Additive manufacturing of alumina parts by indirect selective laser sintering and post processing

Innovative powder preparation and post-processing techniques can be employed to obtain high density ceramic parts by means of indirect selective laser sintering. Thermally induced phase separation (TIPS) was used to produce polymer and polymer-ceramic composite particles. The effect of polymer concentration, cooling rate, stirring and alumina particles on polymer and polymer-ceramic composite particles was investigated. Homogeneous spherical alumina-polypropylene (PP) composite powder was synthesized by TIPS for selective laser sintering (SLS). Green Al2O3-PP component parts with a density of 34% could be produced by conventional SLS of the polymer under optimized laser power, scan speed, scan spacing and powder preheating temperature. Various post-processing techniques like pressure infiltration (PI), warm isostatic pressing (WIPing) or a combination of both were applied to increase the green density of the Al2O3-PP SLM parts. Infiltrating the open porosity green SLS parts with a 30 vol% alumina-powder based ethanol suspension allowed to increase the sintered density, i.e. after polymer debinding and pressureless sintering in air at 1600 C, from 38 to 64% of the theoretical density (TD). WIPing of the SLS and SLS/infiltrated green parts at 135 C and 64 MPa allowed raising the green density up to 93 and 83% TD and a sintered density up to 89 and 88% TD, respectively. (C) 2013 Elsevier B.V. All rights reserved.