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

NiZr₂–ZrSi–Zr₅(Si_xNi_1−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(Si_xNi_1−x)₄ and during the growth of Zr₅(Si_xNi_1−x)₄, the consumption of Zr atoms at the lateral interface of liquid/Zr₅(Si_xNi_1−x)₄ resulted into developing Zr-poor zone near Zr₅(Si_xNi_1−x)₄. The microhardness and wear resistance of the coating were significantly improved by various reinforced phases in comparison to zirconium substrate. - Highlights: • NiZr₂–ZrSi–Zr₅(Si_xNi_1−x)₄-ZrC compostie coating was in-situ synthesized. • Ni–Si clusters transforming resulted into developing Zr-poor zone near Zr₅(Si_xNi_1−x)₄. • Reinforced phases significantly improve wear resistance of the coating