Study On Preparation And Properties Of Plasma A Facing Materials Tungsten Coatings Used In Fusion

Ordinary tungsten powder was spheroidized by different types of atmosphere plasma spraying machine with water cooling system. The influence of power to properties of tungsten powder was studied. The results indicate that the tungsten powder has a high degree of spherical. When the power is low, the tungsten powder has high recycle rate, low oxygen content, high flowability; however, when the power is high, the tungsten powder has a low recycle rate, high oxygen content, poor flowability. Under the same process conditions, the powder by different atmosphere plasma spraying machine have different characteristics. Furthermore, the device of SULZER Metco-7MC has good performances to prepare spherical tungsten powder. When tungsten was spheroidied by7MC at25KW, its flowability is5.9s/50g, oxygen content is0.095/wt%. The tungsten coating with spherical powders has higher density, bond strength, etc than using normal powders. Besiedes, different graded interlayers are used in coating, compared the coating without graded interlayers, the form coating have high bond strength and density, etc.Results of optical microscopy, scanning electron microscopy, AFM are presented for tungsten and W-Ni-Fe coating produced by low and high cold gas dynamic spraying, respectively. With size D502and7μm, spraying distance10～15mm, high properties coatings without obvious oxide can be compared. The critical velocity of tungsten powder was calculated, what is more, tungsten particles collision was also simulated by soft ANSYS/LS-DYNA. Cold gas dynamic spray (CGDS) is a rapidly developing coating technology, in which spraying particle is deposited through plastic impact on s substrate at high velocities at low temperature. In these experiments, the process produced a reasonably dense tungsten coating and tungsten alloy coating. This paper reports the effect of deposition parameters which including temperature, spraying distance, particle size, etc. on the structures formed.The tungsten membranes with ultra microstructure on CuCrZr alloy and CLAM substrates have been prepared using remaked cold-wall reactor, metal organic chemical vapor deposition (MOCVD). The membranes were produced by pyrolysing the tungsten hexacarbonyl in low pressure, at air and argon atmosphere. When formed at or below600℃, they were poorly crystalline. Besides, the membranes had low properties including thickness, density, bonding performance with substrate and so on. While above this temperature, the properties of tungsten membranes had been greatly improved, and all the membranes consist of tungsten in the β-W. Then annealed at700～800℃, β-W will be converted into a-W. As in other variations of the pyrolysis, oxygen is observed, although these reduce with increasing temperature of deposition. In addition, when filled with argon, the oxygen content will also reduce. Moreover, these membranes have stable chemical composition and microstructure. The bonding properties and polish of surface could be enhanced greatly. The coating on CuCrZr alloy has better properties than CLAM.