Oxidation protection for a variety of transition metals and copper via surface silicides formed with silane containing atmospheres

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Abstract
The reaction of SiH4/H2 mixtures with iron, cobalt, nickel, copper, chromium, molybdenum, and tungsten, at temperatures between 350 and 800 °C and 1 atm of total pressure, was studied. When the amount of water vapor in the gas mixture is carefully controlled, a metal silicide diffusion coating forms at the appropriate treatment temperature. Cu silicide coatings form at temperatures as low as 350 °C. Metal silicide coatings for Fe, Ni, Co, and Cr form at intermediate temperatures (500–700 °C), and higher temperatures (above 700 °C) are required for W and Mo. Composition and structure of the metal silicide coatings were determined by Auger depth profiling and x-ray diffraction. Kinetics of the surface reaction between SiH4 and the metal substrate as well as the behavior of these coatings in oxidizing environments at high temperatures were studied by a microgravimetric technique. The metal silicide coatings provide oxidation protection for Fe, Ni, and Cr in pure O2 up to 1000 °C, for W and Mo in air up to 900 °C, and for Cu exposed to air up to 700 °C.