ISSN:
1573-4889
Keywords:
V-A1 alloy
;
Cr and Ti additions
;
oxidation
;
kinetics
;
V2O5
;
Al2O3
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The oxidation behavior in air of pure vanadium, V-30Al, V-30Al-10Cr, and V-30Al-10Ti (weight percent) was investigated over the temperature range of 700–1000° C. The oxidation of pure vanadium was characterized by linear kinetics due to the formation of liquid V2O5 which dripped from the sample. The oxidation behavior of the alloys was characterized by linear and parabolic kinetics which combined to give an overall time dependence of 0.6–0.8. An empirical relationship of the form: ΔW/A=Bt + Ct1/2 + D was found to fit the data well, with the linear contribution suspected to be from V2O5 formation for V-30Al and V-30Al-10Cr, and a semi-liquid mixture of V2O5 and Al2O3 for V-30Al-10Ti. The parabolic term is presumed related to the formation of a solid mixture of V2O5 and Al2O3 for V-30Al and V-30Al-10Cr, and TiO2 for V-30Al-10Ti The addition of aluminum was found to reduce the oxidation rate of vanadium, but not to the extent predicted by the theory of competing oxide phases proposed by Wang, Gleeson, and Douglass. This was attributed to the formation of a liquid-oxide phase in the initial stages of exposure from which the alloys could not recover. Ternary additions of chromium and titanium were found to decrease the oxidation rate further, with chromium being the most effective. The oxide scales of the alloys were found to be highly porous at 900° C and 1000° C, due to the high vapor pressure of V2O5 above 800° C.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01151591
