Effects of laser parameters on the fabrication of alumina bodies with boron carbide addition

Reference	Presenter	Authors (Institution)	Abstract
01-026	Rongzhen Liu	Liu, R.(Huazhong University of Science and Technology);	Direct laser sintering is a potential technology to fabricate ceramics without any post treatment. However, due to the tremendous thermal stress during laser sintering, cracks, pores and other drawbacks remain challlenging for direct laser sintering of ceramics. In this paper, alumina was fabricated by direct selective laser sintering under room temperature. 5wt.% Boron Carbide powder (its mean particle size is about 20????m)was added into alumina powder to improve its sintering behavior. The effect of laser parameters was investigated in this study. The particle size of alumina powder was about 45????m. The selective laser sintereing machine used in this study is model HKC250 with a 10.6????m CO2 laser. The whole sintering process was performed under air condition using different laser parametres(laser power:20W, 30W, 40W and scanning speed :150mm/s, 300mm/s, 500mm/s). The layer thickness and scaning space was 0.13mm and 0.1mm respectively. The dimension of sintered square is 10mm*10mm. After laser sintering, the phase transformation was determined by XRD. The elemental ratio of selected area was analysed by EDS. The morphology of sintered alumina was characterised by SEM and porosity data was obtained by Archimede method. The results showed that with the increasing of laser power, the depth of melting pool was increased and the surface accuracy deteriorated. Only tiny cracks was observed in the sintered body. This phenomenon was probably caused by the inhabitation effect of Boron Carbide. However many pore were still remained in the sinterd body which was probably due to the oxidation of Boron Carbide after laser sintering. With the laser scaning speed increased from 150mm/s to 500mm/s, the microstructure caused by laser sintering was more and more finer ?and the inner pores caused by the addition of Boron Carbide showed more and more regular pattern which indicated that the laser scanning speed could affect the distribution of pores.
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