2.45 GHz microwave plasma system for high-velocity thermal spraying

This research program investigates the use of microwave plasma, at 2.45 GHz frequency, to preheat nitrogen gas/coating powders when using a high-velocity spray technique. The heating process of this novel technique is obtained by the combination of dielectric and microwave plasma heating by using a long interaction cavity. As a result the thermal efficiency of the process will be as high as 50% compared with the present commercial plasma heated device which is in the order of 5% enabling temperatures of 1000 °C to be obtained. This paper presents the novel design and construction of a cost-effective microwave plasma system for thermal spraying. In addition, the preliminary result of an optical fibre temperature sensor operating in harsh microwave environment will be described.