Development and tribological characterization of fly ash reinforced iron based functionally gradient friction materials

Abstract

The tribological and thermal properties enable iron based sintered materials with hard phase ceramic reinforcements as promising friction material for heavy-duty wind turbines. In wind turbines, the braking system consists of aerodynamic and mechanical braking systems. During application of mechanical brakes, the friction materials are pressed against the rotating low-speed shaft. The desired braking efficiency is achieved by utilizing a number of friction materials, which in turn are joined in a steel backing plate. Though this arrangement increases the braking efficiency, the hard phase ceramic reinforcement particles reduces the bonding strength between the friction material and steel backing plate. The joint failure leads to catastrophic failure of wind turbine. Hence, development of functionally gradient friction materials with wear resistance (contact surface) and joint strength (interface) is the need of the hour. This study attempts to fabricate and characterize the friction material with gradient composition profile along the cross section to enable functionally gradient property. Functionally gradient friction material is synthesized by gradient deposition of Fe, Cu, Cg, SiC and fly ash powders, which is followed by compaction and sintering. The fabricated functionally gradient friction material was characterized for microstructure and microhardness. The tribological performance (wear rate and coefficient of friction) of the developed functionally gradient friction material was investigated at various loads. The predominant wear mechanism was deduced from the worn surface morphology.Article history: (11pt, bold italic)ReceivedReceived in revised formAccepted The tribological and thermal properties enable iron based sintered materials with hard phase ceramic reinforcements as promising friction material for heavy-duty wind turbines. In wind turbines, the braking system consists of aerodynamic and mechanical braking systems. During application of mechanical brakes, the friction materials are pressed against the rotating low-speed shaft. The desired braking efficiency is achieved by utilizing a number of friction materials, which in turn are joined in a steel backing plate. Though this arrangement increases the braking efficiency, the hard phase ceramic reinforcement particles reduces the bonding strength between the friction material and steel backing plate. The joint failure leads to catastrophic failure of wind turbine. Hence, development of functionally gradient friction materials with wear resistance (contact surface) and joint strength (interface) is the need of the hour. This study attempts to fabricate and characterize the friction material with gradient composition profile along the cross section to enable functionally gradient property. Functionally gradient friction material is synthesized by gradient deposition of Fe, Cu, Cg, SiC and fly ash powders, which is followed by compaction and sintering. The fabricated functionally gradient friction material was characterized for microstructure and microhardness. The tribological performance (wear rate and coefficient of friction) of the developed functionally gradient friction material was investigated at various loads. The predominant wear mechanism was deduced from the worn surface morphology.Keywords: Friction materials, FGM, Powder metallurgy, tribology