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Beneficial and detrimental Effects of Nitrogen on the oxidation behaviour of TiAl‐based intermetallics
Author(s) -
Schaaf P.,
Quadakkers W. J.,
Zheng N.,
Wallura E.,
Gil A.
Publication year - 1997
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.19970480106
Subject(s) - nitrogen , oxide , materials science , intermetallic , nitride , isothermal process , aluminium , alloy , titanium aluminide , metallurgy , ternary operation , titanium , aluminide , aluminium alloy , chemical engineering , layer (electronics) , chemistry , thermodynamics , composite material , physics , organic chemistry , computer science , engineering , programming language
The isothermal oxidation of binary and ternary, Nh‐containing titanium aluminides was studied at 900°C in air and Ar/O 2 . It was found that the presence of nitrogen in the atmosphere is in some cases beneficial, in others detrimental. For an interpretation of the effects of nitrogen it is necessary to consider the various oxidation stages in which the mechanisms of titanium aluminide oxidation fundamentally differ. For High‐Al alloys, which tend to form protective alumina based scales in the early oxidation stages, nitrogen always scenes to he detrimental because it promotes the formation of a more rapidly growing mixed alumina/titania scale. After this shift to mixed oxide scales, nitrogen can be detrimental as well as beneficial. It is proposed that the last mentioned case prevails if a near‐continuous Ti‐rich nitride layer is stable at the oxide/alloy interface, thereby preventing internal oxidation of aluminium. This beneficial effect, of nitrogen was found under all studied conditions for the Nb‐containing alloys but only in some cases for the binary alloys.