Erosion-corrosion resistance of tungsten carbide hard metals with different binder compositions

摘要

A study has been made of the slurry erosion resistance of a series of cemented tungsten carbides with different binder compositions consisting of combinations of cobalt, nickel and chromium. Testing was carried out on a specially designed laboratory rig in both tap and salt water using silica sand as an erodent. The synergistic action of erosion and corrosion on WC hard metals results in greatly enhanced wear rates compared to either erosion or corrosion processes alone. Cemented carbides with a 1 0 wt% binder were found to have a better slurry erosion resistance than the corresponding 6 wt% binder grades or the pure metal binder alloys alone. The performance of all the materials was found to be much worse in a salt water medium compared to tap water. The alloying of either pure Nickel or Cobalt binders was found to influence the fracture properties and corrosion resistance and lead to an improvement in the slurry erosion resistance of the cemented carbides. However any improvement in the corrosion resistance of the binder did not directly enhance the slurry erosion resistance of the cermet. Explanations are advanced to explain these differences in behaviour linked to chemical composition, mechanical properties of the binder phase and the dynamic nature of the slurry erosion system. Comparisons are also made between the performance of the Ni-Cr-Co based cermets and the pure alloyed metal binder grades. The acceptability of modelling the slurry erosion and corrosion resistance of cermets based on the behaviour of the binder phase materials is discussed.