Rare earth trifluorides have potential use as lubricating fillers for mechanical carbons and as coatings on metallic substrates. Friction experiments show that they are effective in reducing metallic wear

Sliney, H. E.

English

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June 1970	 Brief 70-10175 
NASA TECH BRIEF 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the Clearinghouse for Federal Scientific and Technical 
Information, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
High Temperature Rare Earth Solid Lubricants 
.
Results from a study of the rare earth fluorides 
(CeF3 and LaF3), conducted at temperatures ranging 
from 1800°F or higher, have indicated that they have 
good potential for use as solid lubricants. Other 
characteristics of the rare earth fluorides, such as 
moderately high friction coefficient, combined with 
good antiwear properties, suggest possible use in 
power transmission devices such as clutch plates and 
brakes, and as fillers in mechanical carbons. Tests also 
showed that these fluorides exhibited fairly low hard-
ness (4.5 on the Moh scale); hexagonal crystal struc-
ture; thermal expansion coefficients which match 
those of substrate metals such as nickel base super 
alloys and stainless steels; and water insolubility. In 
addition, they have good chemical stability and melt-
ing points above 200°F (1200°C). 
Friction experiments with powdered rare earth 
fluorides were conducted in argon and air atmospheres 
from room temperature to 1800°F. The specimen 
configuration consisted of Inconel 600 riders sliding on 
a stationary Inconel 750 disc, lubricated with a thin 
layer of powdered CeF3 or LaF3. The data showed 
that, in general, the rare earth trifluorides were effec-
tive in reducing metallic wear. In both atmospheres 
and over a large temperature span (500 0 to 18000F), 
the friction coefficients were within the range of 0.1 
to 0.4, which is typical of the friction coefficients ob-
tained with many grades of mechanical carbons ,, in 
commercial use as sliding contact bearing and seal 
materials. This suggests that rare earth fluorides such 
as LaF3 may be useful as lubricating fillers for 
mechanical carbons, especially for high temperature 
applications. 
Fused-fluoride coatings were then prepared and 
evaluated. The compositions were: LaF3 with 25
weight percent of a CaF2-BaF2 eutectic and CeF3 
with 12 weight percent LiF eutectic. These composi-
tions were readily fused on metal substrates at 1600°F 
in a hydrogen atmosphere and, upon cooling, formed 
adherent coatings. Friction experiments with both 
compositions showed that the CeF3 composition had 
lower friction coefficients than the LaF3 coating. The 
CeF3-LiF coating was relatively insensitive to tem-
perature in the range from room temperature to 
1200 0 F. The frictioi coefficient was 0.4 at room 
temperature and gradually decreased to 0.3 at 1200'F. 
Notes: 
I. The following documentation may be obtained 
from:
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.65) 
Reference: 
NASA-TN-D-5301 (N69-29568), Rare 
Earth Fluorides and Oxides—An Ex-
ploratory Study of Their Use As Solid 
Lubricants at Temperatures to 1800°F 
(1000°C) 
Technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B70-10175
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately ownedrights.
https://ntrs.nasa.gov/search.jsp?R=19700000169 2020-03-17T00:29:36+00:00Z
Patent status: 
No patent action is contemplated by NASA. 
Source: Harold E. Sliney 
Lewis Research Center 
(LEW- 10983) 
Brief 70-10175
Category 04


High temperature rare earth solid lubricants

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