Effect of Sintering Time on Mechanical and Magnetic Properties of Cemented Carbides

Producing of today cutting tools without cemented carbides as a raw material is impossible. Requirements of industries to new cutting tools with high quality and performance in order to achieving better economical results, was caused to use of advanced processes in producing and improving of these tools. In this research, it is endeavored by changing sintering time, new properties and broadened fields of cemented carbide tools are obtained. For this purpose, samples of “K” type standard with WC(92%Wt), TaC(2%Wt) and Co(6%Wt) composition and “P” type standard withWC(80%Wt), TaC(5%Wt), TiC(5%Wt) and Co(10%Wt) composition which are suitable for cast iron and steel machining respectively, were processed. Microstructure of raw materials and products were investigated by light and scanning electron microscopy respectively. Samples were sintered at 1490±5°C for 1 to 10 hours in a 10-2torr vacuumed electric furnace. Analyzing of XRD patterns by software revealed desirable phases. Mechanical properties were analyzed by measuring of hardness changing from 1698HV30 to 1674HV30 for “K” type and 1389HV30 to 1347HV30 for “P” type samples. Transverse rupture strength of samples was measured after 4hr sintering and an increasing revealed up to 2991MPa for “K” type and 2710MPa for “P” type samples because of elimination of crack formation centers and after that decreased to 2610MPA and 2250MPa because of predominant of grain growth phenomenon, respectively. Also measurements of magnetic saturation and coercive force properties were done on sintered samples, which revealed reduction in both of these properties by increasing sintering time. No changing in density was observed.