Plasma Sprayed Tungsten Coating

Tungsten has the advantages of high melting point, high strength, high hardness and high wear resistance. In addition, it has low thermal expansion coefficient, good corrosion resistance and oxidation resistance, and good conductivity and thermal conductivity. Therefore, tungsten has been widely used in cutting-edge scientific fields, national defense industry and civil industry.

The wear resistance, high temperature resistance and corrosion resistance of tungsten coatings can be greatly improved by using tungsten as the surface wear-resistant protective coating for industrial parts. At present, chemical vapor deposition, physical vapor deposition and plasma spraying are the main methods to prepare tungsten coatings. Compared with chemical vapor deposition technology and physical vapor deposition technology, plasma spraying technology has unique advantages: easy to operate, high deposition efficiency, easy to prepare thick coatings, and easy to repair damaged coatings in situ. Therefore, Tungsten Coatings Prepared by plasma spraying technology as wear resistant and high temperature resistant coatings have attracted extensive attention in fusion reactor for plasma-oriented materials.

In the selection of coating materials, nano-materials have unique structure and excellent performance, which can greatly improve the service performance of the machine parts. The results show that the finer the tungsten powder, the higher the tensile strength, yield limit, corrosion resistance, high temperature resistance and contact fatigue resistance of the coating. Therefore, fine-grained Tungsten Coatings with high performance were obtained by atmospheric plasma spraying using nano-tungsten powder as raw material.

Taking 16 micron tungsten powder as spraying raw material to prepare tungsten coating as an example, using 40mm *8mm oxygen-free copper wafer as spraying base, after sandblasting pretreatment, and then cleaning with alcohol or acetone, a clean and rough surface can be obtained. After drying tungsten powder with a fineness of 16 um at 100 ℃ for 30 minutes, it was sprayed on the oxygen-free copper substrate by atmospheric plasma spraying technology. The power of the atmospheric plasma spraying equipment was 35KW, and the powder feeding method was internal powder feeding. The arc voltage is 70V, the arc current is 500A, the main gas is argon, the auxiliary gas is hydrogen, the flow rate of argon is 45L/min, the flow rate of hydrogen is 6L/min, the powder feeding rate is 25g/min, the spraying distance is about 120mm, the thickness of the coating is 1mm, the porosity of the coating sample is 4.5%, and the microhardness is 276.80HV. The bonding strength of the coating is 27 MPa.

The fine grain tungsten coating was prepared by plasma spraying with protective gas curtain in the process of granulation of ultrafine tungsten powder. The fine-grained tungsten and molybdenum coatings have low porosity, good mechanical properties and thermal shock resistance. They are suitable for wear-resistant surface protection layer of mechanical parts and high temperature plasma erosion parts, such as the first wall materials of nuclear fusion devices.

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