Direct laser sintering of iron-graphite powder mixture

In the present work, the role of graphite addition on the laser sintering of iron powder was studied. Powder mixtures containing iron and 0.4, 0.8. 1.2, and 1.6 wt.% graphite were prepared by blending elemental powders. These powders were sintered layer-by-layer under nitrogen atmosphere using a continuous wave CO, laser beam. A laser power of 70-225 W, scan rate of 50-600 mm s(-1), scan line spacing of 0.1-0.3 mm, and layer thickness of 0.1 mm was used. It was found that the processing parameters play a key role on the densification of the iron-graphite powder mixtures. The addition of graphite enhances the densification of the iron powder and improves the surface quality of the laser sintered parts when optimized manufacturing conditions are applied. The graphite content has a significant influence on the internal pore structure of the sintered parts. They are gradually changed from interconnected networks to closed and spherical shaped pores with increasing graphite content. The metal matrix structure consists of different phases such as ferrite, austenite, and tempered martensite, which highlights the heterogeneous distribution of dissolved carbon in the iron matrix. This article presents the experimental details of the microstructural evolution in laser sintered iron-graphite powder mixtures. The role and key importance of graphite addition to iron powder in the laser sintering process is addressed. (C) 2004 Elsevier B.V. All rights reserved.