Development of Ultra-fine particle Depositon Method to Overlay Coating

本研究提出了超细颗粒沉积法（UDM）作为新型结构材料涂层技术的发展方向。UDM是一种处理超细颗粒的技术。UDM有两个物理阶段：气体蒸发和真空沉积。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；利用蒸发室与沉积室压差产生的气流，将超细颗粒随惰性气体一起输送到载体管中。在沉积阶段，颗粒通过与载体管尖端连接的喷嘴在沉积室的基材上随气流沉积。我们认为沉积的超细颗粒的载流子速度是该方法成膜的控制因素。为了加快超细颗粒的载速，加快气体流速是有效的。基于一维等熵流动假设，设计了气体流速为超声速射流加速的超声速喷管，并在喷管出口设计了3.6马赫的速度。本研究的目的是利用超音速喷嘴用UDM形成纯钛和纯铝的金属薄膜。结果表明：(1)去除二次团聚形成的粗颗粒是制备钛铝金属薄膜的必要条件。(2)薄膜的生长速度由电力控制，使源金属蒸发。(3)加热喷嘴对形成无空隙的薄膜有效。(4)用显微维氏硬度计的金刚石压头在基材与涂膜界面处压痕未形成裂纹，表明基材与涂膜之间的附着力较强。根据本研究的结果，将该方法的名称从超细颗粒沉积法改为超音速自由射流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.