针对在K418薄壁叶片上局部再制造的多层立体成形组织难以调控优化的难点,开展该类合金激光再制造覆层工艺及组织研究。优选三组工艺进行Inconel 718成形试验,观察覆层显微组织,测试其力学性能,对比分析并进行单道多层立体成形试验。成形优化工艺的参数为激光功率为1.2 kW、扫描速度为300 mm/min、送粉速率为25 g/min、气体流速为3 L/min、脉宽为10 ms、占空比为1∶1。试验结果表明:单道覆层与基体形成了良好的冶金结合,高度和宽度分别为1.537 mm、1.414 mm,覆层主要由细小致密的等轴枝晶、定向生长的柱状枝晶和胞状晶组成,覆层显微硬度为263.7~289.7 HV0.2;多层立体成形总高度为3.67 mm,显微硬度范围为284.3~315.5 HV0.2,底层覆层析出Laves、MC和γ″相,弥散强化合金,提高了底部覆层的硬度。

Controlling and optimizing the local remanufactured multilayer stereo forming microstructures of K418 thin-walled blades is a difficult task. This study investigates a laser-based remanufacturing coating process and microstructure control of K414 alloy. The alloy is coated with Inconel 718. The formation of Inconel 718 is tested by three processes, which are used for observing the microstructure of the coating, testing mechanical properties, and then comparing, analyzing, and conducting a single-channel multilayer stereo forming test. According to the test results, the optimal coating parameters are as follows: laser power is 1.2 kW, scanning speed is 300 mm/min, powder feeding rate is 25 g/min, gas flow rate is 3 L/min, pulse width is 10 ms, and duty ratio is 1∶1. The matrix combining with a single coating forms a strong metallurgical bonding with height of 1.537 mm and width of 1.414 mm. The coating mainly consists of fine and dense equiaxed crystal dendrites, oriented columnar dendrites, and cell crystals. The microhardness of the coating is 263.7-289.7 HV_0.2. The total height of a multi-layer three-dimensional formation is 3.67 mm with a microhardness range of 284.3-315.5 HV_0.2. The bottom layer is coated with Laves, MC, and γ'' phases. The hardness of the bottom layer is increased by the dispersion-strengthened alloy.