MEASUREMENT OF PARTICLE-SIZE OF ULTRAFINE (SUBMICROMETER) WC POWDERS

There is an increasing need for size measurement of particles of submicrometer diameter in the hard-metal and ceramic industries, and in associated technologies such as wear evaluation by wear debris sizing. Specific studies of the problem have been made on fine grained WC powders by comparing the results from conventional instrumental techniques with those obtained by two new methods. The advantages and disadvantages of the various techniques are discussed including the Fisher subsieve sizer, Coulter counter, gas adsorption (BET), laser, sedimentation, and new experimental methods which are based on image analysis and oxidation of WC powders. The most informative and accurate results are those obtained from semi-automatic image analysis of scanning electron micrographs and from comparing the micrographs with a set of computer generated assemblies of similar sized circles randomly positioned wih a frame.