摘要
Nb-Si基超高温合金具有高熔点、适中的密度、良好的高低温力学性能等特征,有潜力应用于1200-1 450℃高温,但其抗氧化性能较差。综述了该合金的成分特点、制备方法、特别是其抗氧化硅化物渗层的制备方法、组织特点及其氧化行为。重点介绍了该合金的整体定向凝固方法及其组织特点。开发了Al,Y,Cr,B,Ce,Zr,Ge等单元以及多元联合改性的NbSi2基硅化物涂层体系,其中多种涂层体系经1250-1350℃恒温氧化100-200 h或1 250℃-室温循环氧化100次后仍对基体合金具有优异的保护能力。其中最具有代表性的是采用Si-Al-Y2O3包埋共渗在Nb-Si基超高温合金表面制备的Y,Al二元联合改性硅化物渗层。Al对渗层氧化行为的改性体现于对氧化膜组织结构的影响,即合适的Al含量可促使在渗层（Nb,X）Si2外层的表面优先生成SiO2,从而形成以SiO2·Al2O3为主的致密氧化膜。
Nb-Si based ultrahigh temperature alloys possess higher melting points,relatively lower densities and attractive high temperature strength,and therefore,they have been expected to be employed in the temperature range of 1 200 -1 450 ℃. However,their oxidation resistant performance has not been good enough for the actual application in oxidizing environments. In this paper,the composition,preparation technologies and the silicide oxidation-resistant coatings of the alloys have been introduced. It mainly introduces the whole directional solidfication method and structure characteristics of the alloy.Many NbSi2-type oxidation-resistant coatings modified with single or multi-elements including Al,Y,Cr,B,Ce,Zr and Ge have been developed for the alloys,and some of them exhibit excellent protection performance for the alloys and can endure isothermal oxidation at 1 250 - 1 350 ℃ for more than 200 h or cyclic oxidation at 1 250 ℃ - room temperature for more than100 cycles. The addition of Al in the coatings has a significant effect on the structure of the scales formed on the coatings upon oxidation. The existence of a suitable content of Al in the coatings could promote the formation of Si O2 preferentially on the surface of the（ Nb,X） Si2 outer layer of the coatings,and thus forming a dense and compact scale mainly consisting of SiO2·Al2O3.
出处
《中国材料进展》
CAS
CSCD
北大核心
2015年第2期120-125,135,共7页
Materials China
基金
国家自然科学基金资助项目(510717124
51371145
51431003
U1435201)
关键词
Nb-Si基超高温合金
合金化
制备技术
抗氧化渗层
改性硅化物
包埋共渗
Al
定向凝固
Nb-Si based ultrahigh temperature alloy
alloying effect
preparation technologies
oxidation-resistant coating
modified silicide coating
diretional solidification
Al
pack cementation
