Effect of Annealing Temperature on Residual Stress and Microstructure of Ni60A Laser Cladding Repaired Gear

Laser cladding faces several challenges, including cracking, fracture, deformation, and interlayer delamination, which hinder its widespread application in part repair. Residual stress within the workpiece is a key factor contributing to these issues. To enhance the quality of laser cladding gear tooth repairs, the study integrates numerical modeling and experimental approaches to examine how varying annealing temperatures influence the residual stress and microstructural changes in Ni60A cladding layers. A theoretical model was established to simulate the laser cladding process and the subsequent annealing treatment utilized in gear repairs. The model was used to study the variations in temperature and stress fields at different annealing temperatures, analyze the effect of temperature gradient on residual stress, and examine the distribution of residual stress. Cladding experiments were then performed under various annealing conditions, with hardness and residual stress measurements taken from the fifth cladding layer. The results demonstrated that residual stress in the samples significantly decreased after annealing, from 781.63 MPa (RT) to 572.24 MPa (400 °C), 494.42 MPa (600 °C), and 393.83 MPa (800 °C). This indicates that the annealing process effectively reduces the residual stress in the workpiece. The residual stress values obtained from experiments showed a deviation of less than 7% from the simulation results, confirming the accuracy of the model. The highest average microhardness of 764.39 HV0.5 was observed at 600 °C. Microstructural analysis of the cladding layer revealed significant grain refinement after annealing, with previously aggregated phases transforming into a uniformly dispersed structure. Energy Dispersive Spectroscopy (EDS) analysis confirmed the presence of boron (B) in the annealed samples, which contributes to grain refinement and enhances the annealing effect.