简单/改性铝化物涂层的研究现状

航空发动机各部件高温结构材料在苛刻环境下服役时,会遭受严重的高温氧化和热腐蚀.在合金表面施加铝化物涂层后,高温下表面能够生成一层致密且生长缓慢的Al2O3氧化膜,从而隔绝腐蚀介质,以防止合金被快速氧化腐蚀.概述了铝化物涂层的优点,包括制备简单、成本低廉.重点综述了以Ni、Fe、Ti/TiAl为合金基体的铝化物涂层微观结构.涂层的微观结构主要由渗铝工艺、基材成分及后处理工艺等因素决定,渗铝工艺包括渗剂成分、渗铝温度和渗铝时间.在高温下渗铝,Al的活度较低,涂层主要以基体元素向外扩散形成外扩散型涂层为主;在低温下渗铝,Al的活度较高,涂层主要以Al向内扩散形成内扩散型涂层为主.还归纳了不同渗铝涂层在干燥空气和水蒸气环境中的高温氧化行为,阐述了水蒸气对铝化物涂层高温氧化行为的影响,比较了Ni-Al系和Fe-Al系涂层的抗高温氧化性能.同时介绍了Cr-Al、Si-Al和Pt-Al 3种改性铝化物涂层的研究进展,包括制备方法、微观结构及抗高温氧化和腐蚀性能.最后,展望并总结了高温防护涂层的发展趋势.

Current Research Status of Simple/Modified Aluminide Coatings

The high temperature structural materials of various parts of aero-engine will suffer from serious oxidation and hot corrosion when they are in service under harsh environment. A dense and slow-growing Al2O3 scale, which can segregate the corrosive medium and prevent the matrix alloy from rapid oxidation and corrosion, is formed on the surface of aluminide coatings at high temperature when aluminide coatings are applied on alloys. The advantages of aluminide coating, including simple preparation and cost-effective, are summarized. The microstructures of aluminide coatings formed on Ni-based, Fe-based and Ti/TiAl-based alloys are mainly reviewed. The microstructure of the coating mainly depends on the aluminisation process, the composition of the substrate and the post-treatment process. Among them, the aluminisation process includes the composition of aluminisation agent, aluminisation temperature and aluminisation duration. Aluminisation temperature plays an important role in the structure of coatings. At high temperature, the activity of Al is low, and the coating is formed mainly by outward-diffusion of the matrix elements. But at low temperature aluminizing, the activity of Al is higher, and coating is formed mainly by Al inward-diffusion. The oxidation behaviour of different aluminide coatings in dry and steam atmosphere at high temperature is also concluded, and the effect of water vapour on the oxidation behaviour of aluminide coatings is described. The high-temperature oxidation resistance of Ni-Al and Fe-Al coatings are compared. The research progress of three kinds of modified aluminide coatings, i.e. Cr-Al, Si-Al and Pt-Al coatings is introduced meanwhile, including preparation method, the microstructure and high-temperature oxidation resistance. Finally, the development trend of high temperature protective coating is prospected and summarized.