Study On Preparation Process Of Yttrium Oxide Coatings By Metalorganic Chemical Vapor Deposition

Yttrium oxide exhibits great stability at high temperatures, and has good property of reducing permeation of tritium and good electric insulation property. Because coatings can be formed on materials of complicated shape by using the method of metal organic chemical vapor deposition, the method of metal organic chemical vapor deposition has broad application prospects,316L austenic steel is the earliest adopted candidate structural material for fusion reactors. The processing properties of the material are good. The preparation process and the usage process are experienced. CLAM steel is one of RAFM (Reduced Activation Ferritic/Martensitic) steels. CLAM steel has great resistance to irradiation swelling and good thermal physical properties.In this paper, we prepared yttrium oxide coatings by using the method of metal organic chemical vapor deposition. The former two materials were selected as substrates:316L austenitic stainless steel and CLAM (China Low Activation Martensitic Steel). Yttrium oxide thin coatings exhibit good crystallization by choosing a proper technological parameter. The influence of deposition temperature and deposition pressure to properties of the coatings such as surface topography, phase structure, binding force and residual stress etc was investigated here. The insulating resistivity of the coating was tested, which reached the value of 5.12×1011Ω·m. The effect of annealing process to the uniformity of the coatings was studied. Therefore, the preferable preparation parameters and annealing process were achieved.The deposition temperature and the deposition pressure have great impact on the surface topography of the coatings and other properties of the coatings. For coatings deposited on the 316L steel substrate, the preferable parameters were at the temperature of 600 DEG C and under the pressure of 1000Pa. Coatings deposited under the preferable parameter were uniform and dense, have strong bond with the substrate and have good electric insulation property, which can meet the insulation requirement of TPB coatings. The residual stress of the coatings was small. The thickness of the coatings was 2.5 microns to 3 microns. The deposited coatings were polycrystalline. The improvement of the surface topography of the coatings annealed at different atmospheres was investigated. The uniformity of the coating annealed at argon atmosphere was better compared with that of the coating annealed at oxygen atmosphere.For coatings deposited on the CLAM substrate, the preferable parameters were at the temperature of 600 DEG C and under the pressure of 1000Pa. Coatings deposited under the preferable parameter were uniform and dense, and exhibited good crystallization. The thickness of the coatings deposited under the pressure of 500 to 1000 Pa was 1.5 microns to 3.5 microns. The binding force between the CLAM substrates and the coatings was very small. The improvement of the surface topography of the coatings annealed at argon atmosphere and oxygen atmosphere was investigated. The uniformity of the coating annealed at argon atmosphere was better.