A new viewpoint on the influence mechanism of TaC additions on performance of WC-Co cemented carbides

Abstract

One of the possible ways to improve performance properties of WC-Co cemented carbides for different applications is known to be adding insignificant amounts of tantalum carbide. Performance of mining tools is noticeably improved as a result of small additions of TaC, so that some companies produce WC-TaC-Co grades for mining applications. Despite clear experimental evidence of the positive influence of small TaC additions on the properties and performance of WC-Co cemented carbides, the mechanism of this influence is presently not understood. In the present work a new viewpoint of the influence mechanism of small TaC additions of performance of WC-Co cemented carbides was elaborated. It was established that small amounts of TaC added to WC-Co cemented carbides form an oversaturated solid solution of tantalum in cobalt when solidifying the liquid binder during cooling from sintering temperatures. This solid solution decomposes when further cooling in the solid state resulting in the formation of (Ta,W)C nanoplatelets and rounded nanoparticles embedded in the binder matrix. The effectiveness of cemented carbide with such a nanograin reinforced binder is assumed to be similar to that of the well-known cemented carbides with the binder reinforced by hard metastable W-Co-C nanoparticles implemented in industry about 20 years ago. The production of the cemented carbides with the (Ta,W)C nanograin reinforce binder is more economical and consistent, which ensures the more sustainable manufacture, and the nanoprecipitates are stable at elevated temperatures.