Effects of atmosphere on the tribological properties of a chromium carbide based coating for use to 760 C

Journal Article · Fri Apr 01 04:00:00 EST 1988 · Lubr. Eng.; (United States)

OSTI ID:5006363

Dellacorte, C; Sliney, H E

The effect of atmosphere on the tribological properties of a plasma-sprayed chromium carbide based self-lubricating coating is reported. The coating contains bonded chromium carbide as the wear resistant base stock to which the lubricants silver and barium fluoride/calcium fluoride eutectic are added. It has been denoted as NASA PS200. Potential applications for the PS200 coating are cylinder wall/piston ring couples Stirling engines and foil bearing journal lubrication. Friction and wear studies were performed in helium, hydrogen, and moist air at temperatures from 25 to 760 C. In general, the atmosphere had a significant effect on both the friction and the wear of the coating and counterface material. Specimens tested in hydrogen, a reducing environment, exhibited the best tribological properties. Friction and wear increased in helium and air but are still within acceptable limits for intended applications. A variety of X-ray analyses was performed on the test specimens in an effort to explain the results. The following conclusions are made: (1) As the test atmosphere becomes less reducing, the coating experiences a higher concentration level of chromic oxide at the sliding interface which increases both the friction and wear. (2) Beneficial silver transfer from the parent coating to the counter-face material is less effective in air than in helium or hydrogen. (3) There may be a direct relationship between chromic oxide level present at the sliding interface and the friction coefficient. 7 references.

• Research Organization: National Aeronautics and Space Administration, Cleveland, OH (USA). Lewis Research Center; NASA, Lewis Research Center, Cleveland, OH (USA)
• OSTI ID: 5006363
• Journal Information: Lubr. Eng.; (United States), Journal Name: Lubr. Eng.; (United States) Vol. 44; ISSN LUENA
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
320301* -- Energy Conservation
Consumption
& Utilization-- Industrial & Agricultural Processes-- Energy Sources
33 ADVANCED PROPULSION SYSTEMS
330201 -- External Combustion Engines-- Stirling Cycle
36 MATERIALS SCIENCE
360204 -- Ceramics
Cermets
& Refractories-- Physical Properties
ALKALINE EARTH METALS
ATMOSPHERES
BARIUM
CALCIUM
CARBIDES
CARBON COMPOUNDS
CHROMIUM
CHROMIUM CARBIDES
CHROMIUM COMPOUNDS
COATINGS
ELEMENTS
ENGINES
FLUIDS
FLUORIDES
FLUORINE COMPOUNDS
FRICTION
GASES
HALIDES
HALOGEN COMPOUNDS
HEAT ENGINES
HELIUM
HUMIDITY
HYDROGEN
LUBRICATING PROPERTIES
LUBRICATION
METALS
NONMETALS
PHYSICAL PROPERTIES
PISTONS
RARE GASES
SILVER
STIRLING ENGINES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
TRIBOLOGY
WEAR