ISSN:
1573-4889
Keywords:
Alloy oxidation
;
cobalt-chromium-tungsten
;
scale formation
;
kinetics
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Oxidation rates in air at 1000–1250°C are reported for a series of Co-Cr-W alloys with 34–40 wt. % Cr and up to 10 wt. % W. Alloys with larger W contents exhibited slower oxidation rates and their parabolic rate constants agreed well with those for binary and ternary, Cr2O3 protected, Ni-base and Co-base alloys in the Co-Cr and Ni-Cr-W systems. The resulting scales were characterized by optical and scanning electron metallography, and electron microprobe analysis. The favorable effect of W additions to a Cr2O3-forming Co-Cr base alloy was the opposite of that reported for Ni-Cr-W alloys. The resupply of Cr to a Cr-depleted matrix beneath a protective CrO3 scale is achieved by the dissolution (denuding) of Cr-rich second phases in the Co-Cr-W alloys. Thus, the internal oxidation of Cr beneath the Cr2O3 scale is avoided for high W alloys. No catastrophic failure by liquid phase formation was observed for high-W alloys oxidized 20 hr at 1250°C.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00658126
