Effect of Graphite Content on the Tribological Behavior of a Cu-Fe-C Based Friction Material Sliding against FC30 Cast Iron

Abstract

Focus of the study has been placed on the effect of graphite content on tribological behavior of a Cu–Fe–C based friction material sliding against FC30 cast iron. Experimental results indicated that, after sintering in air, the densities of Cu–Fe–C specimens decreased, oxygen contents increased, and essentially all original metallic constituents turned into oxides. As graphite content increased, the amounts of Fe₂O₃, Cu₂O and Cu–Sn decreased, while CuO and FeSn₂ contents increased. The friction coefficient profiles of Cu–10%Steel wool–10%Al–10%Al₂O₃–10%Sn (vol%) material (C0) and Cu–10%Steel wool–10%C–10%Al–10%Al₂O₃–10%Sn (vol%) material (C10) are almost identical. After sliding for a few minutes, their friction coefficients start to decay. The friction coefficient of Cu–10%Steel wool–20%C–10%Al–10%Al₂O₃–10%Sn (vol%) material (C20) maintained to be high and stable throughout tests. The mass loss of C20 was larger than that of C0 or C10. The mass loss of FC30 sliding against C20 was smaller than that of FC30 sliding against C0 or C10. While both particulate and film types of debris were observed on each Cu–Fe–C specimen, more particulate debris was observed on C0 and C10 than on C20 surface. Chemical analysis of worn surfaces indicated that Fe was dominant on C0 and C10 surfaces, while large amounts of Fe and Cu were detected on the worn surfaces of both C20 and FC30.