Solidification of PTA aluminide coatings

Components can be protected with coatings tailored using plasma transferred arc to meet specific demands as mixtures of powders with an almost unlimited chemical composition can be processed. In this study, Ni, Fe and Nb aluminide coatings were processed from mixtures of elemental powders on steel substrates and on a Cu refrigerated mold for comparison purposes. Coatings and mini-billets were characterized by means of microhardness, X-ray diffraction and laser confocal microscopy. Examination of the solidification structures showed that for each alloy system coatings are influenced by the exothermal synthesis of the aluminides and the interaction of the plasma arc with the substrate and with the feedstock. The poor flowability of the Ni - Al powder mixture determined its interaction with the plasma arc and strongly affected the dilution of coatings.