常压化学气相沉积ZrC涂层动力学与组织结构

摘要

以ZrCl4-CH4-H2-Ar为反应体系,采用常压化学气相沉积(APCVD)法在1 473～1 873 K制备ZrC涂层,用X线衍射和扫描电镜分析涂层的相成分、ZrC晶粒择优生长及微观形貌,研究ZrC涂层沉积动力学和涂层组织结构.研究结果表明:随沉积温度的升高,APCVD ZrC涂层的沉积速率增大,ZrC微晶表观尺寸也相应增大;1 473～1 673 K沉积时,化学气相沉积过程的表观活化能为71.69 kJ/mol,沉积过程由化学动力学控制;1 673～1 873 K沉积时,过程的表观活化能为14.28 kJ/mol,沉积过程由扩散控制.沉积温度由1 473 K上升至1 673 K时,ZrC晶粒的择优生长取向出〈220〉转变为〈200〉,ZrC涂层组织为典型的针状晶结构,涂层较疏松、粗糙;1 873 K沉积时,ZrC晶粒呈短柱状,ZrC涂层致密平整,且沉积速率最高.%ZrC coating was prepared by atmospheric pressure chemical vapor deposition (APCVD) with ZrCl4-CH4-H2-Ar chemical system at different temperatures. X-ray diffractometry (XRD) and scanning electron microscopy (SEM) were used to analyze phase composition, crystalline preferred orientation, and micro-morphology of ZrC coating. The influences of temperature on deposition kinetics and microstructure were also studied. The results show that with temperature increasing, the deposition rate and crystalline size of ZrC coating correspondingly increase. The apparent activated energy is 71.69 kJ/mol, and chemical kinetics is the controlling mechanism at I 473-1 673 K. However, the apparent activated energy changes to 14.28 kJ/mol and the process is controlled by diffusion at 1 673-1 873 K. From 1 473 to 1 673 K, ZrC coating is porous and roughness, crystalline preferred orientations change from (220) to <200>, and microstructure of ZrC coating is typical needle-like. When temperature rises up to 1 873 K, crystalline shows short-column, coating is compact as well as smooth, and deposition rate is highest.