Pre-treatment on metal surface for plasma spray with cathode spots of low pressure arc

The cathode spots of the low pressure arc can remove the oxide layer and evaporate impurities on the metal surface. The removal of the oxide layer by using the cathode spots is expected to solve the recent problems of the chemical and mechanical cleaning methods. The phenomena of the cathode spots for pre-treatment of Atmospheric Pressure Plasma Spray (APPS) have been investigated. In this paper, the surface shapes of oxide and non-oxide work pieces were treated by using a composite pre-treating method: the cathode spots after grid blasting. In addition, they are compared with conventional cathode spots treated and mechanical blasted surfaces. As the results, the roughness on the surface of work pieces is arisen with the initial oxide layer thickness. It reveals the factors dominating bonding strength on the surface pre-treated by using the cathode spots of the low pressure arc. The bonding strength increases with the arithmetical mean height of the surface roughness due to the initial oxide layer thickness. The bonding strength is raised when the mean spacing of profile irregularities becomes narrow. The bonding adhesive strength treated by the cathode spots after the grid blasting is over 90 MPa.