Preparation And Tribological Properties Of The Wc-co-ni Hard Alloy Mold Material

With rapid development of die & mold industry, the requirement for performance of die materials is higher and higher. Cemented carbide is used widely in the field of die machining because of its excellent hardness and wear-resistance. But with the speed of material molding rising, the requirement for cemented carbide performance must be improved. Therefore, the research and development of high-performance cemented carbide has importantly realistic significances.Nano-composites powder was made by high energy ball mill and then tungsten carbide with different binder content was prepared by sintering-HIP. The microstructure of prepared tungsten carbide samples was observed and compared by metallurgical microscope and SEM; the main mechanical properties of them were tested; the relationship among composition and microstructure and performance of them was studied and analyzed. Considering the special requirements of wear-resistance of die materials, the focus was on doing systemic friction-wear tests of prepared samples and studying the relationship between wear-resistance and composition of them. The worn surface of samples was observed and studied; then wear mechanisms and their affective factors and rules of tungsten carbides with different tribological property were discussed and analysed.The results showed that the content of cement (Co and Ni) of tungsten carbide would affect its microstructure, tribological property and wear mechanism directly. The sample with 19.5% content of cement had even microstructure, its wear-resistance best and its wear mechanism mainly adhesive wear; the sample with 7.5% content of cement had uneven microstructure, its wear-resistance worst and its wear mechanism mainly abrasive wear and brittle exfoliate. The wear mechanism of WC based cemented carbide varied with content of cement changing, high content of cement mainly adhesive wear while low content of cement mainly abrasive wear. The main reason of different wear-resistance of them was the different wear mechanism. Abrasive wear resulted worse wear-resistance.In identity condition, with the sliding speed rising the friction coefficient reduced and the wear rate increased. With the load rising, the friction coefficient of cemented carbide with less cement increased. But for the tungsten carbide with more cement, the friction coefficient varied complexly. That is because the wear mechanism changed with load increasing. The wear rate increased as the load increasing. But the content of cement could change the wear rate of tungsten carbide obviously, the main reason being different wear mechanism. The result also showed that the friction coefficient was affected with different fiction pair. The friction coefficient of friction pair WC-Co-Ni/Si3N4 was higher than WC-Co-Ni/GCr15 obviously.