Product Code: ICA11_403

Effect of Process Parameters to Monitoring of Laser Assisted Additive Manufacturing of Alumina Ceramics
Authors:
Lauri Taimisto, Lappeenranta University of Technology; Lappeenranta Finland
Antti Lehti, Lappeenranta University of Technology; Lappeenranta
Heidi Piili, Lappeenranta University of Technology; Lappeenranta Finland
Bin Qian, University of Stockholm; Stockholm Sweden
Olli Nyrhilä, EOS Finland; Turku Finland
Zhijian Shen, University of Stockholm; Stockholm Sweden
Antti Salminen, Lappeenranta University of Technology, Machine Technology Centre Turku Ltd.; Lappeenranta Finland
Presented at ICALEO 2011

Nowadays the increasing range of materials suitable for laser assisted additive manufacturing (laser sintering and laser direct melting) and high automation level of equipments has made this method more interesting process for rapid manufacturing. Also using alumina (Al2O3) as a raw material in these cases is raising interest among different industries since it has high melting point and is very hard material. Alumina is used industrially for example as abrasive, filler, isolator, catalyst and catalyst support.

Laser assisted additive manufacturing of alumina has been very difficult according to literature. There exist a lot of methods to build-up 3D structure of workpiece with the assist of laser beam. In those cases, typically a binder is mixed to alumina and laser melts/evaporates this binder which is joining the particles together thus giving the shape to workpiece, such that in final construction alumina particles are very close to each others. This is followed with post-heating during which the closely packed alumina particles can then be sintered/melted together. There are only a few articles of direct laser beam sintering of alumina. In this case laser beam directly melts material and a 3D structure is formed from alumina powder layer-by-layer as solidified layers of material build on top of each others.

The aim of this study was to examine effect of heat profiles by changing laser power and scanning speed to monitoring of additive manufacturing with direct laser melting /sintering of alumina ceramics. The monitoring was done by using spectrometer, pyrometer and video camera system with active illumination. All tests in this study were carried out with a commercial laser sintering facility EOS M270 installed at Stockholm University (Sweden) consisting of IPG 200W fiber laser and inert atmosphere. The pure alumina powder was used as precursor material.

Process was examined with fixed monitoring devices of spectrometer, pyrometer and video imaging and the obtained results were collected for afterwards analyzes. The microstructure of laser sintered alumina ceramics were characterized both by optical microscope and scanning electron microscope. Results indicate that as laser assisted additive manufacturing is sensitive process, also changing the process parameters has strong effect to monitoring results. This could also be noticed from micrographs taken from sintered parts of alumina.