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Indexed by:Journal Papers

Date of Publication:2019-12-01

Journal:VACUUM

Included Journals:EI、SCIE

Volume:170

ISSN No.:0042-207X

Key Words:Electron beam smelting; K417 superalloy; Oxidation behavior; Mechanism

Abstract:The high temperature oxidation behavior of electron beam smelted K417 superalloy were investigated at 800 degrees C, 900 degrees C and 1000 degrees C. The results showed that the oxidation resistance of the K417 superalloy is improved after electron beam smelting due to its resulting large grain-boundary density and low impurity content. The secondary dendrite arm spacing of K417 after electron beam smelting is approximately 42.9 mu m, which is finer than that approximately 100.0 mu m of the raw material. The O and N element contents were reduced by 50% and 67%, respectively. The oxidation kinetics were controlled by the oxidation reaction of Cr and Ti in the early stage, and subsequently it was determined by the oxidation behavior of Al. The oxide film consisted of three layers: an external layer composed of TiO2, Cr2O(3), Al2O3 and a small amount of (Ni,Co) Cr2O4; a middle layer that included TiO2, Cr2O(3), Al2O3 and trace amounts of TIVO4; and an inner layer that contained Al2O3 exclusively. An oxidation mechanism of the K417 superalloy is proposed that involves the diffusion of metal ions and O-2-at elevated temperatures.