Microstructure and properties of spark plasma sintered WC-6Co cemented carbides

摘要

Cemented carbides constitute the main group of tool materials due to their good cutting and strength properties. To produce cemented carbides powder metallurgy methods are used, among which spark plasma sintering is considered to be highly prospective. The paper presents the results of research on the effect of compaction pressure and heating rate on the microstructure and consequently on the density, hardness and fracture toughness of WC-6C0 cemented carbides produced by spark plasma sintering. Sintering using an HP D 25-3 furnace was performed in vacuum at 1200°C for 10 min at a compaction pressure of 50 or 60 MPa and at a heating rate of 200 or 400°C/min. Samples for measurements and testing were cut by electrical discharge machining from the sintered compacts. Density measurements were carried out using the Archimedes method according to ISO 3369:2006 standard, while Vickers hardness measurements were performed according to ISO 6507-1:2007 standard. The fracture toughness was determined. Microstructure observations in backscattered electrons contrast were conducted using a scanning electron microscope. It was shown that the relative density increases with increasing compaction pressure and heating rate, whereby the heating rate is less important. In addition, an increase in hardness affects a reduction in the fracture toughness. The compacts sintered at the compaction pressure of 50 MPa at the heating rate of 400°C/min exhibited the highest hardness of 1726 HV_(30). The fracture toughness of these materials is 8.66 MPa-m~(1/2).