HIGH-TEMPERATURE CHEMICAL STABILITY OF REFRACTORY-BASE ALLOYS IN HIGH VACUUM

Evaporation losses of refr&tory-bise a l l o y s having the comercial designations T-111, FS-80, FS-85, B-66, C-U9Y, and D-43 were determined for various periods of time'at temperatures between 1200 and 1500°C.The experimehtal pressures ranged from 7 X 10'~ t o 6 X 10'1° torr.I n general, there +re no serious evaporation problems associated with these alloys, especially at temperatures of 1200 t o 1300°C.The alloys t h a t i .exhibited the greatest evaporation losses contained the higher vapor-!, .pressure elements such as vanadium, zirconium, and hafnium.For kxmple, !I ' B-66, t h e most volatile allbys studied, l o s t 1.70 mg/cm2 at 1500°C and 7 X 10" tom i n 316 hr, while at 1200°C and 6 x It *Reaesrch sponsored by the U.B. A h d c Energy C d s e i m w&r cantrant a .I ) -, w i t h w e h i o n %-bide Corporation.e , I 5.