G. Matthäus, Thermico GmbH & Co KG, Castrop-Rauxel, Germany; K. Bobzin, E. Lugscheider, Surface Engineering Institute (IOT), RWTH Aachen University, Aachen, Germany; J. Zwick, Surface Engineering Institute, RWTH Aachen University, Aachen, Germany
Spraying of oxides with a reduced particle size distribution can lead to very beneficial coating properties concerning density and ductility or crack behaviour. In this work Al2O3 and Cr2O3 powders with a particle size of 250 nm (D50) have been sprayed by atmospheric plasma spraying. A spray equipment with axial powder injection was used to prevent difficulties with the injection of particles into the plasma plume due to their low mass and therefore momentum at typical feed gas flow rates. The powder feed equipment was modified to realise a stable and constant feed rate. The coatings microstructure, porosity and microhardness were studied and compared to coatings based on feedstock powders with a conventional particle size distribution. The crack propagation at microhardness indentations revealed differences in coating ductility between the ultrafine and conventional powder grades.
Summary: Al2O3 and Cr2O3 powders with a particle size of 250 nm have been sprayed by atmospheric plasma spraying. A spray equipment with axial powder injection was used to prevent difficulties with the injection of particles into the plasma plume. The coatings microstructure, porosity and microhardness were studied.
