Microstructural characteristics of laser cladding Ni60A/Ni-WC gradient coating on high Al-Zn sinking roller

Abstract

In order to improve the service life of high Al-Zn sinking rollers, four layer WC particles reinforced Ni-based alloy gradient coatings of Ni60A, Ni60A+10% Ni-WC, Ni60A+20% Ni-WC, Ni60A+30% Ni-WC were prepared on the surface of the sinking roller using coaxial powder feeding laser cladding technology. The microstructure and phase composition of the Ni60A/Ni-WC gradient coatings were studied using optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The results show that the microstructure of each gradient layer is composed of γ-Ni dendrite, multicomponent eutectic structure and reinforced phase of dispersed distribution. The number of reinforced phases gradually increases and the number of dendrites gradually decreases in the gradient coating from bottom to top. The main generated phases in Ni60A/Ni-WC gradient coatings are γ-Ni dendrite; eutectic composition of γ-Ni with Ni3B, Ni3Si, etc; reinforced phases of M6C, M7C3, M23C6, CrB, etc. Due to the gradient distribution of the original WC content and the dissolution of WC particles, the types of reinforced phases in the gradient coating also show a hierarchical distribution.