Numerical simulation of the 3D propeller repair process by laser cladding of SUS316L on SUS304

Abstract

The laser cladding (LC) process is widely used for repair and surface modification; however, it generates not only high residual stress, which can negatively impact fatigue life, but also large distortions. Therefore, this study aimed to predict and minimize the residual stress and distortion of the LC process. Three numerical analyses were conducted using different finite element models to simulate the 3D propeller repair process; 3D finite element models involving conductive, convective, contact, and radiative heat transfer and requiring an element birth and death technique for expressing the additive process of LC were developed and validated experimentally. The numerical simulation results for the temperature history, distortion, and residual stress were consistent with the experimental results. Furthermore, a mismatch in the thermal contraction due to high thermal gradients and the gap in the coefficient of thermal expansion between the substrate and LC coating primarily contributed to the generation of residual stress. In addition, the effects of preheating, fixing, scanning patterns, and cooling conditions on reducing residual stress and distortion were investigated. First, preheating reduced the distortion and residual tensile stress of the LC coating owing to a decrease in the thermal gradients. Second, fixing both ends suppressed deformation without generating significantly high tensile stresses in the LC coating. Finally, optimizing the scanning pattern and allowing a cooling time between the deposition tracks to lower the interpass temperature reduced the distortion and residual stress in the entire substrate. Thus, numerical simulation can help in the prediction and minimization of the residual stress and distortions during the LC process.