Method of and apparatus providing oxide reduction in a plasma environment
US4689468A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 10, 1986 |
| Grant date | Aug 25, 1987 |
| Priority date | — |
| Expiry date | Feb 10, 2006 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC23C4/137
- WIPO fieldSurface technology, coating
- WIPO sectorChemistry
Abstract
In a plasma spraying system in which a main plasma gun electrically coupled to a workpiece or target and equipped with apparatus for introducing a spray powder therein provides a plasma stream to the target at high temperatures and supersonic speeds with an accompanying transfer arc between the main plasma gun and the target in a given polarity relative to the target, apparatus is present for simultaneously providing a second transfer arc at the target which has an opposite polarity relative to the target from the polarity of the transfer arc provided by the main plasma gun. The second transfer arc which is provided by a separate second or clean-up plasma gun electrically coupled to the target acts to reduce oxides at the target during melting of the target, spraying of the target with metallic powders and other plasma operations. The transfer arcs are provided by the main and clean-up plasma guns in conjunction with direct current power supplies coupled between the target and the guns so as to render the target positive with respect to one of the plasma guns and negative with respect to the other plasma gun. Additional direct current power supplies coupled to the main and clean-up…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.