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determine if any large detachments of coatings should occur. No large spailing of coatings occurred.

Oil samples were drawn from the crankcase at 50 hour intervals. Although 22 elements were analyzed for each sample, iron and chrome were the elements of primary concern, as these are indicators of wear within the engine. The parts per million (ppm) content for both iron and chrome remained normal throughout the test, thus providing an indication that catastrophic wear was not occurring.

Following disassembly of the engine, the coated components were carefully removed and inspected to determine if any loss of ceramic material had taken place. Initially the condition of the coatings was obscured by a thin layer of carbon. It became necessary to remove the carbon and a chalk- like substance, which turned out to be calcium, before the ceramics coatings could be evaluated. The parts were then cleaned and raneasured using the same procedures as for the before-test set of measurements. Average wear measurements are given in Table VII.

The ceramic coatings were examined, following the 500-hour test, through the use of both optical (light microscope) and scanning electron microscopy (SEM). In addition, microhardness indentation analysis was used to evaluate the tendency for microfracture, both within the coating and at the coating- metal interface.

Both coatings A and B were observed to be composed of two major layers with the layer adjacent to the metal being fairly dense and the outer layer being quite porous. The thickness of the two layers was variable, ranging from 0.22 mm to 0.55 mm . On the average, the composite coat thickness was about 0.35 mm. Coating thicknesses, as measured, are given in Table VIII.

Brake horsepower, brake thermal efficiency, and brake specific fuel consumption were compiled and tabulated for the two performance tests that were undertaken during the 500 Hour test. The results are tabulated in Table IX. The percentage difference in all cases was less than one percent for each parameter evaluated. This indicates that no degradation in engine performance occurred during the test.

Peak cylinder pressure was measured in two cylinders (number 1 and 12) during the test. No appreciable difference was found between the peak cylinder pressure as measured for the uncoated cylinder (No.l) and that as measured for the coated cylinder (No.12). Since BHP, BTE, and BSFC are all functions of peak cylinder pressure, it can be inferred that the

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