为了改善熔覆层几何形貌特征,研究了激光熔覆后残余应力的分布规律。以稀释率与宽高比为评价指标,基于响应曲面法开展了4因素(激光功率、扫描速度、送粉量、离焦量)、5水平中心复合设计矩阵试验。在单因素和多因素交互作用下,研究了熔覆参数对各响应值的影响规律。研究结果表明:扫描速度和离焦量对宽高比的影响最显著,离焦量和激光功率对稀释率的影响最显著,且激光功率和扫描速度的交互作用对稀释率存在影响。最后试验验证了预测模型的准确性。选取优化后的熔覆层形貌和工艺参数进行数值模拟,发现x方向的最大残余拉应力为532 MPa且位于熔覆层末端。在熔覆层纵剖面上,残余应力在沉积层及热影响区主要表现为拉应力;随着深度的增加,拉应力逐渐减小并在基体底部转变为压应力;在y方向上,由于成形件的形变,基材底面受到的是拉应力。

In order to improve the geometrical features of the cladding layer and to explore the distribution law of residual stress after laser cladding, we use dilution ratio and width-height ratio as the evaluation indexes. Based on the response surface method, a composite design matrix test with 4 factors (laser power, scanning speed, powder feeding rate and defocusing amount) and 5 horizontal centers is established. The influence laws of cladding parameters on each response value under the interaction of single factor and multiple factors are explored. The research results show that scanning speed and defocusing amount have the most significant influence on width-height ratio, defocusing amount and laser power have the most significant influence on dilution rate, and the interaction between laser power and scanning speed has certain influence on dilution rate. Finally, the correctness of the predictive model is verified by experiments. The optimized morphology and process parameters of the cladding layer are selected for numerical simulation, and it is found that the maximum residual tensile stress in the x direction is 532 MPa and occurs at the end of the cladding layer. In the longitudinal section of the cladding layer, the tensile stress mainly appears in the cladding layer and the heat-affected zone. As the depth increases, the tensile stress gradually decreases and is converted into the compressive stress at the bottom of the cladding layer. However, in the y direction, due to the deformation of the formed parts, the bottom surface of the substrate is subjected to tensile stress.