Corrosion resistance of pressure/pressureless sintered cemented carbides with/without graphene oxide in NaOH solution

The electrochemical corrosion performance of WC-Co hard alloy was studied under pressure/pressureless sintering and conditions with/without graphene oxide added. Three electrochemical testing methods were used to evaluate the corrosion behavior: open circuit potential, electrochemical impedance spectroscopy, and dynamic potential polarization. The corrosion resistance of the alloy was compared using three parameters of corrosion potential, corrosion current density, and total impedance. The corrosion mechanism was studied by observing the surface morphology of corroded alloy using scanning electron microscopy and analyzing the surface corrosion products using X-ray photoelectron spectroscopy. The results showed that pseudo-passivation phenomenon appeared in the potentiodynamic polarization curve of the hard alloy in the sodium hydroxide solution. The corrosion behavior was mainly controlled by anodic dissolution, with the dissolution of WC phase being greater than that of Co phase. The corrosion resistant properties of the pressure sintered cemented carbide are higher than that of the pressure-less sintered cemented carbide respectively in NaOH solution, mainly because pressure increases the grain size and decreases the grain boundaries of cemented carbide, which can be regarded as the dislocation wall between grains and normally attacked by the serious corrosion preferentially.