Tribology International 40 (2007) 1217–1224 Development of fly ash-based automotive brake lining Samrat Mohanty à , Y.P. Chugh Mining and Mineral Resources Engineering, College of Engineering, Southern Illinois University Carbondale, IL 62901, USA Received 15 May 2006; received in revised form 13 September 2006; accepted 7 January 2007 Available online 23 February 2007 Abstract Coal-fired power plants all over the world generate huge amounts of fly ash each year, 70 million tons of which are produced in the United States alone. Only 40% of all fly ashes generated in the USA find beneficial applications and rest have to be disposed off, which is burden for the generation industry. Fly ash particles possess certain characteristics that make them suitable for use in friction composites as a filler material. An attempt has been made through this research to incorporate more than 50 wt% of fly ash particles in automotive brake lining friction composites. This paper presents the research carried out on development of friction composites, using fly ash obtained from a specific power plant in Illinois. Ingredients such as phenolic resin, aramid pulp, glass fiber, potassium titanate, graphite, aluminum fiber and copper powder were used in the composite development phase, in addition to the fly ash. The developed brake lining composites have exhibited consistent coefficients of friction in the range of 0.35–0.4, and wear rates lower than 12 wt%. Published by Elsevier Ltd. Keywords: Fly ash; Filler; Brake lining; FAST; SEM 1. Introduction 1.1. Background: automotive brake lining composite Brakes are one of the most important safety and perfor- mance components in automobiles. Most of the brake linings used in American cars are based on a metal fiber reinforced phenolic resin matrix and are called semi- metallic. There are, however, also other types of lining materials, categorized into metallic, organic and carbon- based. Most of the brake linings are typically a composite of a number of different materials. Sometimes, up to 20 or 25 different constituents are used. These ingredients are categorized into four broad classes: binders, structural materials, fillers and frictional additives/modifiers. The binders bind together rest of the ingredients, structural materials provide the structural reinforcement to the composite matrix, fillers make up the volume of the brake lining, while keeping the costs down, and friction modifiers stabilize the coefficient of friction [1]. The above constitu- ents are expected to perform synergistically in an optimized brake lining to provide a consistent friction and wear performance at varying operating conditions, should generate less noise and vibrations and should be low cost to manufacture. Before the ban on usage of asbestos in brake linings was imposed by United States Environmental Protection Agency in 1989, asbestos was the most preferred filler material. Asbestos had a few engineering characteristics that made it very desirable for inclusion in brake linings. Asbestos is thermally stable up to 500 1C, it helps regenerate friction surface during use, it insulates ther- mally, it is strong and flexible and, mostly, it is available cheap. Since the ban on asbestos, researchers have struggled to come up with an equally efficient alternative. Barites, mica and cashew dust are amongst some of the materials that have been considered for use as fillers [2]. 1.2. Fly ash as a brake lining ingredient Coal combustion byproducts are the inorganic residue left behind during the coal combustion process. Fly ash is one such byproduct. Disposal of fly ash is an environ- mental and economic liability for power plants across USA, as environmental regulations have to be adhered to ARTICLE IN PRESS www.elsevier.com/locate/triboint 0301-679X/$ - see front matter Published by Elsevier Ltd. doi:10.1016/j.triboint.2007.01.005 à Corresponding author. Tel.: +1 618 4534096. E-mail address: samrat@siu.edu (S. Mohanty).