KINETICS OF OXIDATION OF NIOBIUM AND ITS ALLOYS

Journal Article · Sun Jan 01 04:00:00 EST 1961 · Issledovaniya po Zharoproch. Splavam, Akad. Nauk S.S.S.R., Inst. Met. im. A.A. Baikova

OSTI ID:4775677

Arzhanyy, P M; Volkova, R M; Prokoshkin, D A

The oxidation of niobium after alloying its surface with various elements was studied. Niobium of the following chemical composition was used as the material for study: 98.9% Nb, 0.4% Ta, 0.15% Pb, 0.13% Fe, 0.08% N, 0.09% O, 0.01% Si, 0.14% C and 5 x 10/sup -5/% B. The hardness of the material was 200 kg/ mm2. The material was made into specimens, which were subjected to cementation with Si and Ti. The diffusion layer was analyzed metallographically and by x-ray spectral methods, as well as by microhardness measurements. The distribution of the diffusion components through the depth of the protective layer was also measured. The specimens were tested for oxidation by continuous weighing with an accuracy of plus or minus 0.0005 g. The oxidized layer was studied metallographically and by means of x-ray and electronographic methods. During saturation of Nb with Ti and Si, diffusion layers of complex structure and composition form. At 900-1100 deg C, a single layer having a microhardness of approximately 1200 kg/mm/sup 2/ forms, and at 1200 and 1300 deg C two layers form, the thickness of the second layer being 5-6 mu . The microstructure and microhardness measurements show that the same phase forms on the surface of saturated specimens at all temperatures and times of soaking. By means of x-ray spectral structural analyses, it was found that the phase consists of niobium disilicide in which Ti is dissolved; this has a hexagonal lattice with parameters a = 4.779 KX and c = 6.493 KX. The Nb content of the second layer is approximately 82%. The phases s. Ti and Nb form a continuous series of solid solutions, and it was assumed that the second phase consists of a solid solution of Ti/sub 5/Si/sub 3/ and Nb/sub 5/Si/sub 3/. The thickness of the diffusion layers forming on the surface of Nb depends on temperature and time for formation. Niobium surfaces protected by Si and Ti oxidize nearly one and a half times more slowly at 1200 deg C than ones protected only by Si. The scale formed is thin, strong, and well adherent. (OTS)

• Research Organization: Originating Research Org. not identified
• NSA Number: NSA-16-032085
• OSTI ID: 4775677
• Journal Information: Issledovaniya po Zharoproch. Splavam, Akad. Nauk S.S.S.R., Inst. Met. im. A.A. Baikova, Journal Name: Issledovaniya po Zharoproch. Splavam, Akad. Nauk S.S.S.R., Inst. Met. im. A.A. Baikova Vol. Vol: 7
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

BORIDES
CARBIDES
CEMENTS
CRYSTALS
DIFFUSION
DISTRIBUTION
FILMS
HARDNESS
HIGH TEMPERATURE
IRON ALLOYS
LATTICES
LEAD ALLOYS
MATERIALS TESTING
METALLOGRAPHY
METALS, CERAMICS, AND OTHER MATERIALS
NIOBIUM
NIOBIUM ALLOYS
NITRIDES
OXIDATION
OXIDES
REACTION KINETICS
SILICIDES
SOLID SOLUTIONS
SPECTRA
SURFACES
TANTALUM ALLOYS
THICKNESS
TITANIUM ALLOYS
X RADIATION