Research on the Microstructure and Properties of QT400-18 Laser Cladding Remanufacturing

To address the failure issue of local wear in QT400-18 transition shafts used in high-speed trains, laser cladding remanufacturing of a ductile cast iron surface was carried out using 45 wt.%Fe + 55 wt.% Inconel625 powder. The phase composition, microhardness, interfacial bonding strength, and wear resistance of the cladding layer were analyzed. The results show that the cladding layer is primarily composed of a γ (Ni, Fe) solid solution and a small amount of eutectic carbides. The microstructure of the cladding layer forms columnar dendrites, cellular dendrites, and equiaxed crystals from bottom to top. The microstructure of the single-layer, single-pass interface consists of ferrite, acicular martensite, and ledeburite, while the multi-layer, multi-pass interface consists of ferrite, granular pearlite, and discontinuous ledeburite. The average microhardness of the single-layer, single-pass cladding layer is approximately 350 HV0.5, and the hardness of the fine-grained and coarse-grained regions of the multi-layer, multi-pass cladding layer is approximately 330 HV0.5 and 250 HV0.5, respectively. The interfacial bonding strength reaches 96.5% of the base material strength. The wear mechanism of the cladding layer is mainly mild abrasive wear, with significantly better wear resistance than the base material.