Low and high temperature hardness of WC-6 wt%Co alloys

Abstract

The paper reports hardness measurements on WC-6 wt%Co of three different grain sizes in the temperature range from -196 to 900 degrees C. Coarser grades have been found to soften with increasing temperature at a higher rate than finer grades. It has been confirmed that hardness decreases with increasing grain size over the whole range of temperatures and it has been shown that the decrease in hardness with increasing grain size follows a Hall-Fetch-type relationship at all the temperatures tested. For the investigation, disks of 14mm in diameter and 3mm in thickness were used as samples. The grain size was measured by means of a Leica Q500MC image analyser. However this investigation confirmed that the hardness of WC-6 wt%Co decreases with increasing temperature and that the rate of softening is high between 196 and 20°C, decreases between 20 and 600°C, and increases again above 600°C. In addition, this work has shown that the rate of softening is higher for coarser than for finer grades in the range of temperatures investigated.