An Evaluation of the Microstructure and Hardness of Co-Rich PTA Overlays on a Duplex Steel Substrate

Overlaying welding is a technology that allows for the acquisition of structural materials with advantageous and complex operating properties. The substrate material can be a material with advantageous mechanical and plastic properties, and the coating can provide corrosion or abrasion (wear) resistance. Among coating application techniques, plasma transfer arc (PTA) overlay welding can be used, where the overlay ensures metallic continuity and high durability, but is a limitation in the joining technologies. Therefore, research was carried out on the possibility of making Co-rich PTA overlay welding coatings on duplex steel, which combine the unique properties of duplex steel and the abrasion resistance of the coating. The tests performed showed that it is possible to apply a coating on the edges of elements without unfavorable changes in the material associated with the formation of carbides and the sigma phase in the HAZ. The coating has a structure of a Co-rich solid solution and a net of eutectics with carbide precipitations. This allowed for high hardness (600 HV10) without the need for additional heat treatment procedures.