镍基单晶高温合金N5及其纳米晶涂层在900℃下O_(2)和O_(2)+20%H_(2)O气氛中的氧化行为

Oxidation Behavior of a Single Crystal Ni-based Superalloy N5 and Its Nanocrystalline Coating at 900℃in O_(2)and O_(2)+20%H_(2)O Environment

以镍基单晶高温合金N5为基体,采用磁控溅射技术在基体表面沉积与其成分相同的纳米晶涂层,并对比研究合金及其纳米晶涂层在900℃下O_(2)和O_(2)+20%(体积分数)H_(2)O气氛中的氧化行为。结果表明,水蒸气加快了合金和涂层的氧化速率,促进合金表面氧化膜的剥落,并且影响了氧化膜的组成和结构。在O_(2)和O_(2)+H_(2)O环境中,合金表面氧化膜都由外层NiO、中间层NiAl_(2)O_(4)和内层Al_(2)O_(3)组成;但在O_(2)+H_(2)O环境中,合金氧化速率较大,外层氧化膜发生剥落。纳米晶涂层显著提高了合金的抗高温氧化性能,在O_(2)气氛中表面形成Al_(2)O_(3),而在O_(2)+H_(2)O气氛中表面氧化膜主要为NiAl_(2)O_(4)。同时,纳米晶涂层表面氧化膜未发生开裂和剥落,起到良好的保护作用。

The nanocrystalline coatings of superalloy N5 were deposited on the surface of nickelbased single-crystal superalloy N5 by magnetron sputtering.The oxidation behavior of the single-crystal alloy and its nanocrystalline coating in environments of O_(2) and O_(2)+20% H_(2)O at 900℃was investigated,respectively.The results show that the water vapor accelerates the oxidation rate of the bare alloy and the coating,while promotes very specially the spallation,and affects the composition and structure of the oxide scales formed on the bare alloy.Correspondingly,the formed oxide scales composed of an outer layer NiO,a middle layer NiAl2O4 and an inner layer Al_(2)O_(3) for the bare alloy being oxidized in environments of O_(2) and O_(2)+H_(2)O respectively,meanwhile,the oxidation rate is higher,and the spallation of outer oxide scale dose emerge for the oxidation in O_(2)+H_(2)O environment.The nanocrystalline coating significantly can enhance the high temperature oxidation resistance of the coated alloy.After oxidation in O_(2),Al_(2)O_(3) is formed on the surface of the coating,while in O_(2)+H_(2)O environment,the formed oxide scale is NiAl_(2)O_(4).Mean-while,no cracks and spalling were found on the surface of oxide scale,which played a good protective role.