文章信息/Info

Title:

Preparation Technologies and Modified Silicide Oxidation-resistant Coatings of Nb-Si Based Ultrahigh Temperature Alloy

作者:

郭喜平

西北工業大學凝固技術國家重點實驗室，陜西 西安 710072

Author(s):

GUO Xiping

State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China

關鍵詞:

Nb-Si基超高溫合金; 合金化; 制備技術; 抗氧化滲層; 改性硅化物

DOI:

10.7502/j.issn.1674-3962.2015.02.03

文獻標志碼:

A

摘要:

Nb-Si基超高溫合金具有高熔點、適中的密度以及良好的高低溫力學性能，有潛力應用于1200—1450℃，但其抗氧化性能較差。本文綜述了該合金的成分特點、制備方法，特別是其抗氧化硅化物滲層的制備方法、組織特點及其氧化行為。合金的制備方法主要有真空電弧熔煉、定向凝固、粉末冶金、蒸發沉積、沖擊波合成及感應凝殼熔煉等。開發了Al, Y, Cr, B, Ce, Zr, Ge等單元以及多元聯合改性的NbSi2基硅化物涂層體系，其中多種涂層體系經1250～1350℃恒溫氧化100～200 h或1250℃～室溫循環氧化100次后仍對基體合金具有優異的保護能力。Al對滲層氧化行為的改性體現于對氧化膜組織結構的影響，也即合適的Al含量可促使在滲層(Nb,X)Si2外層的表面優先生成SiO2，從而形成以SiO2?Al2O3為主的致密氧化膜。

Abstract:

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 1200—1450℃. 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. Several methods can be adopted to prepare the alloys, such as vacuum arc melting, directional solidification, powder metallurgy, evaporate deposition, shock synthesis, and induction skull melting. 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 1250-1350℃ for more than 200 h or cyclic oxidation at 1250℃-room temperature for more than 100 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 SiO2 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.