Bonded lead monoxide films as solid lubricants for temperatures up to 1250 degrees F Page: 4 of 27
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The rider specimens for all tests run at temperatures up to 10000 F
were K- tool steel hardened to Rockwell C-60. Both M-1 and cast Inconel
riders were used at higher temperatures. The disk specimens (2.5-in.
diam, 0.5-in. thickness) to which the coatings were fused were SAE 1020
steel and 440-C stainless steel. The rider specimens were cylindrical
(3/8-in. diam and 3/4-in, length) and had a hemispherical tip (3/16-in.
rad) ground on one end. Before the coatings were applied, the surfaces
of the disks were ground flat and had a roughness of 4 to 8 rms.
A diagrammatic sketch of the apparatus used to determine friction,
wear, and endurance properties of the solid-lubricant coatings is shown
in figure 1. The basic elements of this apparatus were the rotating
disk specimen and the cylindrical rider specimen with a hemispherical
contact tip. The rotating specimen was driven through a belt system by
an electric motor coupled with a variable-speed power transmission device.
This arrangement allows good speed control with a range of sliding veloc-
o cities up to approximately 500 feet per minute. Loading was obtained by
the use of dead weights to apply force through the pulley system shown
in figure 1. The net loads on the sliding contact were from 200 to
2000 grams (with steel specimens, these loads given initial Hertz surface
stresses from 87,000 to 188,000 psi). The disk and rider specimens were
operated in an Inconel pot. The pot has strip heaters mounted on its
periphery and ring heaters under its base, and thus served as a furnace.
Temperatures up to 12500 F can be obtained in the furnace pot.
The rider-holder assembly was located by rolling contact bearings
with the shaft free to move axially and to rotate within the bearing
housing. The apparatus was insensitive to the very small friction losses
in the bearings. Contact of the rider specimen with the disk provided
axial location Of the rider-holder assembly when the load was applied.
Friction force was measured by four strain gages mounted on a copper-
beryllium dynamometer ring. The strain gages were part of a Wheatstone
bridge circuit. The friction coefficients reported are the ratios of
friction force to applied normal load. Friction coefficients were usually
reproducible within 0.02.
The following procedure was used in coating the disks and preparing
them fot testing:
NAMA R- 357315
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Sliney, Harold E. & Johnson, Robert L. Bonded lead monoxide films as solid lubricants for temperatures up to 1250 degrees F, report, May 7, 1957; (digital.library.unt.edu/ark:/67531/metadc63196/m1/4/: accessed February 20, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.