Jiansong Zhou

Friction and wear behavior of laser cladding Ni/hBN self-lubricating composite coating

NiAl/hBN coating was successfully prepared on a Ni-based superalloy substrate by means of laser cladding. The microhardness profile of the composite coating along the depth direction was measured, while its cross-sectional microstructures and phase compositions were analyzed by means of scanning electron microscopy and X-ray diffraction. Moreover, the friction and wear behavior of the composite coatings sliding against Si3N4 from ambient to 1000 °C was evaluated using a ball-on-disc friction and wear tester, and the worn surface morphologies of the composite coatings were observed using a scanning electron microscope. It was found that the laser cladding NiAl/hBN coating on the Ni-based superalloy substrate had high microhardness and good friction-reducing and antiwear abilities at elevated temperatures up to 1000 °C. The friction and wear behavior of the laser cladding NiAl/hBN coating was strongly dependent on test temperatures. The coating had a small friction coefficient and wear rate as it slid against the ceramic counterpart at elevated temperatures up to 1000 °C. The wear mechanism was characterized by mixed adhesion and abrasive wear as it slid against the ceramic ball below 300 °C and mild adhesion wear and plastic deformation up to 400 °C and above.

Effect of ZrB2 on the Microstructure and Wear Resistance of Ni-Based Composite Coating Produced on Pure Ti by Laser Cladding

ZrB2-reinforced Ni-based composite coating was fabricated on pure Ti substrate by laser cladding. The effect of ZrB2 doping on the microstructure and tribological properties of conventional NiCrBSi composite coating was investigated. It was found that the microhardness and wear resistance of pure Ti substrate are greatly improved after laser cladding. It is remarkable that the ZrB2 phase could further enhance the conventional NiCrBSi coating and generate higher hardness. During friction, due to the ceramic nature of ZrB2, that is, ultra-high melting point and hardness, the adhesive wear could be alleviated that occurs in conventional Ni-based coating, resulting in a better wear resistance. Thus, it is concluded that the incorporation of a ZrB2 phase is an effective and attainable way to improve the tribological properties of conventional Ni-based composite coatings.