Development of a powder-feed device and procedures for the application of an experimental alloy in overhead PTA-P welding

Abstract

When they are damaged by cavitation, hydroelectric power plant turbine blades must be repaired using operations that could benefit from developments in welding technologies. In light of this, the LABSOLDA welding laboratory at the Federal University of Santa Catarina is making efforts to enhance the flexibility and robustness of the powder-fed plasma transferred arc (PTA-P) process so that it can be used in any welding position and with different powders. The use of consumables in powder form in PTA-P welding allows experiments to be carried out to develop an alloy with special properties suitable for use in generator repairs. To this end, the RV-F PF powder feeder, which can operate with consumables with non-standard morphologies and particle sizes, was developed. The feeder was required to provide a regular flow of consumable material in out-of-position welding operations without the need for high gas flow rates and regardless of the morphology or particle size of the consumables. The RV-F PF is shown to operate efficiently with materials whose properties differ greatly from those of standard consumables. It is also suitable for overhead PTA-P welding and provides a constant supply of filler material efficiently with normal gas flow rates. The welding tests carried out involved deposition of a mixture of two alloys and were followed by cavitation testing of the resulting coating.