Effect of reciprocating sliding speed on the tribological performance of nano SiC(p) reinforced Ni-metal matrix composites produced by electrocodeposition.

In the present work, Ni/SiC metal matrix composite (MMC) coatings were prepared from a modified Watt's type electrolyte containing nano-SiC particles by direct current (DC) plating method to increase wear resistance of the electro co-deposited Ni. SiC nano particles with average particle size of 0, 1-1 microm were co-deposited with nickel matrix on the steel substrates. For this purpose, several studies were carried out to optimize deposition parameters for specific applications. The depositions were controlled to obtain the specific thickness (between 175-200 microm) and particle volume fraction in the matrix (between 0.03 and 0.10). The hardness of the resultant coatings was measured and found to be 280-571 HV depending on the particle concentration in the electrolyte and therefore, particle volume in the Ni matrix. The tribological tests were performed by a reciprocating ball-on disk apparatus sliding against M50 steel ball (Ø10 mm). All the friction and wear tests were performed under the unlubricated conditions at room temperature and in the ambient air (relative humidity 55-65%). The wear tests were carried out at different sliding velocities of 50 mm/s, 100 mm/s and 150 mm/s by using a constant dead load of 1.0 N. It was detected that increasing sliding speed resulted to increase wear rate but decreasing friction coefficient due to change in wear mechanism. Increasing sliding speed showed formation of tribo induced oxides up to 20 g/l SiC(p) in the electrolyte and wear mechanism was controlled by temperature induced fatigue wear. Further increase in the SiC(p) in the electrolyte caused an abrasive type of the wear.