Optimization of Tribological Properties of Nonasbestos Brake Pad Material by Using Steel Wool

The gradual phasing out of typical brake pad material led to the spark of extensive research in development of alternatives. Henceforth we have performed a tribological study to improve the performance characteristics of the friction product (brake pad) by using steel wool, a metallic material which has an excellent structural reinforcement property and high thermal stability which are indeed required to improve the performance of the brake pad. Under the study, five frictional composites were developed and optimized using the same ingredients in an appropriate proportion except steel wool (0%, 4%, 8%, 12%, and 16%) which is compensated by synthetic barite, and the synthesized compositions are designated as Na01 to Na05. The developed pads are tested for tribological behaviour under conventional environment in a standard pin on disc tribometer. It is observed that increase in steel wool concentration resulted in high coefficient of friction and low wear rate of pad as resulted in Na05 composition. SEM analysis of the wear surface has proved to be useful in understanding the wear behaviour of the composites. 1. Introduction The core of the braking device is friction material, which is expected to continue its functioning reliably and efficiently for a prolonged time in adverse operating conditions [1]. Nonasbestos organic fiber reinforced metallic friction composites are increasingly being used in automotive brake disc pads, shoes, linings, blocks, clutch facings, and so forth, primarily because of awareness of health hazards of asbestos. These are essentially multi ingredient systems in order to achieve the desired amalgam of performance properties [2–5], and more than several hundred ingredients have been reported in the literature for being used to tailor the friction composites. These are classified into four major categories, namely, binder, structural modifiers, friction modifiers, and fillers, based on the major function they perform apart from controlling friction and wear performance. The influence of these ingredients on performance properties is so complex that formulation of friction materials is still referred as an art rather than science [2]. These friction materials have to satisfy safety-related features such as friction stability, resistance to fade, and ecofriendly nature. Nowadays, factors such as economics of operation, increased power to weight ratio, road development, and road traffic demand more efficient braking system which requires improved brake friction materials [6]. The use of asbestos fiber as reinforcement in the friction