Microstructure and Corrosion Behavior of Re-Added Cemented Carbides in Simulated Seawater

WC-10(Co-xRe) cemented carbides were prepared by vacuum sintering. The addition of Rhenium (Re) resulted in the grain refinement and martensite phase transition of cemented carbides. Additionally, increased grains and phase boundaries were observed in the cemented carbides using SEM and electron back-scattered diffraction (EBSD), leading to increased corrosion sites and corrosion current (I_corr). However, the corrosion voltage (E_corr) of the cemented carbides containing Re increased due to Re’s higher standard electrode potential compared to Cobalt (Co). An excessive amount of Re led to the precipitation of the secondary phase in the cemented carbides, which formed new galvanic batteries between different phases. In the WC-9Co-1Re cemented carbide, a maximum charge transfer resistance of 1183.0 Ω cm² was achieved. The passivation film, composed of Co(OH)₂ and Co₃O₄, isolated the cemented carbide from the corrosive medium, thereby inhibiting further corrosion. Primary corrosion mechanisms involved the dissolution of the Co binder phase and exfoliation of the WC grains. The optimal corrosion resistance was obtained by adding 1 wt pct of Re to the cemented carbide.