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Figure 8. Four-Ball Wear Values at 370 C with Vapor Lubrication as a Function of TCP Vapor Concentration presented in this paper, gives a deposit rate of about two molecular layers of deposit per second at 370°C. The rotating ball in the four-ball wear tester provides the rubbing surface available for vapor deposition during the test. At 600 rpm and contact with the three stationary balls, there are 300 contacts per second for the rotating ball. Four-ball wear data are presented on Figure 8 for 30 minute tests at a 10 kilogram load. The Hertz line is shown to indicate zero wear. These data show a decrease in wear with increasing TCP vapor concentration to a minimum wear value and then an increase in wear as the concentration of TCP continues to increase. The wear reduction with increasing concentration, appears to indicate that the increase in deposit rate is needed to provide adequate deposition to provide an easily sheared chemical film over th entire work area. The increase in wear beyond the concentration that yields minimum wear values appears to be due to three body wear. At these higher deposition rates, there appears to be a net build up of TCP deposit which tends to mix with the wear debris and keep both the deposit and wear debris in the wear track, resulting in some abrasive wear. At the high end of the TCP concentration level on Figure 8 the wear scars were actually observed to contain a build up at the trailing edge of the scar of a layer of material containing TCP coating and metal wear debris. The actual wear values from Figure 8 can be compared with those of typical industrial and motor oils conducted in a four-ball wear tester run under the liquid lubricant at 75 C. The comparison is shown in Figure 9. These data indicate that at an optimum concentration TCP vapor provides the same level of the low wear in the four-ball wear tester at 370°C as is obtained from a state of the art 10W-30 (sf-cd) automotive lubricant at 75°C as a liquid lubricant. An industrial EP lubricant and a typical rust and oxidation inhibited industrial lubricant have also been run, using liquid lubricant at 75 C. The vapor delivered TCP values in the four-ball wear tester at 370°C shows clear evidence of good boundary lubrication.

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