Microstructure of Electro-Spark Deposition WC Coating on BT20 Titanium Alloy

The WC coating was produced on the surface of BT20 titanium alloy in Ar atmosphere by electro-spark deposition technique using WC as electrode. The microstructures and the phase compositions of WC coatings were characterized by SEM, EDS and XRD. The microhardness distribution of the deposition coating was studied by microhardness tester. The results show that the coating consists of TiC, WC, W and W2C phases. TiC is a new phase formed by the reaction between the electrode material and the substrate which is the main phase of the deposited layer. The excellent metallurgical bonding between the coating and the substrate is obtained. The coating surface displays a "splash" shape. The nanometer crystallite stacking structure and a small amount of dendritic structure can be observed in the cross section morphology which reflects the electric spark deposition process for rapid heating and the cooling mechanism. The maximum microhardness of the coating is three times of that of the substrate.