Ni-WC composite coatings by carburizing electrodeposited amorphous and nanocrystalline Ni-W alloys

In situ formation of tungsten carbide in the matrix of FCC nickel has been achieved by carburizing of the electrodeposited Ni-W alloy coatings. The size of the carbide particles ranges between 100 and 500 nm. The carbide phase is also present in the form of very small precipitates inside the nickel grains. The size of such precipitates is between 10 and 40 nm. The carburizing environment was created by introducing a flowing mixture of vaporized 95.5% alcohol (0.25 ml/min, liquid) and argon (0.5 L/min, gas) into the carburizing furnace. Supersaturated nature of electrodeposited amorphous and nanocrystalline alloys, in addition to high diffusivity, have been attributed for the formation of carbide phase in the deposits at a temperature range of 700-850 deg. C. The carbide-metal interface is clean and the composite coatings are compact. Hardness values up to about 1100 KHN are achieved. Hardness increases with tungsten content and carburizing temperature.