The effect of injecting transverse electrical current on indentation fracture, friction and wear of WC-Co alloy

The effect of electric current flowing parallel to the surface of a WC based hard alloy on its hardness and crack propagation with Vickers, Rockwell and Knoop indenters, abrasion and grinding were studied. Scratch tests were performed with a Rockwell diamond indenter at loads of L=1.5 and 3.5 N and a sliding velocity of v=0.2 mm/s during 100 cycles. Grinding was studied with a! 125 mm wheel diameter rotated at 2000 revolutions per minute. Currents with densities. J=0-85 A/cm(2) d.c. were injected parallel to the long aids of the sample. It was found that with the passage of electric current, the microhardness of surface layers decreased from 17.1 to 15.6 GPa. The average crack length, both parallel and perpendicular to the direction of the electric current, increased up to a maximum for the same range of J. However, the length of cracks parallel to the direction of electric current was a factor of similar to 1.3 greater than the perpendicular cracks.' The passing of current led to the agglomeration and compaction of the fractured carbides with formation of thick tribofilms. The steady state of friction is associated with the fracture of carbides, formation and delamination of tribofilms. It was found that the injection of the electric current increased the friction coefficient and wear rate of the WC-Co alloy.