Springer Online Journal Archives 1860-2000
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Abstract The influence of a uniaxial deformation on the initial oxidation rate of a Ni-20Cr polycrystalline alloy was studied between 550 and 830°C at 10−4 Pa of oxygen. At 550, 650, and 750°C, it was shown that the defects induced by a mechanical predeformation accelerate chromium-oxide formation on the alloy surface. This homogeneous oxide film is characteristic of the low-pressure-oxidation conditions. The film appeared on the sample after various incubation periods for the experimental conditions used. Microanalyses (scanning Auger microanalyses, composition profiles) reveal that growth of this oxide is heterogeneous and that it needs preferential orientations with the substrate. Furthermore, near chromium-oxide areas, an incorporation of oxygen at concentrations higher than the solubility was noted. At 830°C, this chromium oxide does not grow, because the superficial defects disappear by thermal annealing and the oxygen incorporation does not apparently depend on mechanical deformation.
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