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Hardfacing by chemical vapor deposition of components used in coal gasification units.
Stephenson-JB; Soboroff-DM; McDonald-HO
Thin Solid Films 1977 Jan; 40(1):73-80
The Bureau of Mines, as part of an interagency agreement with Energy Research and Cevelopment Administration, is investigating the feasibility of hardfacing the critical surfaces of valves and similar devices by chemical vapor deposition. The objective is to increase the life of these components in the abrasive and erosive environment existing in coal gasification units. Various chemical vapor deposition materials such as refractory metals, carbides, and nitrides were considered for this application, and they are undergoing laboratory investigation and evaluation. Because of the Bureau's previous experience with tungsten in lining rocket nozzles, it was the first hardfacing material investigated. Laboratory research indicated that adherent tungsten coatings could not be obtained on the stainless and carbon steels used in valve construction unless they were first electroplated with a thin layer of nickel. Tungsten was deposited by hydrogen reduction of tungsten hexafluoride at temperatures ranging from 450 deg to 650 deg c. A large reaction chamber 20 inches (0.51 M) wide with a rotating gas- dispersion apparatus was fabricated. The large unit was used to coat carbon steel valve seats 10 inches (0.25 M) id with tungsten, and induction was used to heat the ball valve seats to reaction temperature. Successfully coated valve seats are undergoing evaluation in the low British thermal unit coal gasification pilot plant at the Morgantown Energy Research Center, Morgantown, West Virginia. Results of completed and ongoing chemical V apor deposition research are presented.
OP; Journal Article
Issue of Publication
Thin Solid Films
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division