Microstructure and corrosion resistance of Hf-modified NiAl layers on nickel based superalloy Ni-Cr-Co-Mo-2Ti-1.5Al

ABSTRACT: Article discusses examination of aluminizing and Hf modification impact on the microstructure and corrosion resistance of manufactured layers with use of CVD method on a substrate of nickel based superalloyNi-Cr-Co-Mo-2Ti-1.5Al. The effect of modification process on microstructure, phase and chemical composition and corrosion resistance of manufactured layers was examined. Corrosion resistance of base material and material with protective layers was also compared. The effect of Hf modifications on surface morphology and thickness of layers and corrosion resistance of substrate was demonstrated.

KEYWORDS: superalloy, NiAl layer, intermetallic layer, oxidation, layer modification, microstructure, corrosion resistance, phase composition.

STRESZCZENIE: Warstwy ochronne na bazie międzymetalicznej fazy NiAl stosowane są powszechnie do poprawy odporności na utlenianie wysokotemperaturowe odpowiedzialnych elementów turbin silników lotniczych. W pracy omówiono wyniki badań właściwości warstw NiAl oraz warstw NiAl modyfikowanych Hf oraz ich wpływu na mikrostrukturę podłoża - nadstopu niklu Ni-Cr-Co-Mo-2Ti-1,5Al. Procesy aluminiowania realizowano metodą CVD w atmosferze wodoru jako gazu nośnego. Przeprowadzono obserwacje mikrostruktury warstw oraz podłoża, badania składu chemicznego i fazowego warstw. Stwierdzono, że wytworzone warstwy wykazują ciągłość na całej powierzchni próbek, stabilność składu chemicznego i fazowego oraz nie wpływają na mikrostrukturę stopu.

SŁOWA KLUCZOWE: nadstop, warstwa NiAl, warstwa na bazie fazy międzymetalicznej, utlenianie, modyfikacja warstwy, mikrostruktura, odporność korozyjna, skład fazowy.

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DOI: http://dx.doi.org/10.17814/mechanik.2015.2.96