Sliding wear performance of Fe-, Ni- and Co-based hardfacing alloys for PTA cladding

Stellite 6, Colmonoy 56, and SKS3 tool steel are typically the materials used as weld hardfacing claddings or as-cast to provide the needed wear resistance to a base material with the required mechanical properties. In this study, a series of Co- and Ni-based hardfacing alloys are successfully fabricated on a substrate of S45C carbon steel using the plasma transferred arc process with Stellite 6 and Colmonoy 56 powders. An Fe-based hardfacing alloy is used on commercial SKS3 tool steel for comparison. The microstructure, hardness and wear resistance of the three materials are investigated systematically. The two claddings and the as-cast SKS3 examined belong to the categories of Co-, Ni- and Fe-based hardfacing, respectively, with hard carbides/borides in their microstructures. The two different claddings are not only tested against SKS3 tool steel but also against each other using the ring-on-disk wear test. After the wear test, the worn surfaces are examined using scanning electron microscopy and energy dispersive spectroscopy to identify the dominant wear mechanisms. The experimental results show adhesive wear is confirmed by metal transfer from a hard surface to a softer one in Stellite 6 against SKS3, and in Colmonoy 56 against the Stellite 6 specimens, while surface deformation testifies to abrasive wear. The transfer layer formed on the surface prevents direct metal-to-metal contact and reduces the wear loss. For Colmonoy 56 against SKS3, adhesion does not occur; instead, Colmonoy 56 causes serious abrasion on SKS3 due to its greater degree of hardness and causes significant wear loss for SKS3.