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2580579 
Journal Article 
AN INVESTIGATION INTO FULLY MELTING A MARAGING STEEL USING DIRECT METAL LASER SINTERING (DMLS) 
Stanford, M; Kibble, K; Lindop, M; Mynors, D; Durnall, C 
2008 
1 
Steel Research International
ISSN: 1611-3683 
847-852 
WOS:000267944700121 
This paper reports on the relative capability of the EOS M250 Extended platform to fully melt an 18Ni ('300' grade) maraging tool steel from sub-20 mu m powder, The work describes the investigation of scanning routines necessary to achieve satisfactory metallurgical integrity and shape manufacturing capabilities of the process. Solidification was observed to take place by cellular and cellular-dendritic growth mechanisms in DMLS of the maraging steel. Intercellular spacing was less than I pm and this contributed to the excellent strength and hardness achieved for both as-sintered and aged material. Aging at 490 degrees C for 6 h led to an increase in hardness and strength through the precipitation of Ni(3)(Mo,Ti) and Fe(2)Mo intermetallics. Ultimate tensile strength increased from 1101 to 1875 MPa, Vickers hardness increased from 387 to 603 kg/mm(2) but elongation was reduced from 11.3 to 1.8% by aging the steel. These test results were within the tolerance specification for the material. The overall length of the test specimens was measured in the as-sintered and aged conditions. Uniformity was very high before and after the aging treatment, Shrinkage after aging was only 0.061%. The results confirmed that the maraging steel could be successfully manufactured on the M250 Extended platform. 
Laser Sintering; Maraging Steel; Additive Layer Manufacture