As part of a program to develop solid/powder-lubricated journal bearings, a comparative evaluation has been performed to aid in determining whether MoS2 and WS2 powder are suitable lubricants for high-speed, extreme-environment multi-pad journal bearings. Plots of traction coefficients, friction, frictional power loss, and bearing pad temperature are presented as a means for comparing various powder lubricants. This paper primarily focuses on experiments carried out on a three-pad journal bearing and a disk-on-disk tribometer. Results showed that MoS2 traction curves resemble that of SAE 10 synthetic oil. Unlike liquid lubricants, powder films have a limiting shear strength property. Once the powder reaches this limiting value, the maximum traction coefficient is limited and the powder essentially shears along sliding walls. Experimental traction data shows evidence of this property in various powders. The thermal performance of the bearing was evaluated at speeds up to 30,000 rpm and loads up to 236 N. Although WS2 displayed constant friction coefficient and low temperature with increasing dimensionless load, MoS2 exhibited frictional behavior resembling that of a hydrodynamic lubricating film. In this paper, an attempt has been made to provide a criterion for the selection of solid lubricants for use in those tribosystems that may be operated in a high speed/load regime (i.e., high strain rates) as an alternative yard stick to conventional comparative approaches.

1.
Heshmat, H., 1991a, “Development of Rheological Model for Powder Lubrication,” Final Technical Report MTI 91TR31, U.S. Army AVSCOM, NASA contractor report CR-189043.
2.
Heshmat
H.
,
1991
b, “
The Rheology and Hydrodynamics of Dry Powder Lubrication
,”
STLE Tribology Transactions
, Vol.
34
, No.
3
, pp.
433
439
.
3.
Heshmat
H.
,
1991
c, “
High-Temperature, Solid-Lubricated Bearing Development—Dry-Powder-Lubricated Traction Testing
,”
AIAA J. of Propulsion and Power
, Vol.
7
, No.
5
, pp.
814
820
.
4.
Heshmat
H.
,
1992
, “
The Quasi-Hydrodynamic Mechanism of Powder Lubrication; Part II—Lubricant Film Pressure Profile
,”
Journal of STLE
, Vol.
48
, No.
5
, pp.
373
383
.
5.
Heshmat, H., 1993, “Rolling and Sliding Characteristics of Powder Lubricated Ceramics at High-Temperature and Speed,” Presented at the 47th Annual Meeting of the STLE, Philadelphia, Pa., STLE Lubrication Engineering, Vol. 49, No. 10, pp. 791–797.
6.
Heshmat, H., 1994, “On the Theory of Quasi-Hydrodynamic Lubrication with Dry Powder: Application to Development of High Speed Journal Bearing for Hostile Environment,” Proceedings of the 20th Leeds-Lyon Symposium on Dissipative Processes in Tribology, Lyon, France, Dowson et al., ed., Elsevier Science B. V., Tribology Series 27, pp. 45–64.
7.
Heshmat, H., and Brewe, D. E., 1994, “Performance of Powder-Lubricated Journal Bearings with Dry MoS2 Powder: Experimental Study of Thermal Phenomena,” Accepted for publication by ASME Trans., JOURNAL OF TRIBOLOGY, and presented at the ASME/STLE Tribology Conference, Lahaina, Hawaii.
8.
Heshmat, H., and Brewe, D. E., 1995, “Performance of a Powder Lubricated Journal Bearing with WS2 Powder: Experimental Study,” Presented at the ASME/STLE Tribology Conference, ASME JOURNAL OF TRIBOLOGY, Vol. 117, pp. 1–8.
9.
Heshmat
H.
, and
Dill
J. F.
,
1992
, “
Traction Characteristics of High-Temperature, Powder-Lubricated Ceramics (Si3N4/αSiC)
,”
STLE Transactions
, Vol.
35
, No.
2
, pp.
360
366
.
10.
Heshmat, H., Godet, M., and Berthier, Y., 1995, “On the Role and Mechanism of Dry Triboparticulate Lubrication,” Pittsburgh, Pa., STLE, Lubrication Engineering, Vol. 51, No. 7, pp. 557–564.
11.
Murray
S. F.
, and
Calabrese
S. J.
,
1993
, “
Effect of Solid Lubricants on Low Speed Sliding Behavior of Silicon Nitride at Temperatures to 800°C
,”
STLE Lubrication Engineering
, Vol.
49
, No.
12
, pp.
955
964
.
12.
Stachowiak, G. W., and Batchelor, A. W., 1993, Engineering Tribology, Tribology Series 24, Elsevier Science Publishers B. V., Amsterdam, pp. 416–417.
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