Ni-P SiC composite coatings on piston rings by plate and bumper technique and its tribological properties

Breakdown of piston rings in the automotive sector due to wear, corrosion and high temperatures is common. Conventional hard chrome and chrome ceramic coatings with hexavalent chromium possess environmental risks due to its carcinogenic effects. Nickel-phosphorus (Ni-P) plating is not hazardous and hence silicon carbide (SiC) uniformly distributed in Ni-P coating by plate and bumper method is made as an eco-friendly and cost-effective approach. This Ni-P SiC composite coating provides high hardness, wear resistance, corrosion resistance and improved friction resistance due to the uniform distribution of the SiC composite particles. The amorphous Ni-P coating is converted to nickel phosphide intermetallic crystalline form during the heat treatment at 300 °C and is confirmed by XRD. The heat treatment also increases the microhardness in the rage of 810 to 1015 HV for Ni-P SiC composite coating. This method significantly improved the mechanical properties of piston rings by ∼ 5 to 6%.