材料期刊网

通过对有无NiCrAlY涂层镍基单晶合金进行不同温度的恒温氧化动力学曲线测定及组织结构观察,研究了纳米晶NiCrAlY涂层对高Cr单晶镍基合金高温氧化行为的影响。结果表明：在高温氧化期间,无涂层试样发生明显的氧化、内氧化和内氮化,在表层为Al2O3、Cr2O3的混合氧化物,在次表层氧化物中富含元素Ta,而元素Al贫化,并在近基体区域存在内氧化物;随氧化温度升高,元素Al的贫化区尺寸增大,其中,富Ta相可抑制基体中元素Al向外扩散,延缓合金的氧化速率。合金在氧化初期增重迅速,而恒温氧化增重动力学曲线呈现起伏波动的原因,归结于表面氧化膜的形成与剥落。高Cr单晶合金经溅射NiCrAlY纳米晶涂层,可有效改善合金的抗氧化性能;有涂层试样在不同温度的恒温氧化动力学曲线仅在氧化初期有轻微增重而后趋于平稳,其形成的Al2O3氧化膜不发生明显的剥落,仅在基体近涂层/基体界面区域存在少量AlN内氮化物。

By means of observation of microstructure and measurement of the isothermal oxidation kinetics curves,the high temperature oxidation behavior of the single crystal nickel-base superalloy with and without NiCrAlY coading was investigated.The results show that the surface oxidation,internal oxidation and internal nitridation in sub-surface layer of the uncoating superalloy occurs during oxidation at high temperature,the oxides of Al2O3 and Cr2O3 are formed on the surface layer of the alloy.The oxides with Ta-rich and Al-poor are formed in the sub-surface layer,and the internal oxides are observed in the regions near the matrix.The thickness of the Al-poor oxide layer increases as the oxidation temperature increases,thereinto,the Ta-rich phase in the oxides may restrain the element Al in the matrix diffusing outwards,which may decrease the oxidizing rate of the alloy.The mass gain of the alloy oxidized in the initial oxidation stage increases rapidly,and then the kinetics curve of the oxidation displays the undulating feature with increasing time,which is attributed to the formation and scaling off of the oxides on the surface layer.The sputtered NiCrAlY coating effectively improves oxidation resistance of the alloy,and the kinetics curve of the coating alloy displays a less mass change due to no spallation of Al2O3 film formed on the surface,and a few internal（AlN） aluminum nitrides are observed only in the region near the interface of coating and substrate.