Indentation behaviour of superelastic hard carbon

Abstract

Superelastic hard carbon particles widely varying in structure and properties have been studied by instrumented microindentation technique. The carbon particles up to 200 μm in size were produced by fullerene collapse upon high-pressure high-temperature treatment of metal–fullerene powder mixture with simultaneous sintering of metal matrix composite materials (CM) reinforced by the particles. The structure and properties of the carbon particles were controlled by changing synthesis parameters and the state (composition and structure) of the parent fullerite crystals. The specific features of the instrumented indentation behaviour of the particles were studied as a function of their hardness. Mechanical properties of the particles tested at loads of up to 1970 mN exhibit an indentation size effect, which becomes more pronounced with increasing hardness of the carbon particles. Upon holding at a constant load, the fullerene-derived carbon particles undergo unrecoverable deformation, and the indentation creep CIT increases with increasing particle hardness. An increase in hardness of the reinforcing carbon particles substantially improves the wear resistance of the CM and decreases their friction coefficient.