Abstract
Heightened interest to multicomponent alloying of nickel is connected with the search of new compositions of oxidation- and heat-resistant alloys on the basis of nickel solid solution or its intermetallics. In the present work, the author has investigated the resistance to high-temperature oxidation of an alloy of Ni – Al – Mo – W – Nb system which can be used as a basis for creation of dispersion-strengthened inert particles of carbides and nitrides of two-phase thermally stable superalloys with a γ′-phase matrix. Samples of the alloy were subjected to oxidation on air at 900 – 1300 °C during 1 – 125 hours. Weight reduction ( ΔМ , gr) was measured which after that was recalculated into indicators of change of samples weight for a time unit, rationing for the area of initial samples surface ( Δm , gr/(m 2 ·hour)) and “burn” rate of surface layer (scaling loss h, micron/hour). It is shown that at oxidation of Ni – Al – Mo – W – Nb alloy at all temperatures there is a reduction of samples weight because of formation of fragile and friable superficial scale. Dependences of this indicator on oxidation time are close to the linear. With growth of temperature, processes of weight reduction are intensified. It is offered to raise oxidation resistance of Ni – Al – Mo – W – Nb alloy by short-term preliminary oxidation at temperature of 1300 °С on air. The observable effect of increase of oxidation resistance is caused by formation in scale of NiAl 2 O 4 layer, more effectively protecting an alloy from interaction with oxygen. Experiences on oxidation with the use of inert platinum marks have shown that it is necessary to consider oxygen diffusion through oxide film into metal as a mechanism, supervising oxidation of Ni – Al – Mo – W – Nb alloy at high temperatures in case of presence of NiAl 2 O 4 on the surface layer. Activation energy of oxidation of Ni – Al – Mo – W – Nb alloy was calculated at 900 – 1300 °С and without preliminary oxidation. This value is equal to 220,000 J/mol that is characteristic for activation energy of nickel self-diffusion.
Highlights
Повышенный интерес к многокомпонентному легированию никеля связан с поиском новых составов жаропрочных и жаростойких сплавов на основе никелевого твердого раствора и его интерметаллидов
Heightened interest to multicomponent alloying of nickel is connected with the search of new compositions
the author has investigated the resistance to high-temperature oxidation of an alloy
Summary
Национальный исследовательский технологический университет «МИСиС» (Россия, 119049, Москва, Ленинский пр., 4). Образцы сплава подвергали окислению на воздухе при 900 – 1300 °С в течение 1 – 125 ч. Что при окислении сплава Ni – Al – Mo – W – Nb при всех температурах происходит уменьшение массы образцов из-за образования непрочной и рыхлой поверхностной окалины. Опыты по окислению с использованием инертных меток из платины показали, что механизмом, контролирующим окисление сплава Ni – Al – Mo – W – Nb при высоких температурах в случае наличия на поверхност и слоя NiAl2O4 , следует считать диффузию кислорода через окисную пленку вглубь металла. Рассчитана энергия активации процессов окисления образцов сплава Ni – Al – Mo – W – Nb при температурах 900 – 1300 °С и без предварительного окисления. Ключевые слова: жаростойкость, жаропрочные никелевые сплавы, нимовал, гранульная металлургия, гамма-штрих фаза, скорость окисления, энергия активации окисления, анализ по Аррениусу, самодиффузия никеля. National University of Science and Technology "MISIS" (MISIS) (4, Leninskii ave., Moscow 119049, Russian Federation)
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