The subject of this work is the influence of thermal cycles under the conditions of the high vacuum on chemical and elementary composition of surface layers of metallic materials for the space vehicles. Changes of the elementary composition during thermal cycling were recorded by Auger spectrometry and X-ray-electron-spectrometry. Investigations were performed on samples of 12Kh18N10T steel and VT-1-0 alloy. The samples were heated up to 453K and cooled to 123K at the pressure of 10 exp(-7)-10 exp(-8)Pa. Formation of the lower oxides of the elements, which are present in the materilas composition, was found in the both materials. It was shown that decomposition of the higher oxides occurs during thermal cycles and the most resistant were compounds with less oxygen (of Me2O type). Thermal cycling was found to promote the interstitial elements migration along the intergranular spacings into metal bulk, which leads to metal failure. The greatest homogenization of metal was achieved by number of thermal cycles three. The following mechanism of the impurity elements sorption has been proposed. The thermal cycling process is accompanied by an active penetration of oxygen into the metal bulk, which induces a stessed state in this zone and facilitaties the penetration of other impurities (carbon, chloride, sulphur, calcium, sodium) into these regions.
Features of chemical elements migration in the near-surface layers of metals and alloys during thermal cycling
Eigenschaften der Wanderung von chemischen Elementen in die Oberflächenschichten von Metallen und Legierungen bei thermischer Wechselbeanspruchung
1996
10 Seiten, 3 Bilder, 3 Tabellen, 10 Quellen
Aufsatz (Konferenz)
Englisch
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