The deposition behavior of sprayed individual metallic particles on the substrate surface in the cold spray process was fundamentally investigated. As a preliminary experiment, pure copper (Cu) particles were sprayed on mirror-polished stainless steel and aluminum (Al) alloy substrate surfaces. Process parameters that changed systematically were particle diameter, working gas, gas pressure, gas temperature, and substrate temperature, and the effect of these parameters on the flattening or adhesive behavior of an individual particle was precisely investigated. Deposition ratio on the substrate surface was also evaluated using these parameters. From the results obtained, it was quite noticeable that the higher substrate temperature brought about a higher deposition rate of Cu particles, even under the condition where particles were kept at room temperature. This tendency was promoted more effectively using helium instead of air or nitrogen as a working gas. Both higher velocity and temperature of the particles sprayed are the necessary conditions for the higher deposition ratio in the cold spraying. However, instead of particle heating, substrate heating may bring about the equivalent effect for particle deposition.

Application of cold spray process is expected in the various industrial fields such as automobile, aircraft and electronics. So many investigations for practical application have been actively performed in many research organizations. However, as the process has just started in these days, fundamental aspect like deposition mechanism itself has not been well understood up to today. To establish the higher reliability or controllability of the cold spray process, fundamental research, especially on the deposition mechanism, may become a key for the process development. We tried the clarification of particle deposition mechanism in cold spray process by experimental approach. In this study, deposition behavior of sprayed individual particle onto substrate surface was investigated precisely.Self designed cold spray equipment was installed in the laboratory and deposition behavior of sprayed individual metallic particles on the substrate surface was fundamentally investigated. As a preliminary experiment, pure Cu particles were sprayed on mirror polished stainless steel substrate surface. Particles diameter, process gas, gas pressure, gas temperature and substrate temperature were systematically changed as the process parameters, and effect of these parameters on the flattening or deposition behavior of an individual particle was investigated.

The authors develop the space Gas Hollow Tungsten Arc (GHTA) welding which can be performed in a vacuum, since 1993. In order to establish the space welding technologies necessary for the space development, we are also developing the space Diode Laser (DL) welding process in which the welding principle is completely different from the space GHTA welding. The paper describes the welding results by the perpendicular irradiation and oblique irradiation of the laser light in a vacuum. The DL welding experiments using the stainless steel clarified the melting characteristics and the evaporating phenomena in molten metal. And also, it has been clarified that the mass of the metal vapor during welding increases with the reduction of the environmental pressure and the radiation distribution of evaporation metal follows the cosine law.( 426 )

Self designed cold spray equipment was installed in the laboratory and deposition behavior of sprayed individual metallic particles on the substrate surface was fundamentally investigated. As a preliminary experiment, pure Cu particles were sprayed on mirror polished stainless steel and Al alloy substrate surfaces. Process parameters changed systematically were particles diameter, working gas, gas pressure, gas temperature and substrate temperature, and effect of these parameters on the flattening or adhesive behavior of an individual particle was precisely investigated. Deposition ratio on substrate surface was also evaluated on these parameters. From the results obtained, it was quite noticeable that the higher substrate temperature brought about higher deposition rate of Cu particles even under the condition with particles temperature kept at room temperature. This tendency was promoted more effectively by using helium instead of air or nitrogen as a working gas. Both higher velocity and temperature of the particles sprayed are the necessary conditions for the higher deposition ratio in the cold spraying. However, instead of particles heating, substrate heating may bring about the equivalent effect for the deposition of the particles. This finding is quite new and has never been reported.

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