预氧化温度对GH3128合金抗高温循环氧化性能的影响

采用热重法并结合SEM、EDAX等分析手段,研究了预氧化温度对GH3128合金抗高温(1100℃)循环氧化性能的影响。结果表明:在适当温度下进行预氧化处理可有效提高合金的抗高温循环氧化性能。GH3128合金经预氧化处理后抗高温循环氧化性能的优劣主要取决于两种因素的综合作用,其一是合金表面元素Cr的选择性氧化,形成致密均匀的保护性预氧化膜,提高合金抗高温循环氧化性能;其二是合金中元素Ti、Cr的晶界偏析加剧,加速晶界氧化并导致显微裂纹等缺陷产生,降低合金的抗高温循环氧化性能。900℃预氧化处理的GH3128合金试样具有最佳的抗高温循环氧化性能,该温度下预氧化膜形成较好且合金元素Ti、Cr的晶界偏析作用相对较弱。

Effect of Preoxidation Temperature on High Temperature Cyclic Oxidation Resistance of GH3128 Superalloy

The effect of preoxidation temperature on high temperature (1100 °C) cyclic oxidation resistance of GH3128 superalloy was studied by thermogravimetry combined with SEM, XRD and other analysis approaches. The results show that the high temperature cyclic oxidation resistance of GH3128 superalloy can be effectively improved by preoxidation at the appropriate temperature. The high temperature cyclic oxidation resistance of GH3128 superalloy after pre-oxidization depends on the combined effect of two factors. The first one is that the alloy element Cr in the surface of the alloys oxidizes selectively to form the protective oxide film, which is dense and uniform, to enhance the high temperature cyclic oxidation resistance of the alloy. The second one is that the alloy elements Ti and Cr segregate at grain boundaries in the surface of the alloys to accelerate the oxidation of grain boundary and to produce microscopic cracks near the boundary, and then reduce the high temperature cyclic oxidation resistance of the alloy. The samples pre-oxidized at 900 °C possess the best cyclic oxidation resistance due to that the protective oxide film is uniformly formed and the negative effect caused by the grain boundary segregation of Ti and Cr is relatively weak at 900 °C.