晶粒细化对Cr-25Nb合金高温氧化行为的影响

Effects of Grain Refinement on High Temperature Oxidation Behavior of Cr-25Nb Alloys

摘要:

采用电弧熔铸和机械合金化+热压烧结技术制备晶粒尺寸相差较大的Cr-25Nb合金，研究其在950及1200 ℃空气中的氧化行为。结果表明，熔铸态及机械合金化Cr-25Nb合金氧化后均没有发生Cr的单一外氧化，而形成了以Cr2O3为外层、NbCrO4为内层的双层氧化膜结构；机械合金化Cr-25Nb合金在950及1200 ℃的氧化速度均小于熔铸态合金，特别是在1200 ℃氧化100 h后，熔铸态Cr-25Nb合金的氧化增重是机械合金化合金的2倍多。这主要是因为晶粒细化促进了氧化膜内应力的释放，提高了氧化膜与基体的粘附性

Abstract:

In order to discuss the influence of grain refinement on the oxidation behavior of binary two-phase alloys, Cr-25Nb alloys with different grain sizes were prepared by arc-casting and mechanical alloying, and their oxidation behaviors at 950 and 1200 oC in air were investigated. The results show that in both alloys a single and continuous Cr2O3 film did not form, but a complex oxidation films occurred which contained an outer layer of Cr2O3 plus an inner layer of NbCrO4. The oxidation resistance of mechanically alloyed Cr-25Nb was higher than that of the cast alloy. In particular, the mass gain of the cast alloy is twice as much as that of mechanically alloyed alloy when they were oxidized at 1200 oC for 100 h. The differences observed above are attributed to that fine grains can accelerate the relaxation of the oxide scale stress and increase the adhesion of the oxide layer on the matrix