Abstract
The high-temperature oxidation of Ti1-xAlxN coatings (x = 0, 0.26, 0.45 and 0.67) deposited on 304 stainless steel by arc ion plating was investigated during initial (from 30 °C to 700 °C) and isothermal (700 °C for 12 h) oxidation in air. During initial oxidation, the oxidation rate sequence (ORS) was TiN > Ti0.33Al0.67N > Ti0.74Al0.26N > Ti0.55Al0.45N. The oxidation mechanisms of Ti1-xAlxN coatings were related to their valence electron configurations (VEC), their oxidation rates were inversely proportional to the binding energies of valence electrons and the work function of coatings. The two parameters were the intrinsic parameters of initial oxidation. During isothermal oxidation, the ORS varied with oxidation time; the final ORS was TiN > Ti0.55Al0.45N > Ti0.74Al0.26N > Ti0.33Al0.67N. Their isothermal oxidation mechanisms depended on (1) the compactness of oxide scale and Al outward diffusion; (2) the VEC of coating; (3) the electronic structures of oxide scale; (4) Al content. There were no intrinsic relationships between (1)–(3) and (4), which was the intrinsic reason for ORS of Ti1-xAlxN coatings varying with oxidation time during isothermal oxidation. The oxidation rates of Ti1-xAlxN coatings did not invariably increase and decrease with Al content during initial and isothermal oxidation, respectively.
Published Version
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