Microstructure evolution and properties of (Nb,M)C (M=Ti,V and Zr) reinforced Ni-WC coatings by laser cladding

To enhance the surface properties of AISI 1045 steel, high-performance composite carbide-reinforced coatings were prepared using laser cladding technology. Specifically, (Nb,M)C (M = Ti, V, and Zr) reinforced Ni-WC coatings were developed. The effects of various composite carbides on the microstructure and properties of the coatings were examined through a combination of first-principles calculations and experimental methods. Initially, the microstructures of (Nb,M)C (M = Ti, V, and Zr) were constructed using first-principles calculations, and the microscopic mechanical and electronic properties of these composite carbides were determined. The impact of different doping elements on the properties of the composite carbides was investigated. Subsequently, an in-situ synthesis system was designed to fabricate the composite coatings. The feasibility of synthesizing the composite carbides (Nb,M)C (M = Ti, V, and Zr) within the laser cladding coatings was confirmed using XRD, SEM, and EDS techniques. Additionally, the formation mechanism of the composite carbides was analyzed. Under different element doping conditions, the reinforcement phase in the composite coating exhibited various grain morphologies, with (Nb0.5Ti0.5)C grains showing the best particle size and density. Microalloyed interfaces were observed at the WC interfaces in each coating, indicating strong bonding between WC and the FCC matrix. The presence of WC also improved the fineness of the surrounding phase structure. Due to differences in kinetics and thermodynamics, a core-shell structure of (Nb0.5Ti0.5)C-core and WpC-shell was observed in the (Nb0.5Ti0.5)C coating. Friction-wear tests revealed that this core-shell structure helps alleviate crack sensitivity between the reinforcing phase and the matrix. Hardness analysis showed that the average hardness of the (Nb0.5Ti0.5)C, (Nb0.5V0.5)C, and (Nb0.5Zr0.5)C coatings was 62.89 HRC, 60.91 HRC, and 58.27 HRC, respectively. Among these, (Nb0.5Ti0.5)C demonstrated the most significant hardness enhancement for AISI 1045 steel, achieving a 3.51-fold increase. In the friction and wear tests, the (Nb0.5Ti0.5)C coating exhibited the best wear resistance. The primary friction-wear mechanisms of the coatings were found to be adhesive wear, oxidative wear, and minor abrasive wear. These research findings provide a theoretical basis for the preparation of high-performance composite carbide-reinforced coatings using laser cladding. © 2024 Elsevier B.V.