Plasma spraying was used to produce continuously graded and layered structures of molybdenum disilicide and alumina. These microstructures were achieved by manipulating the powder hoppers and plasma torch translation via in-house created computer software. The resultant microstructures sprayed uniformly and were crack free. The mechanical and thermal performance of these sprayed materials will be evaluated through C-ring tests and thermal cycling experiments respectively. The purpose of this study is two fold; firstly to demonstrate the ability of produce such composite ceramic microstructures using a conventional plasma spraying process, and secondly to quantify the improvements in thermo-mechanical performance provided by these composite microstructures over conventional monolithic microstructures.

This paper investigates the stability of molybdenum base silicides, which are located in combustion chambers and in an endothermic environment, for use in radiant tubes for heat treatment. The subject matter was plasma-sprayed molybdenum disilicide, pentamolybdenum trisilicide, hot-pressed molybdenum disilicide, and molybdenum disilicide composites containing SiC and silicon nitride reinforcements. Results of the investigation show that the oxidation resistance of plasma sprayed molybdenum disilicide can be detrimentally effected due to the silicon loss that occurs during the high temperature plasma spray process. Paper includes a German-language abstract.