Corrosion and strength degradation behaviors of binderless WC material and WC-Co hardmetal in alkaline solution: A comparative investigation

Unsatisfactory corrosion resistance is the main weakness of WC-Co hardmetals and hence, binderless WC materials (bWCs) are considered as the promising alternatives in such tough service conditions. Nevertheless, the knowledge of the quantitative difference in the corrosion resistance and corrosion-induced strength degradation of the two materials are limited. Well-densified straight bWC and WC-10Co hardmetal were fabricated by spark plasma sintering and sinter-HIP, respectively. Corrosion investigations conducted by weight loss, solution analysis and assisted by scanning electron microscopy, X-ray photoelectron spectroscopy, as well as X-ray diffractometer consistently indicate that bWC exhibits excellent corrosion resistance in 1 M NaOH solution. The average corrosion rate (0.045 mm/y) of WC-10Co evaluated by weight loss in the duration of 28 days is approximately 6.4 times that of bWC. Substantial strength degradation and narrowing in the strength gap between the two materials, i.e., from 4.4 times in their original state to 2 times after being continuously immersed for 28 days are observed. The related corrosion behaviors are discussed.