RESEARCH ON CRITERIA FOR SELECTION OF ALLOYS AND SURFACE TREATMENTS FOR INHIBITION OF TUNGSTEN OXIDATION. PART I. STUDIES ON THE CHEMICAL AND PHYSICAL PROPERTIES OF TERNARY PHASES CONTAINING TUNGSTEN AND OXYGEN.
Rept. for 1 Jul 63-30 Jun 64,
TEM-PRES RESEARCH INC STATE COLLEGE PA
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A study was made of reactions and equilibria as well as the properties of ternary phases which result, thermo physical and thermochemical properties of tungsten and tungsten-base alloy oxidation. Sealed capsules were used to equilibrate pelletized samples from which data were obtained on the condensed phase relations in the systems W-O, Ti-W-O, Ca-W-O, Sm-W-O, and Co-W-O. The system W-O up to 1700C 3090F and isothermal sections for the ternary systems at 1400C 2550F and 1700C 3090F are presented. Because sealed sample containers were used during equilibration, data on the partial pressures of oxygen necessary for equilibrium and on the total pressures of the gas phase could not be obtained. Nevertheless, the positions of the oxygen isobars in the system W-O have been calculated from published thermodynamic data and extrapolations thereof, and generalities which are applicable to the ternary equilibria and which are governed by thermodynamics and the phase rule are stated. Similarly, the processes whereby changes in condensed phase assemblages occur as a function of oxidation of tungsten-metal alloys and mistures are illustrated with examples. Thhe ternary tungstates which are thermodynamically stable in the systems studied have been characterized as to x-ray diffraction pattern and melting temperature. Where possible, crystallographic information is also given. Author