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 Superalloys

采用XRD、FEG-SEM和EDS等实验技术对不同Ta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规律,氧化层为Al_(2)O_(3)+NiCr_(2)O_(4)+Ta_(2)O_(5)+(Ti/Cr)TaO_(4)的复合氧化物结构,而随着Ta含量的增加,氧化层厚度减小,且氧化深度变浅,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(Ta_(2)O_(5),(Ti/Cr)TaO_(4)),很容易与Cr_(2)O_(3)结合形成CrTaO_(4),从而减少高温下Cr_(2)O_(3)氧化物的挥发损失,提高合金的抗氧化性能。富Ta氧化物Ta_(2)O_(5),(Ti/Cr)TaO_(4)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了合金的抗氧化性能。

The oxidation resistance of superalloys(FGH98) with different Ta element contents at 800 ℃ was studied by XRD, FEG-SEM and EDS.The results show that the relationship between oxidation mass gain and oxidation time of Ta-containing alloys conforms to parabolic kinetics law,and the oxide layer is Al_(2)O_(3)+NiCr_(2)O_(4)+Ta_(2)O_(5)+(Ti/Cr)TaO_(4) composite oxide structure. With the increase of Ta content, the thickness of the oxide layer decreases, the oxidation depth becomes thinner, and the oxide layer becomes smoother and denser. There is a Ta-rich oxide(Ta_(2)O_(5),(Ti/Cr)TaO_(4))between the outer layer and the inner oxide layer, which can easily combine with Cr_(2)O_(3)to form CrTaO_(4), which reduces the volatilization loss of Cr_(2)O_(3) oxide at high temperatures and improves the oxidation resistance of the alloy. The appearance of Ta-rich Ta_(2)O_(5)and(Ti/Cr)TaO_(4) can hinder the out-diffusion rate of metal ions. The addition of Ta changes the ion diffusion rate of the oxide layer, improving the oxidation resistance of the alloy.