Development of a quantitative method for grain size measurement using EBSD : and Comparison of WC-Co materials produced with different production methods

Abstract: High performance cutting tools are essential in many industry areas. Cemented carbides (WC-Co) are common materials used for these applications due to the excellent mechanical properties. The mechanical properties of the material are manly dependent on the WC grain size distribution.To be able to tailor the material properties it is important to be able to characterize and control the WC grain size.In this study a quantitative method for WC grain size distribution measurements has been developed using the automated electron backscatter diffraction (EBSD) technique. The EBSD system was optimized for a fast and accurate measurement. Using the method approximately 2000-3000 WC grains can be measured in approximately 25 minutes. This will give reliable statistics and information about the material.The method was used to compare materials produced with three different milling methods; traditional 30l ball mill, method A and B. Two WC raw materials with different initial particle sizes, one coarser and one finer, was milled aiming for similar grain sizes in the sintered structure. The results showed some tendency for a larger fraction of large grains in the materials produced using the ball mill compared to the materials produced with method A and B. The difference between the milling methods was larger using a raw material with a coarser initial particle size.The developed quantitative method was successfully used to compare grain size distributions of different materials in a fast and quantitative way. The differences between the materials were small and materials with similar grain size distribution and mechanical properties could be produced using both the traditional ball mill method and method A and B.