• Version
• 124 Downloads
• 2.63 MB File Size
• 1 File Count
• December 4, 2016 Create Date
• December 4, 2016 Last Updated

National Advisory Committee for Aeronautics, Technical Notes - Friction of Solid Films on Steel at High Sliding Velocities

An experimental investigation was conducted to identify the
roles of solid-surface films in the various mechanisms of sliding
and lubrication involved. in the mating and ounpatibility of
boundary-lubricated slider surfaces, in the action of extreme-
pressure lubricants, and in the operation of slider surfaces not
supplied with fluid lubricants.

The experiments were performed. with an apparatus incorporating
means for measuring sliding-friction that consisted basically of an
elastically restrained spherical rider sliding in a spiral path on
a rotating disk. The disk specimens were treated to produce solid-
surface films of various inorganic compomds. The experiments were
conducted over a range of sliding velocities between 50 and
8000 feet per minute with loads fran 169 to 1543 grams (108,000 to
225,000 lb/sq 111., initial Hertz surface stress). Bupplanental
studies of friction specimens were made using standard physical,
chemical, and metallurgical equipment and. techniques including
electron diffraction.

Molybdenum disulfide M082 was very effective in reducing
friction at high sliding velocities. This film material was very
tenacious, was chemically and themally stable, and consequently
should have many practical applications.

It was determined that the formation of ferroso-ferric
oxide on - F9304 on run-in sliding surfaces was beneficial with

respect to friction and wear. Preoperational treatment at slider
surfaces to form a. - F9304 may be accomplished by a number of
inexpensive and comon proprietary camercial processes. Ferric
oxide or. - Fezos, however, was not beneficial with respect to
friction and wear over the entire range of sliding velocities.

Ferrous chloride FeClz was more effective in reducing
kinetic friction than ferrous sulfide 398. This result would
seem to indicate that chlorine compounds were more effective as
extreme-pressure lubricant additives than were sulfur ocmpounds.
Abrupt changes in friction, with increased sliding velocities,
indicated critical material transformations of ferrous-chloride
films. This condition favored the theory of the action of extreme-
pressure lubricants, which state that the film material, foamed by
reaction of the lubricant additive with a surface, melts under
extranely high temperatures or pressures and in that case the
friction force will involve only shearing of a liquid film.