Quartz glass is considered as model ceramic material for selective laser melting (SLM). Single beads of fused powder bonded with a continuous substrate of the same material are obtained. Neither the beads nor the substrates near them are cracked. Low closed porosity in the beads and detachment of the bead borders from the substrate are observed. The quality of the obtained beads is estimated to be sufficient for fabrication of three-dimensional parts by SLM. Comparison with calculations of heat transfer and evaporation reveals that the mass and the energy losses by evaporation are considerable and that the substrate surface should be locally heated up to 1600 K for strong bonding with the bead. Decreasing the thickness of the deposited powder layer is proposed to improve the adhesion between the bead and the substrate with the minimum loss in the productivity of the process. Finer powder is expected to decrease the residual closed porosity in the bead and to make the pores finer too.
Selective laser melting (SLM) of metal powders is being developed starting by the beginning of 2000-ths. The SLM appears to be an effective technology for fabrication of complex-shape functional parts by layer-by-layer building [1-3]. Application of this technique to ductile materials such as austenitic steels, results in high strength immediately due to formation of uniform fine microstructure. Modification of the microstructure and mechanical properties by a subsequent thermal treatment is not excluded. The SLM of brittle materials often results in cracking of the part during the building process. Thus, the authors don’t know a successful attempt to form by SLM a part of a ceramic material with the mechanical strength comparable with that of conventional ceramics. Nevertheless, SLM of ceramic materials continues to attract researchers.
The substrates are plates of quartz glass TU-21-RSFSR-644-83 with non-polished surface of thickness 5 mm produced by Gus F.E. Dzerzhinsky glass factory. The plates are thermally stable up to 600 oC. The powder T 100-0 is produced by Saint-Gobain Quartz with the purity not less 99.96% of amorphous SiO2. The powder contains 90% particles of the size less than 100 mm. Laser sources operating in continuous mode at 10.6 m wavelength where quartz glass is well-absorbing, use sealed CO2 laser tubes of 30 and 40 W output power. The sources are integrated into commercial machines for laser engraving Cencorp 700 LM and Qualitech 203.
After laser scanning, the samples of the beads on the substrate are observed from the top just after the laser treatment as well as after non-treated powder removal with water. The adhesion between the bead and the substrate is judged by eye by light scattering at the interface. The most perspective samples are selected, they are cut, and the polished cross-sections are observed with an optical microscope.