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Tuesday, May 16, 2006
EP17.1

Effects of Deposit Surface Temperature on Mechanical Properties of Fe-C Arc-sprayed Tools

K. H. Baik, Chungnam National University, Daejeon, South Korea; J. H. Kim, B. G. Seong, RIST, Pohang, South Korea

Spray tooling employing electric arc spraying onto a ceramic master pattern is being an emerging cost effective technology to manufacture a thick carbon steel shell for near net shape of dies or moulds. In order to minimize residual stresses in a large sized shell, the deposit surface temperature should be controlled by spraying conditions, mainly arc current, and this influenced deposit microstructure and mechanical properties. Each Fe-C steel shells have been manufactured at a constant deposit surface temperature from 250oC to 450oC. A higher deposit surface temperature required for spraying at a higher arc current, i.e. a higher wire feedrate, which promoted a lower fraction of oxide and a higher residual carbon content in the sprayed shell. An increase in deposit surface temperature led to a slight decrease in deposit hardness, because of phase transformation from martensite to bainite. The tensile strength and the bend strength of sprayed shell increased gradually with increasing the deposit surface temperature, and the increase in bend strength was much pronounced. Fractographic studies showed that the tensile and bend strengthening was mainly attributed to an increase in adhesion between splats as well as the reduced oxide fraction. 

Summary: In order to minimize residual stresses in a large sized sprayed shell, the deposit surface temperature should be controlled by spraying conditions, mainly arc current. This study describes the deposit microstructure and mechanical properties of Fe-C arc-sprayed shell as a function of deposit surface temperatures.