The influence of glassy carbon on tribological properties in metal - ceramic composites with skeleton reinforcement

This paper presents a results of mechanical and tribological properties of aluminum based composites with skeleton reinforcement. The aluminum alloy based composites were produced using pressure infiltration process. As a reinforcement ceramic foam with opened cells was applied. This reinforcement structure give an opportunity to limit the most common defects (like agglomeration, inhomogeneity, ect.) occurring in composite materials obtained by casting. In presented research three different types of porous foam were analysed. There were alumina foam covered by thin glassy carbon layer (Al₂O₃ - GC) and two types of glassy carbon foams (GC). Due to application of porous ceramic foam, an increasing of composite mechanical properties are expected. An additional glassy carbon layer with thickness up to 5 μm was applied for increasing a thermal conductivity and rapid heat dissipation from the material. Moreover, the skeleton structure of glassy carbon, and its wear mechanism, should decrease a friction coefficient value. Two manufactured types of composites: Al₂O₃ - GC foam and own produced glassy carbon foam were compared with material reinforced by spatial carbon structure obtained from commercial RVC (produced by Reynolds) foam. The results showed that the application of porous ceramic and ceramic - carbon reinforcement skeletons led to increasing of mechanical properties of composite. The conducted research using pin-on-disc method, with 2,5 MPa of load and 1,0 m/s of speed revealed that glassy carbon have significant influence on decreasing friction coefficient and wear rate. An analysis of material external layer in areas after coupling with pin (wear track) indicated a fragmentation of glassy carbon foam. The wear products are not remove from friction surfaces, but these products create thin carbon film with lubricant properties. The conducted research showed both, a possibility to produce composites with skeleton structure of reinforcement and a possibility of correction of material tribological properties using glassy carbon.