Volume 41, Issue 1 (January 2013)
Functionally Graded Bronze/Tungsten-Carbide Castings: A Characterization and Property Study
The contact resistance and wear behavior of electrical contact surfaces is a function of hardness, applied load, and material constituents. This work presents a characterization of the mechanical and physical properties of conducting alloys fabricated as functionally graded metal matrix composites (MMCs), in particular, tungsten-carbide-filled bronze. Tungsten-carbide reinforcing particles are attractive in this application for their high hardness and concomitant wear resistance. When used as bushings, bearings, and sleeve materials, bronze has improved wear performance with the addition of tungsten-carbide particles, which improves the hardness of the contact surface. Bronze might also be attractive as a potential electrical conductor when a need exists for high-strength, wear-resistant contact surfaces as found in circuit breakers and sliding electrical contacts. An overview of two types of MMC production methods, sedimentation and centrifugal casting, is presented. MMCs fabricated using the two different methods are compared and contrasted based on physical and mechanical properties. The use of centrifugal casting provides a more effective improvement in physical and mechanical properties plus significant improvement in hardness with relatively low reduction in base-material conductivity was observed. The centrifugal casting method allows for a more tailored product in terms of locating enhanced material properties within the casting.