Selective Laser Sintering and Subsequent Gas Nitrocarburizing of Low Carbon Steel Powder
Takayuki Nakamoto*, Nobuhiko Shirakawa*, Yoshio Miyata*, Takumi Sone*, and Haruyuki Inui**
*Technology Research Institute of Osaka Prefecture
2-7-1 Ayumino, Izumi-shi, Osaka 594-1157, Japan
**Department of Materials Science and Engineering, Kyoto University
Sakyo-ku, Kyoto 606-8501, Japan
Optimum conditions for laser irradiation to achieve fully dense SLS (Selective Laser Sintering) specimens have been investigated for S15C steel, in order to check the industrial feasibility of the SLS process. The mechanical properties of SLS processed S15C steel as well as the surface hardenability have also been investigated. The volume fraction of pores in S15C steel decreases as the scan speed, scan spacing and layer thickness decrease and as the laser power increases, so that the density of SLS specimens increases as the energy density increases. The specimens sintered at an energy density of 800 J/mm3 exhibit very low porosity and, hence, very high density, comparable to those of the corresponding wrought material. Complete elimination of pores is indispensable for the ductility and strength of SLS specimens. Excellent wear resistance can be provided with the surface of S15C steel produced by the SLS process by gas nitrocarburizing because of the formation of Fe2-3N nitride with a very high value of microhardness on the surface.