摘要
利用连续沉积的包埋渗法,在钼表面制备了(Ti,Mo)Si_(2)/MoSi_(2)复合涂层。利用X射线衍射、扫描电子显微镜、能谱仪和热力学计算对涂层进行了表征与反应机理分析。结果表明,共沉积法无法实现Ti的有效沉积。先渗Ti、再渗Si的两步沉积工艺能有效制备Ti改性硅化物涂层。涂层分为3层,最外层为(Ti,Mo)Si_(2)三元化合物层,次外层为MoSi_(2)层,次外层与基体间为Mo;Si_(2)过渡层。渗硅温度对涂层结构无明显影响。Ti改性硅化物涂层的生长速率略低于单一渗硅涂层的生长速率。(Ti,Mo)Si_(2)/MoSi_(2)复合涂层的形成由Ti、Si内扩散控制。Ti元素集中在涂层表层,Si元素通过(Ti,Mo)Si_(2)化合物层与基体作用形成MoSi_(2)层和Mo;Si_(2)过渡层。渗Ti过程中,埋渗料间反应会引入游离态铝氟化物AlF;。在随后的渗硅过程中,游离态Al以Al;Mo的形式在(Ti,Mo)Si_(2)层中靠近MoSi_(2)层的上界面处析出。在1200℃周期性氧化过程中,(Ti,Mo)Si_(2)/MoSi_(2)复合涂层持续循环氧化180 h后未出现明显失重。(Ti,Mo)Si_(2)层氧化形成的SiO;与TiO;致密复合氧化层能填充涂层表面裂纹,持续阻碍氧扩散,因此其在周期性氧化环境下的抗氧化性能显著优于单一渗硅涂层。
(Ti,Mo)Si_(2)/MoSi_(2) composite coatings were prepared on Mo substrate by the continuous deposition pack cementation method.The X-ray diffraction(XRD),scanning electron microscope(SEM),energy dispersive spectroscopy(EDS),and thermodynamic calculation were used to characterize the composite coatings and to analyze the formation mechanism.The results show that the co-deposition process cannot achieve the titanium deposition effectively.The titanium-modified MoSi_(2) coatings can be prepared by a two-step deposition process of titanizing and siliconizing.The coatings contain three layers:the outer layer is(Ti,Mo)Si_(2) ternary compound layer;the second layer is MoSi_(2) layer;the layer between the MoSi_(2)and Mo substrate is the Mo;Si_(2)transition layer.The siliconizing temperature shows negligible effect on coating structure.The growth rate of titanium-modified MoSi_(2)coating is slightly lower than that of single MoSi_(2)coating.The growth of(Ti,Mo)Si_(2)/MoSi_(2)composite coating is dominated by the inward diffusion of Ti and Si.Ti is concentrated on the outer layer of the coating.Si diffuses through the(Ti,Mo)Si_(2)compound layer and interacts with the substrate to form the MoSi_(2)layer and Mo;Si_(2)transition layer.In the titanizing process,the free state AlF;is introduced by the reaction among pack mixtures.In the subsequent siliconizing process,a trace amount of Al in free state is precipitated in the form of Al;Mo phases in the(Ti,Mo)Si_(2)layer near the upper interface of MoSi_(2)layer.During the cyclic oxidation tests at 1200℃,the(Ti,Mo)Si_(2)/MoSi_(2)composite coatings do not lose mass obviously after exposure in oxidation atmosphere for 180 h.A dense composite oxide layer consisting of SiO;and TiO;can be formed by the oxidation of(Ti,Mo)Si_(2)phase.This composite oxide layer can fill the surface cracks of the coating and continuously block the oxygen diffusion,so the oxidation resistance of(Ti,Mo)Si_(2)/MoSi_(2)composite coating in the periodic oxidation environment is far superior to that of the si
作者
何浩然
刘奇
薄新维
王小宇
王焱辉
姚志远
韩校宇
刘成超
He Haoran;Liu Qi;Bo Xinwei;Wang Xiaoyu;Wang Yanhui;Yao Zhiyuan;Han Xiaoyu;Liu Chengchao(Chongqing Materials Research Institute Co.,Ltd,Chongqing 400707,China;National Engineering Research Center for Instrument Function Materials,Chongqing 400707,China;School of Chemistry and Chemical Engineering,Chongqing University of Technology,Chongqing 400054,China)
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2021年第11期3828-3836,共9页
Rare Metal Materials and Engineering
基金
Sponsored by Basic Research and Frontier Exploration of Chongqing(cstc2019jcyj-msxm X0795)
Major Science and Technology Projects of Nuclear Power(2017ZX06004004)
Technology Innovation and Application Demonstration Project of Beibei(2020-4)。
关键词
包埋渗
钼硅化物
钛改性
抗氧化
pack cementation
molybdenum disilicide
titanium modification
anti-oxidation