High-temperature oxidation resistance of sputtered (Al,Cr,Nb,Ta,Ti,Si)N coatings

• Published in: Journal of alloys and compounds Vol. 1010; p. 176912
• Main Authors: Kretschmer, Andreas, Mayrhofer, Paul Heinz
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.01.2025
• Subjects: A ceramic; A sputtered films; B SEM; B TEM; B XRD; C oxidation; A ceramic; B SEM; B XRD; C oxidation; A sputtered films; B TEM
• ISSN: 0925-8388
• DOI: 10.1016/j.jallcom.2024.176912

High-entropy metal-sublattice (Al,Cr,Nb,Ta,Ti)N coatings, with up to 15.0 at% additional Si content were developed and investigated for their oxidation resistance by exposing them for 3, 30, and 100 h to ambient air at 900, 950, and 1000 ∘C. The Si-free coating is rapidly oxidized, but all of the Si-alloyed coatings survive even the harshest oxidation test. The oxides crystallize mostly in the rutile structure with some Ta2O5-type phase fractions at higher Si contents. Detailed TEM investigations reveal a varied microstructure across the oxide scales with a succession of Cr-, Al, and Ti-rich top oxide layers, which agrees with a reported thermodynamical calculation of oxide stabilities. [Display omitted] •We oxidized (Al,Cr,Nb,Ta,Ti,Six)N coatings for up to 100 h.•The Si-free coating fails at 950 ∘C.•The Si-alloyed coatings all survive 100 h at 1000 ∘C.•The most protective coating has amorphous grain boundary regions in the oxide scale.•The succession of oxide layers at the surface agree with a thermodynamical model.