7050铝合金表面Al/Ti激光熔覆工艺实验及温度场模拟分析

Process Test and Temperature Field Simulation of the Al/Ti Laser Cladding Coating Above 7050 Aluminum Alloy

在7050铝合金表面激光熔覆Al/Ti复合粉体,通过3因素3水平正交试验得知当激光功率为1.5 k W,扫描速度为150 mm/min,离焦量为50 mm时熔覆层质量最优。模拟计算得到正交试验工艺参数下的光斑中心最高温度值,并利用极差分析得到:正交试验因素对中心点最高温度值影响程度从大到小的顺序是扫描速度V,激光功率P和离焦量S。通过对9组试样熔池尺寸及不同位置点温度随时间变化趋势分析可以得到,试样前端结合较差是由于熔覆过程中基体熔池深度较小,不足以使基体与熔覆材料很好地结合;而后端都出现的不同程度的变形和烧蚀,是末端温度急剧积累引起的。通过分析Al/Ti熔覆层的金相组织可知,熔覆层组织以胞状树枝晶为主,且分布均匀细密。

Based on the process of laser cladding A1/Ti composite powder above 7050 aluminum alloy, and by using an orthogonal experiment, an optimized cladding coating parameters are achieved with the laser power of 1.5 kW, the scanning speed of 150 mm/min and the defocusing amount of 50 mm. The highest temperature in the laser spot center is obtained from the simulation under the parameters in the orthogonal experiment. Using the range analysis, the relative significances of the three respective parameters, laser scanning speed V, laser power P and defocusing amount S are achieved in the order, from big to small. By analyzing sizes of the molten pool and several typical curves of sample temperature changing with the scanning direction in the condition of the orthogonal experiment, it has been discerned that the bonding strength of the sample front is poor because its molten pool depth in the substrate is too small to obtain a good combination between the cladding material and the substrate; moreover, the deformation and ablation occur at the sample end due to the substantial temperature accumulation origining from its poor heat dissipation. The grain morphology of A1/Ti cladding coating is mainly cellular dendrites with equal and dense distributions.