Abstract
In contrast with the atmosphere plasma spraying (APS), the very low pressure plasma spraying (VLPPS) shows lower ability for heating spray materials at the plasma free region exit of nozzle. Most very low pressure plasma spraying at the present usually use a high power plasma gun which operated at great arc currents up to 2500A to meet lower ability for heating materials, thus result in a series of problems not only for the plasma torch but also for associated facility. According to the plasma spray characteristic in the low pressure environment we designed a plasma torch with separating anode and nozzle, and the powder injected to the plasma jets is from inside nozzle intake. In this study, the pressures in the plasma gases intake, nozzle intake and out of the plasma torch were measured respectively. For the practice, SUS 316 stainless steel coatings were prepared at plasma currents of 500-600A and arc voltage of 50V and the chamber pressure of 1000 Pa, the results indicated that the coatings with the equiaxed microstructure could deposited in the appropriate conditions.
