Effect of Al Content on Corrosion Resistance of (Ti1-xAlx)N Coatings under NaCl Deposit in Wet Oxygen at 600°C

(Ti1-xAlx)N(x=0, 0.1, 0.3) coatings were deposited on 1Cr11Ni2W2MoV stainless steel by arc ion plating. The (Ti1-xAlx)N coatings had B1 NaCl structure, however its preferred orientation change from (111) to (220) with the increase of Al content. A number of nodule-shaped spots identified as rutile TiO2 by XRD formed on the surface of TiN coating after corrosion beneath NaCl deposit in wet oxygen at 600 oC. With the addition of Al, a thin scale composed of Al2O3 and TiO2 formed on the surface of the (Ti1-xAlx)N coatings instead of a scale of TiO2 on TiN coating, thereby their corrosion resistance was remarkably enhanced.