The role of Y2O3, Cu, Mo and Mo2C additives on optimizing the corrosion resistance of WC-6Co cemented carbide in HCl and NaOH solutions

Abstract

WC-6Co cemented carbide is obtained via Spark Plasma Sintering (SPS) using ammonium metatungstate, cobalt acetate and glucose as raw materials. The effects of additive type (Y2O3, Cu, Mo and Mo2C) on the microstructure and anti-corrosion ability of WC-6Co cemented carbide in HCl and NaOH solutions are investigated. The results show that the addition of Y2O3, Cu, Mo and Mo2C additives can enhance the anti-corrosion ability of WC-6Co cemented carbide. Among them, the enhancement effect of Mo is much better than other additives in grain refinement and performance improvement. By analysis, the action process and mechanism of Mo on the corrosion resistance of WC-6Co cemented carbide in different solutions are different. In HCl solution, the formation of MoO3 can adhere to the contact interface to segregate corrosion solution, and then inhibit the conduction of electrons. However, MoO3 is easily transformed into soluble HMoO42− and MoO42− in NaOH solution. Meanwhile, Mo can refine the WC grains to increase the number of WC/Co grain boundaries. In the early stage of corrosion process, the stable Co(OH)2 is prone to form at the grain boundaries and then adheres to the interface to isolate corrosion medium and electron conduction, thereby improving the anti-corrosion ability of WC-6Co cemented carbide.