ISSN:
1573-4889
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The effects of presulfidation in H2-H2S atmospheres of sulfur activity sufficient to form cobalt and chromium sulfides on the oxidation rates of Co-Cr binary alloys containing 0–25 wt.% Cr and Co-25 wt.% Cr alloys containing 0–2 wt.% C have been investigated. Presulfidation increases the oxidation rate, but the effect is not very dramatic. Carbon additions to the Co-25 wt.% Cr alloy progressively increase the oxidation rate, but not to as great an extent as a simple model based on the reduction of the chromium activity in the alloy. Sulfur released from the preformed sulfides by oxidation diffuses into the alloy precipitating fresh sulfides, there appears to be no outward diffusion of sulfur through the oxide scale. These internal sulfides have a liquid-like morphology in cobalt-base alloys when the oxidation is carried out at 1000°C, as compared to 800°C in corresponding nickel-base alloys. When the sulfide layer produced during the presulfidation is thin, so that oxidation destroys the continuous sulfide layer, the subsequent scale morphologies after oxidation exhibit many features similar to samples subjected to hot corrosion in environments containing sodium sulfate.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00604040
