Densifying method in additive manufacturing process of H13 tool steel : laser re-melting

Abstract

AISI H13 tool steel structures were fabricated by selective laser melting which is one of the metal additive manufacturing process. Scanning speed of laser was controlled in the ranging of 100-1000 mm/s to optimize the process parameter to fabricate the highly densified structure. Laser power, hatch space and layer thickness were fixed at 90 W, 80 μm and 25 μm. Under 200 mm/s, spherical shape pores were observed and irregular shape pores were observed in over 400 mm/s samples. Residual pores were not easily removed by changing laser scanning speed alone and laser re-melting technique was applied to solve the pore problem. Each layers were exposed twice to laser with various scanning speed before re-coating the powder for next layer. Spherical shape pores were observed from all of the specimen exposed under 200 mm/s irrespective of another exposed laser speed. While re-melting over scanning speed of 800 mm/s did not showed 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.