Powder injection molding is advantageous for hard metal components with complex shapes or large h/d. In the production of cemented carbide by powder injection molding, the change in the carbon content of the alloy is greater due to the higher content of the moulding agent than in conventional die molding.
The carbon content in cemented carbides is a key factor in determining the properties of alloys. In general, carbon content is controlled by the composition of raw material, the atmosphere of thermal degreasing and the atmosphere of sintering.
Kim Song Il, a researcher at the Faculty of Materials Science and Technology, has succeeded in forming η phase on the microstructure by controlling the binder content and the solvent parameters of debinding process in WC-8Co hard alloy, which leads to the prolongation of life of alloy and cost reduction.
He studied the effect of binder content on the property of products by measuring the carbon content, shrinkage, hardness, transverse rupture strength (TRS) while changing the binder content between 40 and 50vol%. He performed solvent debinding in the mixed solvent of benzole and acetone in the ratio 3:2 at an extraction temperature of 45℃ with an immersion time of two to six hours. Thermal debinding was conducted together with sintering, and the final sintering was done at 1 450℃.
The hardness value and TRS were HV1 560 and 1 580MPa respectively, and the service life was extended by 1.3 times.
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