The Air Force Wright Laboratory Materials Directorate awarded the program, 'Thermal Control Coatings for High Thermal Conductivity (K) Substrates' to Lockheed Martin Vought Systems to investigate plasma sprayed thermal control coatings. The program objective is to optimize, space qualify, demonstrate and transition plasma sprayed thermal control coatings for high thermal conductive substrates. The current program accomplishments include developing constituent powder refinement processes for low cost high purity alumina, applying the high purity alumina constituents to multiple substrates, establishing repeatable applications, optimizing the plasma spray parameters, and testing the high purity alumina based thermal control coatings for combined radiation environment at the Wright Laboratory Space Combined Effects Primary Test and Research (SCEPTRE) facility. Additional activities will include evaluating atomic oxygen and vacuum ultraviolet effects at the Atomic Oxygen and Vacuum Ultraviolet Combined Effects NASA Lewis Research facilities. Results from the Taguchi designed experiments indicate that the program goal of beginning of life low solar absorptance (0.15) was successfully obtained and reproduced from plasma sprayed ultra high purity alumina and alumina/zirconia/yttria. Solar absorptance values of approximately 0.12 were predicted and produced in the follow on Taguchi experiment for a coating thickness of 0.015 inch for the ultra high purity alumina. This compares to previously reported solar absorptance values for plasma sprayed alumina of 0.17-0.30. The SCEPTRE test results for the ultra high purity alumina have shown the end of life solar absorptance of 0.22 for 1.2 suns (858 equivalent sun hours or ESH), 0.21 for 2.2 suns (1507 ESH), and 0.23 for 2.8 suns (2030 ESH) exposures. The SCEPTRE and NASA Lewis tests are ongoing for the alumina/zirconia/yttria candidates. This paper represents work in progress and the approach used for evaluating ultra high purity blended plasma spray powders.
Plasma sprayed ultra high purity alumina based thermal control coatings
1998
8 Seiten, 6 Quellen
Conference paper
English
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