稀土改性Fe-Al层表面Al_(2)O_(3)薄膜的物相分布

Phase Distribution of Al_(2)O_(3)Thin Films on Rare Earth-Modified Fe-Al Layer Surface

在760℃下采用稀土改性包埋渗铝以及原位氧化方法制备Fe-Al/Al_(2)O_(3)复合涂层,研究了渗铝层和氧化膜的微观组织和相分布。结果表明,稀土改性渗铝层可分为3层:外层渗铝层、过渡层和内扩散层。渗铝层主要由FeAl相和Fe_(3)Al相组成。FeAl相主要集中在渗铝层的外层,为Al_(2)O_(3)氧化膜的选择性氧化提供了有利条件。氧化膜表面呈α-Al_(2)O_(3)脊状结构。此外,表面氧化铈的存在是由于氧化初期Ce向外扩散且与O2的优先反应。氧化膜可分为2层,即纯α-Al_(2)O_(3)层和主要由α-Fe(Al)和Al、Fe、Ce的混合氧化物组成的过渡层。

Fe-Al/Al_(2)O_(3)composite coating was prepared through rare earth-modified aluminizing and in-situ oxidation at 760℃.The microstructure and phase distribution of the aluminizing layer and oxide film were investigated.Results show that the rare earthmodified aluminizing layer can be divided into three layers:an outer aluminizing layer,a transition layer,and an inner diffusion layer.The aluminizing layer is predominantly composed of FeAl phase and Fe_(3)Al phase.Notably,the FeAl phase is primarily concentrated in the outer layer of aluminizing layer,providing favorable conditions for selective oxidation of the Al_(2)O_(3)oxide film.The surface of oxide film exhibits theα-Al_(2)O_(3)ridge structure.Additionally,the presence of Ce oxide on the surface is attributed to the outward diffusion of Ce and its preferential reaction with O2 during the initial oxidation stage.The oxide film can be divided into two layers,namely a pureα-Al_(2)O_(3)layer and a transition layer which is mainly composed ofα-Fe(Al)and mixed oxides of Al,Fe,and Ce.