摘要
研究了不同体积分数原位合成SiC颗粒增强MoSi2基复合材料在900℃空气中1000 h的长期氧化行为.复合材料氧化1000 h后,均未发生pest现象. 6种材料都表现出优异的氧化抗力,原位合成的复合材料的氧化抗力好于传统的通过热压商用MoSi2粉末和Si C粉末混合物制备的复合材料(外加复合材料).复合材料氧化膜表层为连续致密的α-SiO2(α-石英),下层为Mo5Si3,复合材料的氧化过程不仅是O2与MoSi2的作用,SiC也同时发生了氧化.材料900℃下发生硅的选择性氧化,正是这种硅的选择性氧化在MoSi2的表面自发形成一层致密的SiO2保护膜,使材料表现出优异的长期氧化抗力.
MoSi2 intermetallic is well known as one of the most promising compounds used as structural components due to its high melting point,relatively low density,excellent oxidation resistance,and good strength at high temperatures.Unfortunately,MoSi2 has poor toughness at low temperatures and low creep strength at elevated temperatures.Especially,MoSi2 alloy usually exhibits severe'pest oxidation'at low temperatures of between 400 and 900℃.These problems limit the applications of MoSi2 alloys.The main methods to solve these problems are alloying and compounding.Unfortunately,so far,the problem of low-temperature oxidation resistance of MoSi2 has not been completely solved,and its composite materials are reinforced using external means.In a previous work,Si C particle-reinforced MoSi2 matrix composites were prepared by an in situ synthesis technique,and the microstructures and the mechanical behaviors at room temperature and high temperature were systematically studied.In this work,the long-term oxidation behavior of in situ synthesized Si C particulate-reinforced MoSi2 matrix composites with different volume fractions and occurring at 900℃for 1000 h was investigated.The composites are not observed to disintegrate(pest)after oxidation for 1000 h.The oxidation resistances of six kinds of materials appear excellent.The composite synthesized by in situ possesses higher oxidation resistance than the traditional composite,which is fabricated by hot-pressing the mixture of commercial powders of MoSi2 and Si C.The surface of scales consists ofα-SiO2(α-quartz),and the subsurface is composed of Mo5Si3.The oxidation of the composites is conducted not only between MoSi2 and O2,but also Si C is oxidized.Selective oxidation of Si completely takes place at 900℃.This selective oxidation results in the spontaneously formation of a layer of dense Si O2 protective scale on the MoSi2 surface,making the material exhibit excellent long-term oxidation resistance.
作者
王超
段立辉
张来启
WANG Chao;DUAN Li-hui;ZHANG Lai-qi(School of Materials and Metallurgy,Inner Mongolia University of Science and Technology,Baotou014010,China;State Key Laboratory for Advanced Metals and Materials,University of Science and Technology Beijing,Beijing100083,China)
出处
《工程科学学报》
EI
CSCD
北大核心
2019年第9期1168-1175,共8页
Chinese Journal of Engineering
基金
国家自然科学基金资助项目(51871012)
金属材料磨损控制与成型技术国家地方联合工程研究中心开放课题资助项目(HKDNM201805)
作者简介
通信作者:张来启,E-mail:zhanglq@ustb.edu.cn
