Effect of NbC in-situ synthesis on the microstructure and properties of pre-placed WCoB-TiC coating by laser cladding

• Published in: International journal of advanced manufacturing technology Vol. 120; no. 1-2; pp. 1265 - 1280
• Main Authors: Zhang, Hao, Pan, Yingjun, Zhang, Yang, Lian, Guofu, Cao, Qiang, Zhu, Xingyu
• Format: Journal Article
• Language: English
• Published: London Springer London 01.05.2022; Springer Nature B.V
• Subjects: CAE) and Design; Coatings; Computer-Aided Engineering (CAD; Crack propagation; Dilution; Elastic properties; Electron probes; Engineering; First principles; Fracture toughness; Industrial and Production Engineering; Laser beam cladding; Mechanical Engineering; Media Management; Metallicity; Metallurgy; Microhardness; Microstructure; Niobium carbide; Optical microscopes; Original Article; Phases; Scanning electron microscopy; Substrates; Synthesis; Titanium carbide; Transgranular fracture; WCoB-TiC composite coating; Laser cladding; Microhardness; NbC; Fracture toughness
• ISSN: 0268-3768; 1433-3015
• DOI: 10.1007/s00170-022-08844-7

WCoB-TiC composite coatings with in-situ formation of NbC were fabricated on the surface of an AISI 1045 substrate by laser cladding. The geometric characteristics, microstructure, microhardness, and fracture toughness of coatings were investigated by means of an optical microscope (OM), a scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), an electron probe microanalyzer (EPMA), and a microhardness tester. In addition, the elastic constants and bulk property of the reinforced phases were investigated by first principles calculation. The results showed that a reliable metallurgical bonding was formed between the coating and the substrate and in-situ synthesized reinforcement phases of the coating consisted of WCoB, W 2 CoB 2 , TiC, NbC, (Nb,Ti,W)C, and traces of Nb 2 C. The dilution rate and porosity had a negative effect with the addition of Nb. According to the results of SEM, EDS, and EPMA, Nb was diffused uniformly in the TiC structure. The NbC phase had the highest hardness among all in-situ synthesized reinforcement phases, which reached 24.525 GPa, while Nb 2 C reflected the strongest metallicity. The microhardness and fracture toughness of the coating were increased firstly and then decreased following the increase of Nb content, and when the Nb addition was 4 wt%, the coating had the highest average microhardness and fracture toughness (1755.42 HV 0.5 , 8.23 MPa·m 1/2 , respectively). The microhardness and fracture toughness was 24% and 30% higher than that of the coating without Nb addition, respectively. From the crack propagation morphology of coatings, all coatings had fine transgranular fracture.