Tribological assessment of coated piston ring-cylinder liner contacts under bio-oil lubricated conditions

To alleviate high friction and corrosive wear in piston ring and cylinder liner friction pairs lubricated with bio-oil, four kinds of coatings: Ni-P, Ni-P-MoS2, Ni-P-GO and Ni-P-MoS2-GO have been prepared via chemical nickel plating technology. A multi-functional engine piston ring-cylinder liner tribometer was employed to evaluate their tribological behaviors. Furthermore, the changes of the bio-oil under different frictional conditions were analyzed by Fourier transform infrared spectroscopy. The results show that adhesive wear, scratching, spalling and mild wear took place respectively on the worn surfaces of piston rings with Ni-P, Ni-P-MoS2, Ni-P-GO, and Ni-P-MoS2-GO coatings. Ni-P-MoS2-GO coated piston rings showed excellent friction-reducing and anti-wear performance and subsequently have great potential for accelerating the application of bio-oil in IC engines.