remanufacturing. However, the quality and repeatability of DED products are still regarded as a challenge that hinders their widespread applications, especially in cutting-edge sectors. As a promising approach to meet that challenge, the in-situ monitoring of mechanical quantities during DED process, such as deformation and stress, has attracted extensive attention in both academic and engineering fields. In this study, a coherent gradient sensing (CGS) system that matches DED equipment is developed and used for in-situ monitoring the residual deformation of DED repaired metal components. The accuracy of the CGS system has been verified by measuring the curvature of a spherical mirror, and the relative error of the curvature is within 2.5% as a whole. Then, through single-layer/double-layers repair experiments, the influence of dwell time between adjacent tracks, cooling process between adjacent layers, and scanning path of the second layer on the residual deformation are analyzed. In single-layer repair experiment, the value of residual deformation increases with the dwell time, while its distribution characteristic almost keeps the same. In double-layers repair experiment, the anisotropy of residual deformation field is mainly influenced by the deposition direction of the second layer. Compared with parallel deposition path in double-layer repair experiment, the orthogonal deposition path results in a reduction of both the anisotropy and the maximum value of residual deformation field. Moreover, in the cooling process of orthogonal deposition, the residual deformation increases while the distribution characteristic remains unchanged. In conclusion, the feasibility of residual deformation measurement by CGS method in DED repairing process is verified, which provides both data support and tool for the future industrial application.