薄壁锡青铜焊接零件的微区激光熔覆修复

Micro-Laser Cladding Repairing of Thin-Walled Bronze Welded Part

在航空发动机用轴向燃油柱塞泵的工作过程中,燃油介质中的气泡随压力变化破裂,导致转子组件底面处的铜合金极易受到气蚀损伤。激光熔覆具有输入能量可控、熔覆层组织致密,且可与基体实现冶金结合等优点。为解决转子组件报废率过高的问题,本研究采用激光熔覆手段,将等离子旋转电极雾化制粉工艺制备的粉体熔覆至转子组件底面的铸造锡青铜损伤部位,进行了铸造锡青铜微区熔覆修复的可行性探索,并分析熔覆层的微观组织和局部的力学性能。结果表明,熔覆层铜合金成分基本无烧损,显微组织为细小的δ相(Cu_(31)Sn_(8))填充α-Cu枝晶组织,且未见热裂裂纹。熔覆层抗拉强度为313~339 MPa,伸长率为23.5%~24.0%,硬度为118HV0.2~119HV0.2,摩擦因数<0.003,自然腐蚀电位为-0.205~-0.230 V,其与基体的结合强度(剪切)为285.8~328.5 MPa,各项性能均优于基体的。对力学试样断口的观察结果表明,其主要断裂形式为延性断裂,及伴随未熔粉末导致的微孔聚集断裂。分析可知,脉冲激光所带来的大温度梯度是形成细小枝晶微观组织的主要原因,而细小的组织结构则是熔覆层呈现良好性能的主要原因。

During the working process of fuel plunger pump for aero-engine,the bubbles in the fuel constantly burst with the change of pressure,resulting in the cavitation damage in the bronze layer welded on the bottom of the rotor part.Laser cladding has the advantages such as controllable input energy,dense structure of the cladding layer,and metallurgical bonding with the substrate.In order to reduce the scrap rate of plunger pump rotors,we adopt the laser cladding process to clad the bronze powders prepared by the PREP process on the damaged bronze part,realize the feasibility exploration of the micro-area cladding repair of the cast bronze,and analyze the microstructure and local mechanical property of the cladding layer.The results show that the bronze composition of the cladding layer has basically no burning loss,that the microstructure is a fine dendrite structure,withδphase(Cu_(31)Sn_(8))filling theα-Cu dendrite,and that no hot cracks are found in both the cladding layer and bronze substrate.The tensile strength of the cladding layer can reach 313-339 MPa,the elongation can reach 23.5%~24.0%,the hardness is between 118HV0.2-119HV0.2,the coefficient of friction is less than 0.003,the self-corrosion potential is between-0.205-0.230 V and the bonding strength(shear strength)between the cladding layer and bronze substrate is up to 285.8-328.5 MPa.Observation of the sample fracture surface shows that the main fracture mode is the ductile fracture,accompanied with the micropore aggregation fracture,which is caused by the unmelted powders.The analysis shows that the large temperature gradient is the main reason for the formation of the fine dendrite microstructure,and the fine organization structure is the main reason for the good performance of the cladding layer.