Additive manufacturing of high performance oxide ceramics via selective laser melting

Oxide ceramics such as Alumina (Al2O3) and Zirconia (ZrO2) are widely utilized in various engineering fields due to their excellent mechanical properties along with outstanding thermal and wear resistance. Their biocompatibility, strength and esthetics also qualify these oxide ceramics for medical applications. Limitations to the geometry and shrinking during the conventional sintering process often prevent utilization of these high-strength ceramics in various applications. These limitations may be overcome by employment of Additive Manufacturing (AM) techniques, allowing for layer-wise generation of complex-shaped components directly from CAD data. The present work studies AM of ceramic specimens, based on Al2O3/ZrO2 powder by means of Selective Laser Melting (SLM). Towards this end, the powder material is qualified in terms of flowing ability and optical characteristics, aiming at developing a new process in which pure ceramics are completely melted by a laser beam, yielding net-shaped specimens of almost 100% densities without any post processing. Formation of cracks is suppressed by high-temperature preheating at which new preheating concepts are developed and compared in terms of thermoanalyses and the resulting property profiles. Employing the eutectic Al2O3/ZrO2 mixture ratio results in a fine-grained microstructures and flexural strengths of up to 1150 MPa. Dominating effects of high-temperature SLM on the surface quality are analyzed and filigree structures of < 300 µm wall thickness and a profile roughness of Rz < 70 µm are achieved. For demonstration purposes fully ceramic dental restorations have been manufactured, highlighting the possibilities of manufacturing individual complex shaped high-strength ceramic components by means of SLM