Effects of Chlorate on the Hot Corrosion Behaviors of Cr0.82Al0.18N Coating Deposited on a Ti3Al Based Alloy

为了研究氯化物熔盐对Cr-Al-N涂层热腐蚀性能的影响,采用反应磁控溅射的方法在Ti3Al合金表面制备了Cr0.82Al0.18N涂层,研究了涂层在Na2SO4+25%K2SO4和Na2SO4+25%Na Cl(质量分数)2种熔盐中的热腐蚀行为,采用XRD和SEM分析了涂层热腐蚀产物的相组成和形貌。结果表明:涂层在含有氯化物盐的熔盐中腐蚀时表现为失重而在硫酸盐中腐蚀时表现为增重;Cr0.82Al0.18N涂层在2种熔盐中的腐蚀都主要由Cr2O3和θ-Al2O3组成。氯化物熔盐和腐蚀产物的挥发导致了在含有氯化物熔盐中腐蚀时的失重现象。当含有氯化物盐时会增加熔盐中氧离子的活度,从而加速Cr2O3在熔盐中的溶解。此外,热腐蚀过程中产生的氯气也会参与腐蚀反应,从而加速涂层的消耗。

Effects of Chlorate on the Hot Corrosion Behaviors of Cr0.82Al0.18N Coating Deposited on a Ti3Al Based Alloy

Cr0.82Al0.18N coating was deposited on the surface of a Ti3Al base alloy by a reactive magnetron sputtering method and the hot corrosion behaviors of this coating in Na2SO4 +25 wt% K2SO4 and Na2SO4 +25 wt% NaCl molten salt were investigated. XRD and SEM were used to analyze the phase constituents and the morphologies of the corrosion products. The results show that the sample loses its mass when corroded in sulfate and chlorate mixture molten salts while the mass increases when corroded in sulfate molten salt and the corrosion products formed in both two kinds of molten salts are mainly composed of Cr2O3 and q-Al2O3. The mass loss of the sample tested in sulfate and chlorate mixture molten salts can be explained by the easy evaporation of the chlorate molten salt and the corrosion products. The accelerated dissolution of Cr2O3 oxide scale will occur in the chlorate containing molten salt owing to the increase of the oxygen ion activity by the reaction between water vapor in the air and gas chlorine formed during the hot corrosion process. The gas chlorine will also react with the coating to form volatility metal chlorides to increase the consumption of the coating.