Effect of transverse current injection on the tribological properties of WC cemented carbide

The effect of an electric current on the tribological properties of WC cemented carbide were studied. Cemented carbide bars having a composition of 90% WC, 8% Co, 1.8% TaC, 0.2% NbC with dimensions of 5×6.5×20 mm were mounted in a sclerometer. A d.c. current with densities in the range of 0–90°A/cm2 was injected parallel to the long axis of the bar during the test. The surfaces were examined by scanning electron microscopy, and by X-ray photoelectron spectroscopy. To measure wear and friction, an indenter with loads of 1.5 and 3.5 N was drawn over the surface of the test sample with a controlled velocity of 0.2 mm/s for 100 cycles. It was found that the scratching process fractured the carbide grains. The fractured carbides were agglomerated and compacted, forming a thick tribo film. Tungsten oxide WO3 was found in the scratch track after scratching with current injection. With the injected current of 90 A/cm2 the track width increased by a factor of 1.4 and 3 and the friction coefficient increased by a factor of 1.5 and 2 with a load of 1.5 and 3.5 N, respectively, as compared to scratching without a current.