HVOF sprayed tungsten carbide coating

       HVOF sprayed tungsten carbide coating





In tungsten carbide, carbon atoms are inserted into the gaps of the tungsten metal lattice, without destroying the original metal lattice, forming an interstitial solid solution, so it is also called an interstitial (or insertion) compound. Tungsten carbide can be prepared by heating a mixture of tungsten and carbon at high temperature, and the presence of hydrogen or hydrocarbons can accelerate the reaction. If prepared with oxygenated compounds of tungsten, the final product must be vacuum treated at 1500°C to remove carbon oxides. Tungsten carbide is suitable for machining at high temperature, and can be used to make cutting tools, structural materials of kilns, jet engines, gas turbines, nozzles, etc.

Another compound of tungsten and carbon is ditungsten carbide, the chemical formula is W2C, the melting point is 2860°C, the boiling point is 6000°C, and the relative density is 17.15. Its properties, preparation methods and uses are the same as those of tungsten carbide.

The experiment of laser cladding nano-WC powder on 2Crl3 stainless steel substrate was carried out by using a 7KW cross-flow CO2 laser. The microstructure and properties of the coatings were examined by scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectrometer (EDAX), and microhardness tester. The results show that a dense composite coating can be obtained by laser cladding nano-WC powder; the cladding area of the coating exhibits typical Fe cellular dendrites and Fe-CW structures between dendrites; XRD analysis shows that the composite coating The coating is mainly composed of several phases of Fe, WC, W2C and Fe3C; the performance test results of the coating show that the surface hardness is 1750HV. The average hardness of the cladding layer is 1200HV, and the wear resistance is 2.5 times higher than that of the matrix.

The valve is one of the main basic components with a large amount of consumption in the machinery industry. During the frequent opening and closing process of the valve, the sealing surface of the valve is scratched, and the factors such as corrosion, erosion and high temperature of the medium make the valve seal. Premature damage to the surface has become one of the causes of poor sealing and leakage.

Cobalt-based tungsten carbide alloy powder or nickel-based tungsten carbide alloy powder and chromium-based tungsten carbide alloy powder are sprayed with HVOF. The hardness can reach HV1200 and high temperature resistance of 850 degrees, so that valve parts are resistant to wear, corrosion, high temperature and oxidation. . More than manual surfacing, chroming, carburizing, quenching and tempering, and processes, the production efficiency can be increased by more than 2 times, the production cost can be reduced by more than 50%, and the service life can be extended dozens of times.

Examples of tungsten carbide coating sprayed parts: gate, valve seat, valve core, plunger, ball, flange, valve stem.