Development of high power hybrid plasma spraying

This study is aimed at developing a high power hybrid plasma spraying devic e with a maximum radio frequency input power of 300 kW, in order to improve the strength and adhesion strength of sprayed coating. The stability of pl asma, energy efficiency, and melting state of particles were investigated u nder several conditions, and then characterization of coating was carried o ut. The stability of plasma condition is strongly influenced by gas flow ra te of Ar, N-2, and H-2 mixture against the power supplied. The energy effic iency of equipment is approximately 14%. The energy is lost mainly by joule 's heat in the oscillator circuit. Using this device, the maximum particle diameter for full melting is approximately 250 mu m. In the plasmas praying by not fully melted particles, the strength of coating decreases with incr easing particle diameter because of increased porosity size. On the other h and, in the spraying by fully melted particles, it is found that the high s trength of coating and the high adhesion strength at the interface between substrate and coating is obtained at large diameter particles. This tendenc y is explained by easy remelting or sintering at the interface between larg e particles. Actually, our experiment demonstrates that the maximum strengt h of coating and adhesion strength is more than 1300 and 250 MPa respective ly, by using fully melted particles with maximum diameter.