Amorphous SiC coatings for WC cutting tools

Abstract

In this work, SiC films were deposited by r.f. magnetron sputtering onto WC and silicon substrates from a commercial sintered SiC target. After determining the influence of deposition parameters on the properties of the films deposited onto silicon substrates, suitable conditions were chosen to produce high quality 5 μm thick films on WC pieces. Mechanical characterization of the films was done by microhardness and residual stress measurements. High deposition rates (up to 40 nm/min), relatively low compressive residual stresses (<2 GPa) and high hardness (30 GPa) are obtained at high power levels (400 W), although a super hard material (⩾40 GPa) could be achieved at lower r.f. power (100 W). A ball–crater apparatus was used to perform both thickness measurements and wear resistance tests. The wear rates of the coated pieces were found to be reduced to less than half of the uncoated ones. Coated and uncoated pieces were submitted to vacuum and atmospheric thermal annealing. SiC coatings presented excellent thermal stability as no reduction of hardness was observed at temperatures up to 1100 °C. Annealing in air showed that SiC-coated WC pieces remained unaffected even at temperatures up to 700 °C.