Wear-resistant aluminum-boron-carbide cermets for automotive brake applications

Aluminum-boron-carbide (Al-B-C) brake pads were evaluated using the industry standard Friction Assessment and Screening Test (FAST). Variations in processing yielded samples with a range of mechanical properties and subsequent test behavior. Of these, successful samples were produced from coarse, bimodal B4C powders that were highly reacted with infiltrated aluminum. These particular materials exhibited wear rates more than an order of magnitude lower than current asbestos and semimetallic materials while producing no increase in rotor wear. The resulting friction coefficients fell within the industry standard range of 0.3 to 0.45 after break-in and did not change with temperature. Optical metallography, SEM and EDS analysis indicated that wear surfaces were coated with an iron-rich, two phase glazing, with one phase containing substantial amounts of aluminum. This interface glazing is believed to enhance performance through maintenance of smooth surfaces and increased pad to rotor contact. These results suggest that full scale and vehicle tests be conducted to determine actual performance. (C) 1999 Elsevier Science S.A. All rights reserved.