Accession Number : AD0816147

Title :   STUDIES OF OXIDATION OF NIOBIUM ALLOYS AT VERY HIGH TEMPERATURES.

Descriptive Note : Final rept., 1 Oct 65-30 Sep 66,

Corporate Author : CENTRAL INST FOR INDUSTRIAL RESEARCH OSLO (NORWAY)

Personal Author(s) : Kofstad, Per ; Kvernes, Ingard

Report Date : APR 1967

Pagination or Media Count : 64

Abstract : Oxidation of binary Hf-Nb alloys with 10-50wt%Nb and a few corresponding alloys with ternary additions of Cr, Ti, V, and W has been studied in the temperature range 800-1300 C. Most of the studies were carried out at 10 torr O2, but the oxidation of one binary alloy (Hf-34wt%Nb) was also studied as a function of oxygen pressure. The major reaction products are HfO2, Nb2O5, and Nb2O5 6HfO2. At and above 10 torr O2 the oxidation of the binary alloys increase with temperature up to 900-1000 C, where the oxidation goes through a maximum and then decreases up to about 1100 C. Above 1100 C the oxidation again increases with temperature. This maximum is interpreted as a result of an interplay between relative rates of formation of HfO2 and Nb2O5 and their subsequent reaction to form Nb2O5 6HfO2. The ternary alloy additions of Cr, Ti, and W did not significantly change the oxidation rates. Catastrophic oxidation was observed for Hf-25w/oNb-52/oV and Hf-20w/oNb-10w/oV alloys above 1000 and 900 C, respectively. The binary Hf-Nb alloys showed poor oxidation resistance, and at 900-1000 C the oxidation is as fast as for unalloyed niobium. (Author)

Descriptors :   *OXIDATION), (*NIOBIUM ALLOYS, (*HIGH TEMPERATURE, OXIDATION), HAFNIUM ALLOYS, CHROMIUM ALLOYS, TITANIUM ALLOYS, VANADIUM ALLOYS, TUNGSTEN ALLOYS, PRESSURE, THERMOGRAVIMETRIC ANALYSIS, TANTALUM ALLOYS, ARC MELTING, X RAY DIFFRACTION, ELECTRON MICROSCOPY, METALLOGRAPHY, IONS, HARDNESS, CORROSION RESISTANCE.

Subject Categories : Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE