THE OXIDATION PROPERTIES OF A ZIRCONIUM-2.7 W/O NIOBIUM ALLOY IN THE TEMPERATURE RANGE 300-500C
Abstract
The reaction kinetics and structures of the alloy/oxide composite system were determined for martensitic and several Widmanstatten-structured alloys oxidized at 300, 400, and 500C in oxygen at 1 atm pressure. At 300 and 400C, there was little difference between the oxidation rates of the differently structured alloys in the early stages of the reaction. Prolonged exposures illustrated the occurrence of two limiting oxidation curves: martensitic specimens oxidized most rapidly, the oxidation rate decreasing until a transition range was attained in which the rate subsequently increased to a maximum value associated with linear kinetics; on the other hand, Widmanstatten- structured specimens containing equilibrium amounts of proeutectoid alpha- zirconium from the quench temperature oxidized most slowly, the initial decreasing oxidation rates finally approximating to linear kinetics at long exposures. Specimens containing intermediate amounts of proeutectoid alpha- zirconium oxidized at rates between these two limiting cases. At 500C, the initial oxidation rates for all alloys approximated to parabolic kinetics, the reaction rate constants being directly dependent on the volume fractions of martensite. The major product of the reaction at all temperatures irrespective of alloy structure was an oxide whose structure could be indexed as monoclinic zirconia.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 02, 1967
- Accession Number
- AD0664969
Entities
People
- M. G. Cowgill
- W. W. Smeltzer
Organizations
- McMaster University