Thermal sprayed ceramic coatings are well used as the electrode of corona discharge treatment in order to modify the surface of many kinds of films and papers due to its superior durability and adaptability. Some kinds of Al 2 O 3 -TiO 2 were sprayed by APS on the parallel plate electrodes, and output power of corona discharge generated by the electrodes was measured by using Sawyer-Tower circuit. In addition, discharge output power was calculated with an equivalent circuit of corona discharge. By comparing them, effects of the electrical property of the coating on discharge was researched. As a result, the electrostatic capacitance of the coatings influences the impedance of the whole circuit, and higher relative permittivity of the coating brought higher output power in a constant voltage.

In plasma spraying, generally, powders are radially injected into plasma jet. However, percentage of particles which have enough enthalpy to melt is not high in radial injection, possibly leading to low deposit efficiency especially for high melting point powders. In this research, powder port for radial injection was attached to an axial injection plasma torch in order to compare the plasma flame in both cases of axial and radial powder injections. The powder trajectory and the shape of the plasma plume were observed, and particle flux density, temperature, velocity, and deposit efficiency of alumina powders were measured and the results were compared between the two powder injection methods.

In order to utilize the blasting process for preparing surfaces of precision products, the factors affecting the work piece distortion and the degree of the distortion were investigated. The long and flat shaped specimens of the different materials and the thickness were blasted, and the phenomena induced by the blasting were investigated. In the result, almost the linear relationship between the surface roughness and the maximum deflection existed. In addition, the equivalent load was applied to the simple model of the distortion, and the correlative expression among the maximum deflection, the specimen's size, and the equivalent load was deduced. The results made it possible to select and design beforehand the products, and to optimize the blasting condition.