1. Recently we have been able to make life predictions for the MoS2+Sb2O3+Au coating using the reciprocating tribometer pictured. By taking optical profilometry scans of the sample surface after each passing cycle we are able to examine the wear process during the life of the coating. Because the tribometer resides in an environment chamber, tests can be run in both ambient conditions and dry N2.

2. Here are individual profilometer scans taken at the indicated cycles during a test. We can now examine transient and steady state wear evolution during testing and account for individual anomalies in friction coefficient by investigating the appropriate surface scans.

3. A life test simulation of the coating was also performed on this tribometer where 20k cycles were performed in ambient air followed by 5k cycles in dry N2. volume loss measurements were taken throughout the test to determine a wear rate for the coating.

4. These are just the graphs if you want to cut an paste them into another presentation.

5. Simple Models for Wear Life Prediction

6. Wear rates for the MoS2+Sb2O3+Au coatings were extracted from the studies and design charts for coated shafts and bushings were constructed. Using coating thickness, contact pressure, and shaft radius designers can use the above chart to estimate how many cycles the coating will remain on the shaft.

7. Using coating thickness, contact pressure, and shaft radius designers can use the above chart to estimate how many cycles the coating will remain on the bushing. Assuming both the shaft and bushing are coated to the same thickness, the bushing is the more critical design part.

8. Summary Data for Life Testing of MoS2 Coatings
Here we summarize the friction and wear behavior of the MoS2 based coatings in both ambient air and dry nitrogen. These values should be considered when using the design charts.

9. Vacuum Linear Reciprocator
Test Samples

10. W2A Hub Carrier Clevis Journal Test Results
Test Date
Environment
Load
[N]
Contact Pressure
[psi]
Velocity
[mm/s]
# Cycles for 1 Life
# Reciprocation for 1 Life
Cycles to Failure
Measured Friction Coefficient
Temp
[C]
Pressure
[Torr]
2/25/08
Ambient
152.5
44000 10
50 Deploy/ 50 Stows 50
Survived
.054 30
7.60E+02
13.9
4000 20
10,000 Vibrational Cycles
10,000
.176
2/26/08
High Vacuum
10 Deploy Deploy
.047
-75
1.92E-06
.041 70
7.51E-06
Note: These experiments were just completed 2/26/2008 this is a MoS2/Au/Sb2O3 coating. The higher friction coefficient with the reduced load is not surprising. Recall, this follows a very tough load condition for the coating at ambient pressure.