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LUBRICATING PROPERTIES OF CERAMIC-BONDED CALCIUM FLUORIDE COATINGS ON NICKEL-BASE ALLOYS FROM 75 DEG TO 1900 DEG FThe endurance life and the friction coefficient of ceramic-bonded calcium fluoride (CaF2) coatings on nickel-base alloys were determined at temperatures from 75° to 1900° F. The specimen configuration consisted of a hemispherical rider (3/16-in. rad.) sliding against the flat surface of a rotating disk. Increasing the ambient temperature (up to 1500° F) or the sliding velocity generally reduced the friction coefficient and improved coating life. Base-metal selection was critical above 1500° F. For instance, cast Inconel sliding against coated Inconel X was lubricated effectively to 1500° F, but at 1600° F severe blistering of the coatings occurred. However, good lubrication and adherence were obtained for René 41 sliding against coated René 41 at temperatures up to 1900° F; no blisters developed, coating wear life was fairly good, and the rider wear rate was significantly lower than for the unlubricated metals . Friction coefficients were 0.12 at 1500° F, 0.15 at 1700° F, and 0.17 at 1800° and 1900° F. Because of its ready availability, Inconel X appears to be the preferred substrate alloy for applications in which the temperature does not exceed 1500° F. René 41 would have to be used in applications involving higher temperatures. Improved coating life was derived by either preoxidizing the substrate metals prior to the coating application or by applying a very thin (<0.0002 in.) burnished and sintered overlay to the surface of the coating. Preoxidation did not affect the friction coefficient. The overlay generally resulted i n a higher friction coefficient than that obtained without the overlay. The combination of both modifications resulted in longer coating life and in friction coefficients intermediate between those obtained with either modification alone.
Document ID
19620000009
Acquisition Source
Glenn Research Center
Document Type
Other - Technical Note (TN)
Authors
Harold E Sliney
(Lewis Research Center Cleveland, OH, United States)
Date Acquired
August 1, 2013
Publication Date
February 1, 1962
Subject Category
Metals And Metallic Materials
Report/Patent Number
WGL-PAPER-11
NASA-TN-D-1190
E-1401
Report Number: WGL-PAPER-11
Accession Number
62N10009
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
Keywords
Nickel alloy
Calcium fluoride
Coating
Lubrication
Ceramic bonding
High temperature
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