Preparation, microstructural evolution and properties of Ni–Zr intermetallic/Zr–Si ceramic reinforced composite coatings on zirconium alloy by laser cladding

Abstract

NiZr2–ZrSi–Zr5(SixNi1−x)4-ZrC intermetallic/ceramic reinforced composite coatings were in situ synthesized by laser cladding the pre-placed Ni–Cr–B–Si powder on zirconium substrate. Microstructure and phase constituents were investigated by X-ray diffraction (XRD), optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Microhardness tester and block-on-ring wear tester were employed to measure the hardness distribution and wear resistance of the intermetallic/ceramic reinforced composite coating. Results indicated that the multiphase of reinforcements includes Ni–Zr intermetallic compounds (e.g., NiZr and NiZr2) and Zr–Si(C) ceramic phases (e.g., ZiSi, Zr5Si4 and ZrC). Ni–Si clusters transforming to Zr–Si–Ni clusters at high temperature facilitated the forming of Zr5(SixNi1−x)4 and during the growth of Zr5(SixNi1−x)4, the consumption of Zr atoms at the lateral interface of liquid/Zr5(SixNi1−x)4 resulted into developing Zr-poor zone near Zr5(SixNi1−x)4. The microhardness and wear resistance of the coating were significantly improved by various reinforced phases in comparison to zirconium substrate.