Ta含量对镍基粉末高温合金高温氧化性能的影响

Effect of Ta Content on High Temperature Oxidation Performance of Nickel-based PM Superalloy

摘要:

采用XRD、FEG-SEM和EDS等实验技术对有不同Ta元素含量合金在800℃条件下进行抗氧化性能的研究,结果表明,含Ta合金的氧化增重和氧化时间的关系曲线符合抛物线动力学规律,氧化层为Al₂O₃+NiCr₂O₄+Ta₂O₅+(Ti/Cr)TaO₄的复合氧化物结构,而随着Ta含量的增加,氧化层厚度减小,且氧化深度变薄,氧化层也变得更加平滑而致密。实验发现,在外层和内层氧化层之间存在富Ta的氧化物(Ta₂O₅, (Ti/Cr)TaO₄),很容易与Cr₂O₃结合形成CrTaO₄,减少高温下Cr₂O₃氧化物的挥发损失,提高合金抗氧化性。实验表明：富Ta氧化物Ta₂O₅,(Ti/Cr)TaO₄的出现能阻碍金属阳离子向外扩散的速率,Ta元素的加入改变了氧化层离子扩散速率从而提高合金的抗氧化性。

Abstract:

XRD, FEG-SEM and EDS were used to study the oxidation resistance of alloys with different Ta element contents at 800℃. The results show that the relationship between oxidation weight gain and oxidation time of Ta-containing alloys conforms to parabolic kinetics law, and the oxide layer is Al₂O₃+NiCr₂O₄+Ta₂O₅+(Ti/Cr)TaO₄ composite oxide structure, and with the increase of Ta content, the thickness of the oxide layer decreases, and the oxidation depth becomes thinner, and the oxide layer becomes smoother and denser. Experiments have found that there is a Ta-rich oxide (Ta₂O₅, (Ti/Cr)TaO₄) between the outer layer and the inner oxide layer, which can easily combine with Cr₂O₃ to form CrTaO₄, which reduces the volatilization loss of Cr₂O₃ oxide at high temperatures and improves the oxidation resistance of the alloy. Experiments show that Ta-rich Ta₂O₅ and (Ti/Cr)TaO₄ can hinder the out-diffusion rate of metal ions. The addition of Ta changes the ion diffusion rate of the oxide layer and improves the oxidation resistance of the alloy.