The Reduction of the Impact Transition Temperature of Chromium Composites.

The effect of varying the vacuum sintering temperature of Chrome-XT alloys Chrome-90S between 2750F and 2850F was investigated. No definite trend was evident, and three hours at 2800F was used in the preparation of subsequent chromium alloys. Minor compositional variations were made in the preparation of subsequent chromium alloys. Minor compositional variations were made in the Chrome-XT class of alloys to improve the impact transition temperature. A reduction of the impact DBTT from 1100F to 550F resulted from lowering the amount of strengthening additives including vanadium, silicon, and tantalum and elimination of carbon and vanadium carbide additions. For comparison Chrome-90 has an impact DBTT of 550F. This new group of Chrome-XT alloys had some of the tensile properties of the stronger alloys higher yield strength and reduced ductility. A connection between tensile and impact transition temperature and the interstitials present was hinted. A feasibility study to determine whether Chrome-90 would be compatible with some type of filament or wire reinforcement was conducted. Silicon carbide, Borsic, and alpha - alumina were not acceptable because of the techniques used for fabrication. Tungsten and two tungsten alloy wires survived the fabrication and were bonded to the Chrome-90 matrix. Oxidation-nitridation testing was conducted on the alloys from both phases of the study. Author