Effect of metallurgical defect and phase transition on geometric accuracy and wear resistance of iron-based parts fabricated by selective laser melting

A systematic analysis of effect of metallurgical defect and phase transition on geometric accuracy and wear resistance of iron-based parts fabricated by selective laser melting was conducted. By composition optimization of alloying elements, the desirable martensitic structure was directly obtained based on high-speed laser induction and the content of retained austenite was observed to be different under various laser parameters. Using an optimized scan speed of 1600 mm/s could lead to the highest densification level of 99.24% and the lowest content of retained austenite of 3.5%, hence acquiring a considerably high Rockwell hardness of 61.9 HRC, a reduced coefficient of friction of 0.40, and wear rate of 1.8 x 10(-5) mm(3)/N m. A thorough investigation of dimension offset due to martensite transformation in conjunction with theoretical calculation was performed. Lower top surface roughness (5.25 mu m) and reduced side roughness (13.84 mu m) were achieved at the optimized scan speed of 1600 mm/s.