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Method of Applying Molybdenum Disilicide Coatings

IP.com Disclosure Number: IPCOM000085661D
Original Publication Date: 1976-May-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Swiss, WR: AUTHOR [+2]

Abstract

The problem of applying an even and continuous coating of molybdenum disilicide on molybdenum parts to improve oxidation resistance has restricted it's application. A precisely controlled thickness of the disilicide coating can be easily applied even to interior sections of molybdenum parts by vapor deposition.

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Method of Applying Molybdenum Disilicide Coatings

The problem of applying an even and continuous coating of molybdenum disilicide on molybdenum parts to improve oxidation resistance has restricted it's application. A precisely controlled thickness of the disilicide coating can be easily applied even to interior sections of molybdenum parts by vapor deposition.

The articles to be coated are placed in a high-temperature kiln, suitable for hydrogen use. The furnace is then heated to a minimum of 1300 degrees C in hydrogen at a controlled partial pressure of oxygen in the presence of phosphosilicate glass. The silicon becomes available from the glass as the silica, SiO(2), is reduced to SiO with the phosphorus acting as a catalyst to trigger the reaction.

The articles are coated by the silicon vapor and the coating becomes strongly bound to the newly coated part. The amount of the silicide coating can be easily controlled by limiting the amount of phosphosilicate glass used, or by limiting the time above 1300 degrees C. The rate of deposition can be controlled with temperature and oxygen partial pressure.

The reduction of silica starts at approximately 1250 degrees C and rapidly increases up to approximately 1500 degrees C at low oxygen partial pressures (< 10 degrees C dew point). The rate of deposition is controlled with oxygen partial pressure by use of a gas saturation.

The reduction rate drops to essentially zero at dew points greater than 30 degrees C and rapid...