Microstructure Controlling and Properties of ZrO2Coating by Chemical Vapor Deposition
|School||Central South University|
|Keywords||chemical vapor deposition zirconia coating carbon/carbon composites|
C/C composite has many excellent properties and it is a kind of ideal material for aircraft and spacecrafts, but it cannot meet the requirements of some key components of aircrafts because of the rapid development in aircrafts with heavier load, larger force, higher combusting temperature and further distance.Zirconia coatings were prepared by atmospheric pressure chemical vapor deposition(APCVD) from ZrCl4-CO2-H2-Ar system on different conditions in this paper; the thermodynamics of the system were calculated and the Dynamics of the system were analysed; the effects of preparation parameters(such as deposition temperature, Hydrogen flow, deposition position and different substrate) on deposition rate, deposition uniformity, microstructure and micro mechanical properties of zirconia coatings were studied; Ablation resistance of zirconia coatings and multi-coatings with zirconia were investigated and the ablation mechanism of zirconia coatings was concluded. The main conclusions are as follows:(1)The lowest temperature for the deposition of zirconia coatings in ZrCl4-CO2-H2-Ar system is816℃in terms of thermodynamics calculation,as the temperature increasing, the value of equilibrium constant increased so zirconia coatings deposited more easily.(2)Considering deposition rate and microstructure together, the best deposition parameters for zirconia coatings are1300℃,400ml/min Hydrogen flow and Continuous deposition.(3)The zirconia coatings combine better with C/C-SiC substrate than it with C/C-ZrC substrate and the surface scratch of ZrO2coatings on C/C-SiC substrate is smooth while it is rough on C/C-ZrC substrate.(4) The zirconia coatings have some protective effect as thermal barrier coating but it can hardly combined with the substrate so it spalled as it was heated.