• Piili, Heidi
• Lehti, Antti
• Qian, Bin
• Taimisto, Lauri
• Nyrhilä, Olli
• Shen, Zhijian
• Salminen, Antti

Abstract

Nowadays the widening 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 use of alumina (Al2O3) as a raw material in these cases has raising interest among different industries, since has very favorable properties like high hardness and high melting point. 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 3-D structure of work piece 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 work piece, 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 are actually 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 3-D 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 previously mentioned. The obtained results were collected to be for afterwards analyzed. The microstructure of laser sintered alumina ceramics was characterized both by optical microscope and scanning electron microscope. Results indicate that as laser assisted additive manufacturing is a sensitive process; also change of the process parameters has strong effect to monitoring results. This could also be noticed from micrographs taken from sintered parts of alumina.Nowadays the widening 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 use of alumina (Al2O3) as a raw material in these cases has raising interest among different industries, since has very favorable properties like high hardness and high melting point. 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 3-D structure of work piece 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 work piece, such that in final construction alumina particles are very close to each others. This is followed with post-heatin...

Topics

• impedance spectroscopy
• microstructure
• melt
• hardness
• ceramic
• joining
• sintering
• laser sintering