Plasma Spraying Of Molybdenum And Its Alloys Technology,

Plasma arc spraying which can apply to bigger work pieces to obtain thick coating has wide range of materials and high productivity than other surface techniques. People get the nice techniques of plasma arc spraying from the process of practice. In this thesis, various technique processes of spraying Mo and Mo-alloys by special equipments were carefully investigated. Four aspects were mainly analyzed. The relationship between work gas and plasma arc spraying, the spraying power and processes and coating characteristics, the flux of Mo powder and final coating characteristics at the same power, and the oxidation behavior of Mo powder and spraying power by analyzing the structure of coating with X-ray diffraction technique. The major conclusions are as follows:1. The equipments of plasma arc spraying can not work normally when use a flux of work gas less than 20L/min. The plasma arc blaze will be cooled down and the deposit speed will reduce when use a excessive flux of work gas. The appropriate flux should be maintained around 30L/min.2. It will cause the coating a excessive temperature if we use a small enough flux of Mo powder. Considering the influence of spraying power, we choice the adequate flux of 8g/min of Mo powder. To advance the spraying power will increase the deposit rate of powder when use the appropriate powder flux. But the Mo powder will be oxidized and the coating capabilities (such as compactibility and hardness) will descend when spraying power is excessive. The perfect spraying power is about 30kw.3. Mo powder will be oxidized at different degree in spraying process by X-ray diffraction analysis. And high hardness Mo-oxide which is formed at Mo substrate will improve the hardness and wearable ability of the coating.