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REFRACTORY COATINGS FOR TUNGSTEN
NEW YORK UNIV N Y SCHOOL OF ENGINEERING AND SCIENCE
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A study of the feasibility of protecting W wires against oxidation at 3300 F was undertaken. An WSi2 coat was the most promising coating for this temperature. Several siliconizing methods were given a cursory treatment, and the simplest, cementation, was selected for closer investigation. This operation was performed under flowing H atmosphere and such variables as temperature, time, and composition of the cementation pack. A single brittle WSi2 layer is formed by this method. Pack-siliconized wires can withstand oxidation at 3300 F in still air for 10 or more hours. A drawback of the disilicide coat is its low temperature oxidation which occurs in parts exposed at 1200 and 2280 F for prolonged periods. Attempts to deposit ZrO2 on top of siliconized wires by means of plasma arc spray method remained largely unsuccessful. Author
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