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

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, with δ phase(Cu₃₁Sn₈) filling the α-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.