Development of Ultra-fine particle Depositon Method to Overlay Coating

本研究提出发展超细粒子沉积法(UDM)作为结构材料涂层的新技术。UDM是作为一种处理超细颗粒的技术提出的。UDM有两个物理阶段：气体蒸发阶段和真空沉积阶段。在气体蒸发过程中，源物质在惰性气体中蒸发形成超细颗粒，利用蒸发室和沉淀室之间的压差释放的气流将超细颗粒与惰性气体一起携带在载气管道中。在沉积阶段，通过喷嘴与载体管端的连接，在沉积室中随气流沉积颗粒，认为沉积超细颗粒的载流速度是薄膜形成的控制因素。提高气流速度是提高超细颗粒载流速度的有效途径。在此基础上，根据喷嘴内一维等熵流动的假设，设计了超音速射流加速的超音速喷嘴，并在喷嘴出口马赫数为3.6的条件下设计了超音速喷嘴。研究结果表明：(1)制备钛、铝金属薄膜需要去除二次团聚形成的粗大颗粒。(2)薄膜的生长速度受蒸发源金属的电功率控制。(3)加热喷嘴能有效地形成无气孔的膜层。(4)微维氏硬度计的金刚石压头在基材与涂层的界面处未产生裂纹，说明两者之间存在较强的结合力。根据本研究的结果，该方法的名称由超细颗粒沉淀法更名为超音速自由射流PVD法。

This study proposed the development of Ultra-fine Particle Deposition Method (UDM) as new coating technology for structural materials. UDM is proposed as a technique for handling ultra-fine particles. There are two physical stages in UDM : gas evaporation and vacuum deposition. During gas evaporation, the source material is evaporated to form ultra-fine particles in an inert gas ; ultra-fine particles are carried with the inert gas in carrier pipe by using gas flow issuing from pressure difference between evaporation chamber and the deposition chamber. In the deposition stage, the particles are deposited with the gas flow by nozzle joined the carrier pipe tip on the substrate in deposition chamber.We considered that carrier speed of ultra-fine particles deposited as controlling factor of film formation in this method. It is effective that gas flow velocity is accelerated in order to accelerate carrier speed of ultra-fine particles. Then supersonic nozzle in which gas flow velocity was supersonic jet accelerated was designed by assumption of one-dimensional isentropic flow in nozzle, and it was designed in Mach 3.6 in the nozzle exit.This study aims to form the metal films of pure titanium and aluminum by UDM using supersonic nozzle. The results obtained are as follows : (1) Removal of coarse particles formed by secondary agglomeration is necessary for producing metallic films of titanium and aluminum. (2) Growth rate of film is controlled by electric power to evaporate source metal. (3) Heating nozzle is effective for the formation of film without voids. (4) No cracks were formed by indenting the diamond indenter of micro Vickers hardness tester at the interface between substrate and coated film, which indicates strong adhesion between them. By the result of this study, the name of this method was changed from the Ultra-fine Particle Deposition Method to Supersonic Free-Jet PVD Method.