Hardmetal Production

The preparation of a hardmetal specimen consists of several steps and can be performed along different paths. Basically, one may distinguish between three or four main steps  

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K. J. A. Brookes, World Director and Handbook ofHardmetals and Hard Materials, 5th ed.. International Carbide Data, East Barnet, Hertfordshire, UK, 1992. T. E. Chung, D. S. Coleman, A. G. Dowson, and B. WiUiams, eds.. Proceedings of the Pecent Advances in Hardmetal Production, Loughborough University of Technology, pubHshed by Metal Powder Report, Sept. 17—19, 1979. 

Although the above characterization in regard to physical and chemical properties seems to be quite rigid and complete, in some cases imexpected and unsatisfactory results may occur diuing the further hardmetal production. The reason for this behavior is based on still insufficient specification, because the carbon black quality, carburization temperature, as well as type and diuation of milling after carburization are not clearly defined, and can be changed by the supplier or may differ between diverse suppliers. 

FIGURE 9.23. Schematic flow chart for hardmetal production, showing the variety of production routes. 

Direct compacting is mainly used in producing mining tools, metal cutting inserts, and parts for construction applications. Around two-thirds of hardmetal production is compacted by this method. 

FIGURE 9.24. Representative sintering cycle of hardmetal production, indicating the different stages of sintering. 

FIGURE 9.25. Three-chamber vacuum sintering furnace for hardmetal production (Ipsen). By courtesy of WIDIA GmbH., Germany. 

Braiden,P,M,Failure criteria for WC-Co materials under multiaxial stress states or long term static stresses,In Conf.on Recent Advances in Hardmetal Production,Loughborough, 17-19 Sept.1979, 28-1. 

The preparation of TiC, VC, NbC, TaC, M02C, WC, and the chromium carbides are important technical processes for the production of carbide powders for hardmetals. Generally, the carbides are prepared by the reduction of oxides with carbon only M02C and WC are manufactured by reaction of the metal powders with graphite or carbon black. 

Manufacture ofhardmetals [9.4]. The manufacture of hardmetals is based on powder metallurgical techniques, which include several steps. Each step must be carefully controlled to achieve a final product with the desired properties. These steps are ... 

This chapter will follow the different stages of powder metallurgical manufacture. More emphasis will be put on the description of WC powder production methods and qualities, and the preparation of graded powders. Less emphasis will be put on sintering, hardmetal qualities, and applications. In this context, we refer to several excellent books and review articles dealing particularly with hardmetal technology, properties, and applications [9.1, 9.2, 9.4, 9.7-9.9]. 

The desired final carbon content of the WC powder depends on the further production mode of the hardmetal producer (mainly powder milling and sintering conditions), and varies between slightly understoichiometric to stoichiometric (6.13 wt%) to slightly overstoichiometric. 

The pressing dies (fabricated of hardmetal) are made to the shape of the desired end product, which means that the die must be greater to allow for shrinkage occurring during sintering. 

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