Optimization and dry sliding wear behaviour of spray coated MoS2 on automotive ball joints through response surface methodology

Abstract

Ball joints used in steering linkages for load transfer generally provide articulation and rotation with degree of freedom. The function of the ball joints is to allow the suspension of the vehicle to move up and down, while at the same time it also allows the wheels to turn left or right. In order to increase the service life of the ball joints, manufacturers have resorted to various surface treatment and protective wear coatings. Wear on ball joint has been a perennial issue. Hence this investigation is focused to explore the possibility for wear reduction by spray pyrolysis technique employed on EN18 medium carbon steel coated with molybdenum disulphide as a strengthening agent. The adhesive bonding between the steel and coating was enriched by heat treating the coated material for 1 h at 400 °C, which not only improved the wear property but also increased the hardness. Wear studies were conducted using pin on disc instrument at ambient temperature in dry condition. By varying process parameters namely the load, velocity and sliding distance identified by Response Surface Methodology (RSM), optimum wear rate was calculated. The Analysis of Variance (ANOVA) technique was utilized to forecast the influencing parameter in sequence which identified load as a prime parameter on increasing the wear rate followed by sliding distance and velocity. Regression equation employed, enabled the validation of the experimental results with an error less than 5%. FESEM analysis revealed the homogeneous distribution of coated layer on the base metal. The optimum values of wear rate have been achieved at 15 N, 2.71 m s−1 and 750 m for desired industrial application. Investigations with FESEM and EDAX ensured the presence of hard MoS2 particles in the base metal. Studies through ANOVA technique have conveyed that the sliding distance has greater impact on the wear rate.