渗氮层对GH901合金在700℃下氧化行为的影响

Effect of nitrided layer on oxidation behavior of GH901 alloy at 700℃

采用扫描电镜(SEM)、能谱仪(EDS)、X射线衍射(XRD)等研究了GH901合金未渗氮试样和渗氮试样在700℃空气中的氧化行为。结果表明:未渗氮试样氧化动力学曲线遵循抛物线规律,渗氮试样符合直线规律。未渗氮试样基体表面由单一的Cr_(2)O_(3)和(Cr_(0.88)Ti_(0.12))2O_(3)氧化层组成,氧化层表面有少量TiO_(2)生成,氧化过程由氧向内扩散和Cr、Ti向外扩散控制。渗氮试样由于渗氮层CrN、TiN相的出现使得合金氧化机理发生转变,氧化速率显著增加,表面氧化层呈现3层结构:Fe_(2)O_(3)外层、NiFe_(2)O_(4)内层、Ti-Cr混合氧化物组成的内氧化区,氧化过程由氧向内扩散和Fe、Ni向外扩散控制。

The oxidation behavior of GH901 alloy sample without and with nitrided layer in air at 700℃was studied by means of scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS)analysis and X-ray diffraction(XRD).The results show that the oxidation kinetics curve of the non nitrided sample follows the parabolic law,and the nitrided sample follows the linear law.The substrate surface of the non nitrided sample is composed of a single Cr_(2)O_(3)and(Cr_(0.88)Ti_(0.12))2O_(3)oxide layer,a small amount of TiO_(2)is formed on the surface of the oxide layer,and the oxidation process is controlled by the inward diffusion of oxygen and the outward diffusion of Cr and Ti.The appearance of CrN and TiN phases in the nitrided layer makes the oxidation mechanism of the alloy change,and the oxidation rate increases significantly.The surface oxide layer presents a three layer structure:the outer layer of Fe_(2)O_(3),the inner layer of NiFe_(2)O_(4),and the internal oxidation zone composed of Ti-Cr mixed oxides.The oxidation process is controlled by the inward diffusion of oxygen and the outward diffusion of Fe and Ni.