Interaction between WC and Inconel 625 under Solid and Liquid State Sintering Conditions

Abstract

Cobalt is the most used metal binder in hard metals since its extraordinary wetting, adhesion and mechanical properties. Nevertheless, it has been recognized genotoxic and cancerogenic with higher toxicity in combination with WC. To substitute Co with an alternative binder, the interaction between the binder and WC must be taken into account. In this work, IN625 is considered as a binder alternative due to its desirable combination of high-temperature strength and corrosion/oxidation resistance. A characterization of the interaction between WC and IN625 was carried out by means of Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDXS) and X-Ray Diffraction (XRD). Depending on the sintering temperatures, different phases were evidenced at the WC–IN625 superalloy interface. From 1250 °C to 1300 °C, where solid-state sintering takes place, (Cr,Mo)23C6, W2C and (Cr,W) solid solutions were detected. At a sintering temperature of 1350 °C, IN625 melts and the formation of additional phases, such as an intermetallic Ni4W phase and (Mo,W) and (Mo,Nb) solid solutions, were observed. The precipitation of NbC and (Mo,Cr)23C6 carbides in IN625 was also detected.