Corrosion Behavior of the S136 Mold Steel Fabricated by Selective Laser Melting

The selective laser melting (SLM) method has a great potential for fabricating injection mold with complex structure. However, the microstructure and performance of the SLM molds show significantly different from those manufactured by traditional technologies. In this study, the microstructure, hardness and especially corrosion behavior of the samples fabricated by SLM and casting were investigated. The XRD results exhibit that the -Fe phase is only obtained in the SLM parts, and the -Fe peak slightly moves to low diffraction angle compared with casting counterparts. Due to the rapid cooling rate, the SLM samples have fine cellular microstructures while the casting ones have coarse grains with obvious elements segregation. Besides, the SLM samples show anisotropy, hardness of side view and top view are 48.73 and 50.31 HRC respectively, which are 20% higher than that of casting ones. Corrosion results show that the SLM samples have the better anti-corrosion resistance (in a 6% FeCl3 solution for 48h) but the deeper corrosion pits than casting ones. Finally, the performance of the SLM molds could meet the requirement of injecting production. Moreover, the molds especially present a significant decrease (20%) of cooling time and increases of cooling uniformity due to the customized conformal cooling channels.