抄録
Physical and mechanical characteristics of brass coating sprayed with an electrically operated pistol under various conditions were studied. The arc-voltage and the pressure of air blast in the spraying were found to have a marked influence on the composition of the coating, that is, the content of Cu in the coating increased with increasing voltage and pressure, in spite of the fact that it is almost independent of the condition of spraying with a gas pistol. The microstructure of the coating was very complicated owing to the presence of oxides, eutectics, etc. The coefficient of thermal expansion of the brass between 20° and 70° was nearly 10% smaller than the normal brass of the same composition. A small irregular contraction at about 340° which is due to the recrystallization was also observed during the heating. The apparent specific gravity was nearly 15% smaller than the real value, while the electric resistance was 2.64-3.78 times larger than the normal brass, indicating that the coating is porous and rich in oxides. The hardness depended markedly upon the pressure of air blast. The tensile strength, elongation and the impact value were quite small, owing to the brittleness of the coating. The adhesive strength of the coating sprayed on the soft steel depended much on the degree of roughness of the steel surface.
