WC Grain Growth and Growth Inhibition in Hardmetals Looking Back to 30 Years of RD at Vienna University of Technology

摘要

After 30 years of experience in research and development on cemented carbides a critical look back is made on the growth of the WC phase in hardmetals.Other than in case of spherical grains which undergo normal Ostwald Ripening,the growth of the WC occurs in a facetted mode,where a significant further growth is possible only when assisted by 2-D nucleation or defects.In this case there is no linear relationship between the growth rate and the supersaturation,as considered in Ostwald ripening,but the growth rate is assumed to abruptly increase at a certain supersaturation.The kinetics of the nucleation and interface growth does play a crucial role and the mechanisms behind can be regarded as the resistance of the system against growth.This resistance is remarkably influenced by defects,but also by the chemical environment of the growing WC crystals (nature of the binder; C-activity; growth inhibitor).