Study on Grain Size Control Method of Laser Cladding on Surface of EA4T Axle

In order to meet the service requirements of EA4T axle, the cladding layer of the remanufactured axle is required to reach 5 th grade grain size standard, which poses a challenge to the epitaxial growth grain control of the laser cladding process with directional solidification feature. Two controlling methods of grain size including adding heterogeneous nucleating agent and processing control were compared and evaluated in terms of forming quality, grain size and mechanical properties of cladding layer. The results show that the addition of heterogeneous nucleating agents can improve the grain size to level 5 by promoting the grain nucleation while the increased molten pool viscosity leads to poor formability of the cladding layer, which is easy to produce metallurgical defects such as lack of fusion and micro-cracks. On the other hand, the reduction of spot diameter or increase of scanning speed can promote the grain refinement by increasing the cooling rate of the molten pool, increasing the grain size of the cladding layer to level 5 and ensuring the good formability and mechanical properties of the cladding layer. This study provides a clear direction for the grain size control of laser cladding and lays a theoretical and technological foundation for laser remanufacturing of high-performance axles.