Comparative Study on the Microstructure and Simulation of High-Speed and Conventional Fe-Based Laser-Cladding Coatings

High-speed and conventional laser cladding technologies were used to prepare Fe-based alloy cladding layers on the surface of 45 steel, compare and analyze the microstructure, microhardness, and phase structure of the two cladding layers, and study and analyze the morphology of the molten pool under the two cladding technologies, as well as the mechanism of evolution of the microstructure of the molten pool during the solidification process. The results show that, compared with the conventional laser melting coating, the grain size of the high-speed laser melting coating is finer, and the cooling rate at the top for conventional laser melting is 5.72 × 103 K/s, and the cooling rate for high-speed laser melting is 3.53 × 105 K/s. The microhardness of the high-speed laser melting coating has been significantly improved, and the solidification rates at the top for the two types of laser melting are the highest, namely 5.84 mm/s and 24.7 mm/s; the molten pool in conventional laser melting is usually larger and deeper, presenting a wide and deep shape, whereas the high-speed laser molten pool is usually shallower and narrower, with a flatter shape, presenting a comet trail, and the fast-cooling and fast-heating effects of high-speed laser melting are more significant.