Mo-TiC金属陶瓷的高温抗氧化行为及机理

采用粉末冶金法制备Mo-TiC金属陶瓷,研究不同TiC含量的Mo-TiC陶瓷在1 200℃下的氧化行为,并测定该陶瓷氧化前后的抗弯强度。结果表明,随TiC含量增加,Mo-TiC金属陶瓷的高温抗氧化能力增强,Mo-40%TiC和Mo-60%TiC在1 200℃下氧化60 min后质量损失率分别为23.91%和4.79%。氧化从陶瓷基体表面缺陷和晶界处开始,逐步向内部侵蚀。陶瓷中的钼被氧化生成易挥发的MoO3,TiC被氧化生成TiO2,TiO2颗粒在陶瓷表面形成连结紧密的片层状组织,延缓氧化行为向基体内部侵蚀,而且随TiC含量提高,这种效果愈明显。Mo-TiC金属陶瓷的抗弯强度随TiC含量增加而降低,氧化后抗弯强度明显下降。Mo-40%TiC在氧化前抗弯强度为502 MPa,而在氧化之后降到160 MPa。Mo-TiC陶瓷氧化后的抗弯强度随TiC含量增加而略有升高。

Oxidation behavior and mechanism of Mo-TiC cermet at high temperature

Mo-TiC cermets have been prepared by powder metallurgy process.The oxidation behaviors of Mo-TiC cermet at 1 200 ℃ were studied.The bending mechanical properties of Mo-TiC cermet before and after oxidation were compared.The results indicate that high temperature anti-oxidation property of Mo-TiC cermet improves with increasing the TiC content.After oxidized at 1 200 ℃ for 60 min,the mass loss ratio of Mo-40%TiC and Mo-60%TiC cermets are 23.91% and 4.79%,respectively.The oxidation of Mo-TiC cermet begins at defects or grain boundaries,and then corrades into the inside and ambient area gradually.Molybdenum is oxidized to volatile MoO3 and TiC is oxidized to TiO2.TiO2 particles can form a densification sheet-layered structure on the surface of ceramic.The sheet-layered strucrure can obstruct the intrusion of oxygen to the substrate,and this effect will be enhanced with increasing TiC content in the cermet.The bending strength of Mo-40%TiC is 502 MPa before oxidation,but reduces to 160MPa after oxidation.The bending strength after oxidation of Mo-TiC cermet slightly increases with increasing TiC content.