Y_2O_3含量对机械合金化Ni-20Cr-2.5Al合金热腐蚀行为的影响

Effect of Y_2O_3 Content on Hot Corrosion Behavior of Mechanical Alloyed Ni-20Cr-2.5Al Alloy

采用机械合金化及热压法制备Ni-20 Cr-2.5Al、Ni-20 Cr-2.5 Al-0.8 Y2O3和Ni-20 Cr-2.5Al-3Y2O3高温合金,研究了不同含量Y2O3对Ni-20 Cr-2.5 Al合金在900℃空气中热腐蚀行为的影响。结果表明:Ni-20 Cr-2.5 Al合金在高温热腐蚀的实验初期有氧化膜剥落现象发生,而Ni-20 Cr-2.5 Al-0.8 Y2O3和Ni-20 Cr-2.5Al-3 Y2O3两种合金变化比较轻微;三种合金在氧化初期氧化增重比较明显,后期增重缓慢,涂有盐膜的Ni-20Cr-2.5Al合金的氧化增重最大,Ni-20Cr-0.8Y2O3合金次之,Ni-20Cr-2.5Al-3Y2O3合金的氧化增重最小。热腐蚀后三种合金表面的腐蚀膜分为两层,氧化膜外层主要由Al2O3组成,内层主要由靠近基体的Cr2O3组成,且Cr2O3腐蚀膜的厚度很薄。Y2O3的添加能够起到净化界面的作用,不仅提高了界面结合强度,也使得Al2O3保护膜具有更微小的晶粒,因而提高合金的抗热腐蚀性能。

Ni-20Cr-2.5Al, Ni-20Cr-2.5Al-0.8Y2O3 and Ni-20Cr-2.5Al-3Y2O3 alloys were prepared by mechanical alloying and hot pressing. The effect of Y2O3 content on hot corrosion behavior of mechanical alloyed Ni-20Cr-2.5Al alloy at 900 ℃ in air was investigated. The results show that, oxide film spalling of Ni-20Cr-2.5Al alloy has occurred in the early experiments of high temperature hot corrosion, while Ni-20Cr-2.5Al-0.8Y2O3 and Ni-20Cr-2.5Al-3Y2O3 alloys have relatively minor change; and all of them gain weight obviously in the early oxidize, the oxidation weight-increment of Ni-20Cr-2.5Al alloy is the highest, and Ni-20Cr-2.5Al-0.8Y2O3 alloy is the second, Ni-20Cr-2.5Al-3Y2O3 alloy is the lowest. The corrosion film of the three kinds of alloys includes two layers, the outside layer is mainly Al2O3 and the inside layer is mainly Cr2O3 which is a thin film. Besides, Y2O3 can play a role in purifying the interface; it not only can improve the interfacial bond strength, but also can make Al2O3 protective film have smaller micro-grain, so adding Y2O3 can increase the hot corrosion resistance of the alloy.