Abstract

Plasma transferred arc (PTA) is now currently used for reclamation of worn materials or to provide wear or corrosion resistant coatings welded to the base material. Instead of injecting the powder in the molten pool created at the coated surface, another way to coat substrate surface before the PTA treatment has been studied. As the powder can not be simply deposited on the substrate surface because of the plasma flow which would blow it off before melting it, a tape casting process was used to obtain an adherent powder layer on the material surface. Its cohesion and adhesion to the substrate are due to the organic binder contained in the tape to form organic bridges between particles. In this paper, the electrical properties of NiCu (70/30) tapes deposited on cast iron substrates were first studied. It has been shown that the binder led to a low electrical conductivity of the layer. PTA treatment of the casted tapes has been carried out by starting the electrical arc on the metallic cast iron substrates. The process control by CCD camera allowed to observe that the NiCu particles fell in the melting pool created at the substrate surface. The study of the obtained alloy compositions has shown the drastic influence of the initial binder concentration in the tape. Moreover, before being treated by PTA, some NiCu tapes were heated in a furnace at 1100°C for 4 hours to remove the organic binder and sinter the layer. The coatings thus produced, which were characterized by a low electrical resistivity and a good adhesion to the substrate, were then treated by PTA. The surfacing alloy properties were compared to those obtained without heat treatment.

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