K418合金叶片激光再制造Inconel718覆层匹配与强化

为了解决K418合金叶片再制造熔覆层易开裂、结合界面处力学性能较差等难题,采用具有输入可调控、热输入可控制以及降低熔池及热影响区温度等优势的脉冲激光,得出在工艺参量为激光功率2.5kW、送粉速率37.5g/min、扫描速率8mm/s,载气气流3L/min下,K418基体与Inconel718熔覆层之间能够形成良好的冶金结合。结果表明,熔覆层显微组织依次由界面处平面晶、底部胞状晶、中部树枝晶及顶部等轴晶组成;经过对比优化下的工艺参量,获得了成形质量良好且无明显裂纹、气孔等缺陷的Inconel718熔覆层;通过基体与覆层的硬度测试,覆层整体硬度值在300HV左右且分布较为均匀,基体平均硬度在400HV以上、结合界面处硬度值为460.46HV,相对于基体提升了12%;物相形分析表明,Inconel718熔覆层与基体K418性能匹配较好,激光再制造凝固成形时经历了L→γ→(γ+MC)→(γ+laves)的凝固过程,脉冲激光的热输入对基体K418合金热影响区完成了γ′相的固溶再析出过程,界面处沿晶界析出少量的二次析出相laves相和MC相对熔覆层及界面处晶界起到钉扎晶界、阻碍滑移的强化作用。试验相关工艺及参量为K418叶片激光再制造提供了借鉴和分析。

Matching and strengthening between Inconel718 cladding and K418 alloy blades by laser remanufacturing

The cladding layer of K418 alloy blade after remanufacturation was easy to crack and the mechanical properties of bonding interface were poor. In order to solve these problems, the pulsed laser with the advantages of adjustable input, controllable heat input and lower temperature of molten pool and heat affected zone was used. Good metallurgical bonding was formed between K418 matrix and Inconel718 cladding layer under the conditions of laser power 2.5kW, powder feeding rate 37.5g/min, scanning rate 8mm/s and carrier gas flow 3L/min. The results show that the microstructure of the cladding layer is composed of plane crystal at the interface, cell crystal at the bottom, dendrite in the middle and equiaxed crystal at the top. Under the optimized process parameters, Inconel718 cladding layer with good forming quality and without obvious cracks and pore defects is obtained. After the test of the hardness of the matrix and the coating, overall hardness of the coating is about 300HV and the distribution is uniform. Average hardness of the matrix is above 400HV, and the hardness of the bonding interface is 460.46HV, which is 12% higher than that of the matrix. Phase analysis shows that, the properties of Inconel718 cladding layer and matrix K418 match well. The solidification process of laser remanufacturing is L→γ→(γ+MC)→(γ+laves). Solid solution and precipitation of γ′ phase in heat affected zone of matrix K418 alloy are completed by heat input of the pulsed laser. A small amount of secondary precipitates is precipitated along the grain boundary at the interface. Laves phase and MC phase can pin the grain boundary and hinder the slip of the cladding layer and the grain boundary at the interface. The related process and parameters can be used for reference and analysis of K418 blade laser remanufacturing.