Chrome Oxide Ring Plasma Sprayed And Liner Coatings

Figure 9 shows friction coefficient results from the Hohman-A9 tester for the plasma sprayed chromium oxide ring and plasma sprayed chromium oxide liner coating without lubrication at 427 C. Note that the friction coefficient increased somewhat during the course of the test. This is combination 2 of Table 1. After two hours of testing the friction coefficient reached 0.55. Figure 10 shows the surface of the sample prior to testing at a sample interval of 39 v-in. Figure 11 shows the results after testing at sampling intervals of both 39 and 281 ixin. respectively. In general the surface was somewhat smoother, but relatively little material was removed. In comparison with the titanium carbide, chrome carbide result of Figure 5, this combination shows relatively little surface wear throughout the entire stroke. We may conclude that the Hohman-A9 tester ranks this material to be relatively durable under these severe operating conditions. As expected. the use of synthetic oil A reduced the friction coefficient significantly. Figure 12. This is combination 4 of Table 1. After two hours the friction coefficient averaged about 0.15. Again wear rates were too low to be measureable.

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