Preparation of Tungsten - Copper Gradient Heat Sink Material by Plasma Spraying

Plasma spraying, also known as thermal spraying method, is the use of plasma arc generator will be introduced into the nozzle gas heating and ionization to form a high-temperature high-speed plasma jet, metallic or non-metallic materials are melted and atomized and sprayed at high speed onto the pre-treated workpiece surface to form a coating.

At present, there are 2 main directions in the preparation of W-Cu functionally graded materials by plasma spraying. One is to choose the Al-12Si, Ni- 20Al, Ti and other thermal expansion coefficients between W and Cu as the transition layer. The other is to select the W and Cu gradient layers as the transition layer. These two kinds of spraying methods have been successfully applied to industrial practice at present, especially second methods.

Foreign scholars used plasma spraying technology, Al-Si and Ni-Al and W as the transition layer, and successfully prepared the W-Cu gradient functionally material with the thickness of spray coating about 5 mm and the theoretical density of 92%. Chinese scholars sprayed a 200 um gradient layer on a Cu substrate, the W content of which gradually increased from 0 to 100% at an increasing rate of 20% (mass fraction). Finally, 200 um pure tungsten was sprayed on the surface of the gradient layer. The relative density of the sprayed layer was 92.5% .

Due to the high temperature of plasma flame, all kinds of spraying materials can be heated to molten state, so plasma sprayed materials can be widely used, and various performance sprayed coatings can also be obtained. It is especially suitable for refractory materials such as spraying ceramics. The process is stable and the quality of the coating is high. Besides, plasma spraying, like other spraying methods, is not restricted by the size of the parts. The matrix material is extensive, and the machining allowance is small. It can be used for spraying and strengthening the surface of common base parts.

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