Toughening of WC-Co Cemented Carbides by In-stiu Transformed Carbon Fiber

Abstract

Abstract WC-2Co cemented carbides toughened by in situ transformed carbon fibers were prepared by hot-press sintering at 1450°C using pre-oxidized polyacrylonitrilefibers (PANf) as the precursor. The phase composition, microstructure and mechanical properties of the samples with different added fractions of PANf were investigated. The results show that the PANf transformed in situ into carbon fibers at 1450°C during the hot-press sintering. The formed carbon fiber could supply carbon to the sintering system, suppressing the formation of η phase and improving the relative density of the samples. With the increase in the added fraction of PANf, the Vickers hardness of the samples initially increased and then slightly decreased, reaching its maximum of about 1900 HV10 with 0.5 wt.% PANf. The flexural strength and fracture toughness of the samples gradually increased from 530 MPa and 5.5 MPa·m1/2to 700 MPa and 7.5 MPa·m1/2with the increase in the added fraction of PANf from 0 to 2 wt.%. The toughening mechanisms were cracks deflection, fiber pull-out and crack bridging.