In-situ NbC reinforced Fe-based coating by laser cladding: Simulation and experiment

• Published in: Surface & coatings technology 2021-04, Vol.412, p.127027, Article 127027
• Main Authors: Chen, Liaoyuan, Yu, Tianbiao, Xu, Pengfei, Zhang, Bo
• Format: Article
• Language: English
• Subjects: Abrasive wear; Adhesive wear; Boron carbide; Carbon steels; Coatings; Composite coating; Finite element model; Grain boundaries; Hardness; In-situ reaction; Iron; Laser beam cladding; Laser cladding; Marangoni convection; Mechanical properties; Niobium carbide; Phase composition; Solid solutions; Solidification characteristics; Strengthening; Substrates; Synthesis; Wear mechanisms
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2021.127027

In-situ NbC reinforced Fe-based coating was fabricated on the middle carbon steel surface by laser cladding with the mixture of niobium and boron carbide powder, aiming at revealing the mechanism of in-situ synthesis and improving the hardness and wear performance. The possibility and mechanism of in-situ synthesis were explored for the first time by combining simulation with experiment. The phase composition, microstructure characteristics and evolution mechanisms of the coatings were investigated by X-ray diffraction and scanning electron microscopy. The strengthening mechanism of hard phases on hardness and wear performance of coating were analyzed in detail. The results show that Marangoni convection promoted the melting of particles and improved the uniformity of solute atoms. The composite coating is mainly comprised of reinforced phases (NbC, Fe2B, B4C) and the matrix ([FeCr] solid solution). The dispersive NbC particles (average diameter ~ 1.03 μm) in-situ formed at the grain boundary achieved the dispersion and fine-grained strengthening effect. The hardness of the composite coating is 866.36 HV0.5, which is 3.95 times and 4.16 times that of the substrate and Fe-based coatings. The volume loss of composite coating reduced more than five times as compared to the substrate and Fe-based coating, and the wear mechanism changed from abrasive wear to adhesive wear due to the addition of Nb and B4C powders. •In-situ NbC coating was deposited on the 45 steel surface with Nb and B4C powder.•The in-situ reaction mechanism and phase evolution were elucidated in detail.•In-situ NbC phase (average diameter ~ 1.03 μm) can refine the microstructure.•The composite coating has the highest hardness and lowest wear volume.