Co/Pt改性铝化物涂层热腐蚀行为探究及比较

Study and Comparison of the Hot Corrosion Behavior of Co/Pt Co-Modified Aluminide Coating

摘要:

为提高镍基单晶高温合金的抗热腐蚀性能，采用电镀/高温气相渗铝的方法，在合金基体表面分别制备了铝化物涂层、Co改性铝化物涂层和Co/Pt共改性铝化物涂层。将涂层样品置于Na₂SO₄/NaCl（质量百分比75∶25）混合盐中进行了900 ℃热腐蚀实验，利用XRD和SEM/EDS等方法研究了三种涂层样品的热腐蚀行为，同时还研究了Co和Pt元素对涂层抗热腐蚀性能的影响。实验结果表明：900 ℃热腐蚀100 h后，铝化物涂层的质量增重为4.07 g·cm^-2，Co改性铝化物涂层质量增重为0.74 g·cm^-2，Co/Pt共改性铝化物涂层的质量增重为5.96 g·cm^-2；Co/Pt共改性铝化物涂层无明显剥落，氧化膜相对完整，说明其抗热腐蚀性能最好，而另两种涂层则出现明显剥落，说明二者抗热腐蚀性能均较差。Co/Pt的协同作用，促进了涂层表面保护性Al₂O₃膜的形成，提高了氧化膜的粘附性和自修复性，増大了涂层的钝化范围，降低了涂层外部的S及O等元素的向内扩散速度。

Abstract:

To improve the hot corrosion resistance of nickel-based single crystal superalloy， aluminide coating， Co-modified aluminide coating and Co/Pt co-modified aluminide coating were deposited on its surface by electroplating and high temperature vapor aluminizing. The coating samples were subsequently placed in Na₂SO₄/NaCl （75∶25， wt./wt.） mixed salt at 900 ℃ for hot corrosion experiments. XRD and SEM/EDS techniques were used to study their hot corrosion behavior， meanwhile， the effects of Pt and Co elements on the hot corrosion resistance of coatings were investigated. The experimental results show that after hot corrosion in Na₂SO₄/NaCl （mass percentage 75∶25） mixed salt at 900 ℃ for 100 h， the mass gain of ordinary aluminide coating is 4.07 g·cm^-2， that of Co-modified aluminide coating is 0.7478 g·cm^-2， and the Co/Pt co-modified aluminide coating has a mass gain of 5.96 g·cm^-2. The Co/Pt co-modified aluminide coating shows no obvious peeling and the oxide film is relatively complete， indicating its highest thermal corrosion resistance. While， the other two coatings have obvious peeling， indicating that the thermal corrosion resistance of both is poor. The synergistic effect of Co/Pt addition promotes the formation of protective Al₂O₃ film on the surface of the coating， improves the adhesion and self-healing of the oxide film， increases the passivation range of the coating， and reduces the inward diffusion rate of S and O elements outside the coating.