Effect of substrate temperature and ambient pressure of deposition chamber on contact condition between free falling droplet and substrate surface were investigated. Cu droplet and SUS304 substrate were used for the experiment. To estimate the contact condition, temperature history of molten droplet was measured at splat-substrate interface by thermocouples embedded in the substrate and high frequency data logging system. Quantitative porosity on splat bottom surface and degree of circularity of splat shape was evaluated. Splat adhesion strength experiment was conducted and dynamic wetting behavior of substrate by molten droplet was captured by ultra-high speed video. Heating substrate and vacuuming chamber pressure enhanced the heat transfer from splat to substrate, which can be attributed to the good contact at splat bottom surface. Adhesion strength of the splat to the substrate corresponded well with degree of circularity. Consequently, substrate temperature and ambient pressure of deposition chamber have an equivalent effect to contact condition at interface between droplet and substrate surface.

Generally, the surface of a substrate is roughened by blasting in pretreatment thermal spraying. Since some of the grit remains on the substrate surface, sprayed coating and the adhesion property characteristics are degraded. However, it seems that there is almost no research on this problem. In this study, residual grit is quantitatively evaluated, and a technique for reducing grit is proposed. For residual grit reduction, a solid lubricant was used, and applied to the surface of a substrate or grit; reduction of residual grit was confirmed. After blasting with solid lubricant, it remained on the substrate surface, which could be removed by heating the substrate.

Usually small samples are used to test corrosion resistance of a coating, it is sometimes difficult to make a coating on the small samples. When a cylindrical sample is used and the coating is formed on whole of the surface, three or four times coating processes are required. Thus an abacus bead type sample is proposed in this paper. In this sample, only two times coating processes are required to make coating on whole of the surface. In this paper, the high-temperature corrosion resistance of a novel coating made of Cr-based alloys for use in waste incineration plants is tested and compared with the coating made of a Ni-based alloy. Paper includes a German-language abstract.