Study On The Machinability Of Green Cemented Carbide

Cemented carbide has been hailed as the “tooth” of industry for its series of merits, such as high hardness, good abrasion resistance. But the poor processing performance restricted its application, the processing methods is limited, mainly take milling and non-traditional machining. In this paper, the machinability of green cemented carbide is studied, that is machining parts before sintering. The advantages of this method is that: The strong atomic bonds that exist between particles, as well as hard phases, have not yet been formed before sintering, green compacts come only from cold welding and mechanical interlocking between neighboring particles. The cutting forces and the temperature in the cutting zone kept to a minimum, produces less heat and less wear while allowing an increase in productivity. It can solve some problems such as dimensional and shape are restricted, high cost, extend applications range of cemented carbide.In this paper, the green cemented carbide are made by pre-sintering, then turning and milling separately.Discussion the machinability of green cemented carbide by analyzing experimental data, electron microscopic observation, and the surface roughness measurement of machined surface. Sintering all the specimens, for machined and un-machined in green, compare the sintering properties of both series of samples, study the effect of green machining process on sintering behaviors. The main conclusions are as follows:(1) For the pre-sintering components, when the pre-sintering temperature is880℃, the green strength is best for machining. The surface diffusivity and the bond stretch of particles of pre-sintering parts is not high at low temperature. When the sintering temperature is higher than950℃, the bond stretch of particles and the green strength increased rapidly.(2) The lathe rotational speed and federate influenced the green machining process, generally, the higher lathe rotational speed, the lower federate, the quality of the machined surface is better. The optimum machining process obtained in this paper is that the rotational speed at2000r/min, federate at0.05~0.02mm/rev.(3) There are some pits left by WC particles when they shed off on the surface and some discontinuous grooves on the differ direction about cutting direction. The analysis show that the mechanism of green machining is “cutting-drawing” mechanisms.(4) The structure integrity and surface roughness of the samples is quite different when they machined in different way. There is some light breakage exist in the last edge seen by the cutting tool when the samples machined by turning, the structure integrity and surface roughness of the samples has improved significantly when they machined by milling.(5) Samples are sintered on the same condition, there is no adverse effect on the sintering performance of cemented carbide when machined in green, the result show that there is no crack and tiny crack produced during the machining process of green samples.