Effect of CeO2 Content on Microstructure and Properties of Ni-Based Tungsten Carbide Layer by Plasma Arc Cladding

A Ce-containing Ni-based tungsten carbide layer was prepared on the surface of Q345 steel by plasma arc cladding technology. The effect of CeO2 additions on the microstructure and properties of the Ni-based tungsten carbide cladding layer was investigated. The results showed that the Ni-based tungsten carbide cladding layer had no pores and cracks and that their microstructural composition remained unchanged with CeO2 in the powder. After adding CeO2 into the powder, Ce atoms were absorbed on the surface of tungsten carbide particles to promote their dissolution and spheroidization. The preferentially formed high-melting-point Ce2O3 acted as a nucleating agent to induce the formation and dispersion of carbides. The shape of carbide particles changed from an irregular shape to a spherical shape. When the content of CeO2 was less than 0.2 wt.%, with the increase of CeO2 additions, the microstructure was refined. Meanwhile, the hardness and wear resistance of Ni-based tungsten carbide cladding layer increased. When the content of CeO2 was 0.2 wt.%, the refinement effect of CeO2 on the microstructure reached an optimum value, and the hardness value reached the maximum of 1139 HV10. Moreover the wear resistance was the best. This was attributed to the dispersion strengthening of undissolved tungsten carbide particles, the solid solution strengthening of Ni-based solid solution, and the precipitation strengthening of carbides. However, as the content of CeO2 exceeded 0.2 wt.%, excessive CeO2 increased the viscosity of the solution, resulting in component segregation. Thus, the refinement and spheroidization action of CeO2 weakened, and irregular-shaped carbides appeared again. The hardness and wear resistance of the Ni-based tungsten carbide cladding layer obviously decreased. Ce-containing Ni-based tungsten carbide layer can be widely used in deep-sea mining and other fields due to its high hardness and wear resistance.