High temperature properties of micro-crystalline WC-4Co alloys deposited on cast steel roll by electro-spark deposition

The ceramic cemented carbide WC-4Co alloy was deposited on the surface of cast steel roll by electrospark deposition (ESD) process. The high temperature wearresistance at 300 ℃ in air, and the microstructure, surface morphology and high temperature oxidation resistance at 800 ℃for 100 h in air of the coating were measured by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicate that the thickness of coating was 20~30 μm and the coating consisted of Fe3W3C, Co3W3C, Si2W and Fe2C phases. The coating had better high temperature wear resistance which was 3.4 times higher than that of the cast steel substrate at 300 ℃. The wear mechanism of the coating was adhesion wear, fatigue wear, oxidization wear and abrasive wear at 300 ℃. The thickness of dense oxide film was 10~20 μm for WC-4Co coating at 800 ℃ for 100 h in air and the primary phases in the continuous oxide scales of the coating contained Fe3O4, Fe2O3, W20O58 and Si. The oxidation kinetic curves of the oxide scales followed a similar linear law. The oxidation resistance of WC-4Co alloy coating was 2.6 times higher than that of the substrate. The changes in the oxide nature and fine microstructure played a critical role in increasing the high temperature wear resistance and high temperature oxidation resistance of the coating.