Development of Ultra-fine particle Depositon Method to Overlay Coating

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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.