Dr. Yong-Jin Kim, Principal Researcher, Korea Institute of Materials Science, Korea

Title: Microstructure Evaluation with Processing Parameters of Tool Steels Processed by Additive Manufacturing

Abstract: Selective laser melting is one of the important additive manufacturing process because of its capability to make the complex metal parts. H13 steel is one of the difficult metal materials to fabricate the industrial parts due to its high hardness. The selective laser melting process can be efficiently applied to solve this problem. In this study, the effects of processing parameters of selective laser melting on the microstructure and mechanical properties of AISI H13 were investigated and also compare the properties with the conventional H13 steel. Scanning speed of laser was controlled in the ranging of 100-1000 mm/s and laser power, hatch space and layer thickness were fixed at 90 W, 80 μm and 25 μm respectively. Relative density and thermal conductivity of additively manufactured H13 decreased significantly when laser speed over the 1000 mm/s. Additionally, we also studied the effect of the laser re-melting process by introducing multiple laser exposure times on same powder layer. Firstly, we researched about effect of scanning speed of 2 times laser re-melting process. Spherical shape pores were observed from all of the specimen when exposed under 200 mm/s. While the specimens re-melted over scanning speed of 800 mm/s did not showed the increasing effect on the densification, the combination of first scanning speed (400 mm/s) and second scanning speed (600 mm/s) showed the significant reduction of pores. Secondly, re-melting process of triple and quintuple were also studied and the result shows that the sample of the triple exposure times has the lowest amount of pores and highest hardness. Our characteristic study can be usefully applied for the development of H13 component via selective laser melting process.

Keywords: Metal 3D printing, selective laser melting, powder bed fusion, tool steel, laser re-melting