Microstructure and physical and mechanical properties of micro cemented carbide injection moulded components

Abstract

Micro cemented carbide (WC–Co) injection moulded components were fabricated using a powder injection moulding (PIM) process. At first the WC–Co powder was mixed with a binder system. Powder-binder mixture as called feedstock is then moulded into desired shape and followed by debinding process. After debinding, the samples were sintered at a temperature range between 1370°C and 1450°C for 3min and 8min. The effects of sintering processing parameters on the microstructure and the physical and mechanical properties of the components were investigated. According to field emission scanning electron microscopy (FESEM) observations of the microstructure, tungsten carbide (WC) particles are homogeneously distributed and have excellent bonding with the cobalt (Co) metallic matrix. The sintering cycles at 1410°C with an 8min holding time lead to optimise physical and mechanical properties. This sintering cycle indicated low porosity among the sintered parts. The relative density and hardness of micro WC–Co injection moulded components increased with the increase in sintering temperature and the best relative density obtained was 97.57% of the theoretical density at 1410°C with an 8min holding time. The highest hardness value of 1645HV was obtained at a sintering temperature above 1410°C. However, the highest transverse rupture strength (TRS) of 1120MPa was achieved at 1410°C with an 8min holding time, and the TRS decreases with a further increase in the sintering temperature.