Accession Number : AD0477115


Title :   INVESTIGATION OF MODIFIED SILICIDE COATINGS FOR REFRACTORY METAL ALLOYS WITH IMPROVED LOW-PRESSURE OXIDATION BEHAVIOR.


Descriptive Note : Final rept. 1 Jun 64-31 May 65,


Corporate Author : LOCKHEED MISSILES AND SPACE CO INC PALO ALTO CA MATERIALS SCIENCES LAB


Personal Author(s) : Lavendel, Henry W ; Elliot, A G


Report Date : Aug 1965


Pagination or Media Count : 124


Abstract : A study of modifications of silicide coatings on columbium and tantalum was conducted to explore the feasibility of upgrading the protective performance of these coatings in low-pressure oxidizing atmospheres. Stabilization of the coatings was sought against loss of silicon by both diffusion into the substrate and volatilization into the environment. For this purpose, disilicide phases in the coatings were replaced by the intermediate compounds Me5Si3 which are characterized by lower silicon activity. Both the disilicides and the intermediate silicides were alloyed by substituting aluminum for part of the silicon to form Me(Si,Al)2 and Me5(Si,Al)3, respectively, and protective glass layers were formed on the as-produced coatings. Also, commercial titanium-modified disilicide coatings were investigated. The coated samples were tested for oxidation behavior by resistance heating in static air at pressures between 1 and 760 Torr. Behavior of modified coatings was compared with that of straight disilicides, at temperatures between 2200 and 3200 F. (Author)


Descriptors :   COATINGS , SILICIDES , OXIDATION , LOW PRESSURE , NIOBIUM ALLOYS , TANTALUM ALLOYS , ALUMINUM ALLOYS , TANTALUM , SUBSTRATES , SILICON COMPOUNDS , DIOXIDES , MONOXIDES , ALUMINUM COMPOUNDS , OXIDES , TANTALUM COMPOUNDS , MICROSTRUCTURE , OPTIMIZATION , LIFE EXPECTANCY(SERVICE LIFE) , CRYSTAL STRUCTURE , CRYSTAL LATTICES , HEAT OF ACTIVATION , EMBRITTLEMENT , MOLYBDENUM COMPOUNDS


Subject Categories : Polymer Chemistry
      Properties of Metals and Alloys


Distribution Statement : APPROVED FOR PUBLIC RELEASE