Evaluation of vanadium and vanadium-base alloys in hot-trapped sodium

Abstract

Corrosion tests were conducted with vanadium-base alloys in zirconium-purified sodium from 450° to 750°C for 500 to 4000 hr. The materials tested were vanadium, binary vanadium alloys containing from 10 to 40 wt pct Ti, and two ternary alloys: V-5Ti-15Cr and V-15Ti-7.5Cr. The sodium was analyzed to contain from 1.7 to 8.7 ppm O by the vacuum-distillation technique. The behavior of these materials was determined from weight change data, and from chemical, metallographic, and electron-microprobe analyses of the test specimens. At temperatures up to 650°C, the maximum weight-change varied from a weight loss of 0.45 for vanadium to a weight gain of 0.46 mg per sq dm-day for the V-40Ti alloy. Chemical analyses of the corrosion test specimens indicated that vanadium-base materials were sensitive to the activity of oxygen, carbon, and/or nitrogen in sodium. Alloys containing >10 wt pct Ti increased in oxygen, carbon, and in some tests, nitrogen content, indicating that alloys of this titanium content are not compatible with sodium of the present purity. Complex titanium carbide precipitates were observed near the surface. V-5Ti-15Cr alloy was more resistant to liquid sodium than the other vanadium materials investigated.