Synthesis of ultrafine WC-Co composite powders under hydrogen atmosphere with in situ carbon via a one-step reduction-carbonization process

Abstract

An inexpensive and facile direct method to synthesis ultrafine WC-Co composite powders was proposed employing soluble starch as an in situ carbon source in a H2 atmosphere via a one-step reduction-carbonization process. Influences of processing factors, such as temperature, H2 flow rate, and reaction time have been investigated. The results revealed that the system of synthesis process was dynamic in nature where temperature, H2 flow rate, and reaction time had a suitable value to achieve the desired product phase. Mainly due to the gas reaction and homogeneous in situ carbon, the synthesizing temperature and reaction time were greatly lower than the conventional method. Lowering the reaction temperature and increasing the reaction rate would lead to finer WC-Co composite powders. Ultrafine WC-Co composite powders with almost no unwanted phases were obtained under the H2 flow rate of 0.75 m3/h at 950°C for 0.5 hour and the average particle size was 155 nm with good dispersion. Furthermore, the mechanism for the phase transformation was discussed in this study as well.