Role of velocity discontinuity imparted by copper and nickel coatings of different thickness

Abstract

In mating pairs system, the pairs will have relative motion among themselves resulting in damage of contacting surfaces. During such relative motions friction and wear occurs. Extensive research has been carried out for identifying friction and wear effects. One of the important factors is found to be discontinuity in velocity at the interacting surfaces. This discontinuity in velocity was found to have a major role in affecting coefficient of friction and wear.In the present investigation to impart velocity discontinuity copper and nickel coatings of different thickness, were coated on mild steel pin. The copper coating was incorporated by thermal spray technique and nickel coating was carried by electroplating technique. Experiments have been conducted using pin on disc test rig with speed 500 rpm, load 30 newton and sliding time 30 seconds. The shear force was monitored in personal computer and coefficient of friction was estimated. Scanning electron micrograph (SEM) and Energy dispersive analysis X-ray (EDAX) was carried out. The coefficient of friction was found to be dependent on type of coating materials. Coefficient of friction was in the range of 0.51 to 0.52 for copper coating and 0.43 to 0.46 for nickel coating. The observed features in scanning electron micrograph attribute dependency of friction coefficient on coating thickness. The energy dispersive analysis X-ray study reveals no oxidation of copper, nickel and iron.