Preparation And Properties Of Re-W Coatings On Carbon Materials

Plasma facing materials is very important for fusion materials. In recent years, with the development of controlled nuclear fusion technology, tungsten as plasma facing components has got wide attention. Coating technology can solve the difficulty in molding and connection of tungsten so that carbon-based tungsten coatings materials are widely used by fusion scientists. In this paper, double glow plasma surface alloying technology is applied to study the metallization of carbon materials with pure rhenium plate and pure tungsten as plate source and high purity argon as working gas. The organization, structure, bonding strength and other properties of tunsten coatings is analyzed employing scanning electron microscope, energy dispersive X-ray spectrometre, X-ray diffraction, hardness measurement and scratch test, drawing the following conclusions:1. The size of tubular electrode has great influence on experimental process. When deep-well structure is adopted,Φ100mm×45mm stainless steel tipe is selected for tubular electrode.2. Rhenium coating is prepared on graphite substrate with electrode spacing of15mm, working pressure of35Pa, workpiece temperature of1200℃, source voltage of900～950V, workpiece voltage of550-600V and holding time of2h. Re coating has leveling surface with inhomogeneous particle and tidy section of13μm thickness. There occurs diffusion between rhenium coating and graphite matrix with diffusion layer thickness of1.5μm.3. The effect of electrode spacing, working pressure, workpiece temperature, source voltage, workpiece voltage and holding time on tungsten coating is studied. Coating grains become coarser and more uniform as workpiece temperature increases. The thickness of Re-W alloy layer has nonlinear relationship with temperature while sediment thickness is almost not affected by temperature. Electrode distance and woking pressure has great influence on deposition thickness and a little infuence on alloy layer thickness. Alloy layer and the deposition layer have parabola and linear relation with the holding time respectly. Electrode distance of20mm, pressure of35Pa, workpiece temperature of950℃, source voltage Vs=900～950V, workpiece voltage=550～600V and holding time of9h are good preparation parameters of tungsten coating.4. Semi-infinite model is employed to calculate and deduce interdiffusion of Re-W in double glow plasma surface alloying experiment with diffusion activation energy Q=156kJ·mol-1and diffusion constant Do=4.26×10-7cm2·s-1。...