Effect of Dry and Wet Ball Milling Process on Critical Powder Loading and Mixture Properties of Fine WC-10Co-0.8VC Powder

Abstract

Micro powder injection molding (μPIM) has great potential for the production of micro cemented carbide parts that require high hardness and toughness. The main stages of the μPIM process include mixing the powder and organic binder, injecting, debinding, and sintering. High critical solid loading of submicron tungsten carbide (WC) powder is one of the requirements in the micro powder injection molding process, which is not obtained easily. This paper investigates the effects of ball milling on critical solid loading of submicron WC. Dry and wet ball milling processes were used to prepare a powder mixture with composition of WC-10Co-0.8VC (wt-%). Critical powder volume concentration (CPVC) was determined using the torque variation method, and the powder characteristics were assessed using scanning electron microscopy and energy dispersive X-ray spectroscopy. CPVC was at 42% and 50% for the dry and wet ball milling processes, respectively. Apparent and tap densities of the powder mixture were achieved at 2.4 g/cm3 and 2.96 g/cm3 after dry milling and at 2.54 g/cm3 and 3.39 g/cm3 after wet milling, respectively. Wet ball milling causes fine particles to de-agglomerate and improves the critical solid loading, which is advantageous for submicron cemented tungsten carbide injection molding. The homogeneity of the powder mixture can improve under longer time of wet milling process and it can be expected that reduce microstructure defects in sintered components.