Synthesis of Ni-WC/Al-Ni functionally graded coating with advanced corrosion and wear resistance on AZ91D Mg alloy by laser cladding

The low hardness and poor wear and corrosion resistance of Mg alloys restrict their further applications. Laser cladding technology has been employed to prepare coatings on metals and alloys, but owing to the low melting point of Mg alloy, it is difficult to clad high-performance coatings that usually have high melting points directly. To achieve superior corrosion and wear resistance, a Ni–WC/Al–Ni functionally graded coating was designed and prepared on AZ91D Mg alloy. The microstructure, hardness, corrosion resistance, and tribological behaviors of the coating were studied. The results showed that good metallurgical bonding was obtained between the coating layers and substrate. The Ni–WC top-layer had excellent mechanical performance, and corrosion and wear resistance. The wear resistance of the top-layer was 5–8 times that of the substrate and contributed to the simultaneous enhancement of hardness and corrosion resistance. The results suggest that the use of a functionally graded prepared coating is a good strategy to form a high-performance coating on Mg alloy.