Tungsten Carbide Anti-corrosion Research (2/2)

There is an experiment chooses WC-10(CoNi) tungsten carbide as an object of study. In order to test the anti-corrosion, it adds different content of Co in the binder and finds that Cr element effectively increases the anti-corrosion of tungsten carbide and the hardness increases with the increasing content of Cr. Another study is about corrosion behavior with WC-9Ni-0.57Cr carbide simulation in seawater, the study found that in deep-sea high pressure, corrosive environments on corrosion resistance is concerned, compared to conventional WC-Co carbide system to Ni-Cr alloy as the binder phase has better corrosion resistance.

Recently, some foreign scholars have also studied the correlation titanium carbide (TiC), tantalum carbide (TaC) and chromium carbide (Cr3C2) added impact on the corrosion resistance of the alloy. They believe that an appropriate amount of such reinforcement TiC ceramic composite materials can improve toughness of the alloy, and TiC and TaC has excellent chemical stability, only some of the acid is dissolved in, super acid and alkaline oxide solution: While Cr dissolved in the bonding phase accordingly in its surface layer of passive film is formed, it will not change the strength of the premise, significantly reduce the current density, and the higher the ratio of Cr alloy and Co, the passivity of alloy becomes higher. Furthermore, adding aluminum (Al) in the binder is also a new attempt of researchers. Theoretically, Al can be formed of metal bond compound (Co3Al), will make a fundamental change in the binder phase from the structure and performance, the amount can be increased to improve the content of Al alloy high temperature oxidation resistance and corrosion resistance.

The latest research has progressed to the development of adhesive-free alloy, which is free or very little binder metal content, high hardness (up 95HRA above), corrosion and oxidation resistance is also very good, but its flexural strength and fracture toughness is lower, which is difficult for machining. Overall, for the study of the corrosion of cemented carbide mainly includes three aspects, one is to replace the binder phase, and the second is to strengthen the binder phase by adding elements, hard phase grain refinement, the third is the development of adhesive-free tungsten carbide.

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