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Designing for Carbide
Designing for Carbide requires special considerations in the area of selecting safety factors based on stress, toughness, impact and corrosion characteristics. Components should be designed within these parameters for optimum performance.
The Safety Factor
The selection of a safety factor from calculations of stresses, fatigue and load factors may not be sufficient in all cases. Thus, the selection of a safety factor relies on good engineering practices, applications knowledge and, when possible, computer modeling. Select a safety factor that is low enough to be practical, but large enough to accomplish the job.
The transverse rupture test is employed for measuring the resistance to normal stress for specific tungsten carbide grades. For design, it is advisable to consider the stresses to which a component will be subjected. Application of known stress reducing factors such as large fillet radii at corners and generous cross sections around holes will naturally lead to enhance load resistance.
Most impact energy is absorbed by the elastic structure of the material being formed; some energy is dissipated by heat and friction. When selecting a grade of tungsten carbide for an impact application, it is important to consider that its impact resistance is a function of its composition; grades of higher binder content will tend to have greater impact resistance. Also, it is vital in designing for impact application, to reduce or eliminate all stress raisers, which are potential sites of failure under shock conditions. Carbide material excels, when compared to tool steel, for impact applications.
Cemented carbide grades are far superior to steel counterparts in wear applications. The wear properties of cemented carbide depend on the grain size of the material. The lower the binder content and the finer the grain size, the better the wear capabilities. For particularly abrasive applications and where maintaining sharp edges is vital, submicron grades will benefit the user. Our expertise in manufacturing and the use of only high quality materials result in the production of superior wear grades; the ultimate advantage to the design engineer.
The Selection of material should involve consideration of the operating environment. While cemented carbides are superior to other metallic materials in corrosive environments, this does not mean that cemented carbides are totally inert. The cobalt binder in tungsten carbide is subject to attack, binder leaching, where chlorinated liquids such as city water are present. In such environments, the corrosion resistance of nickel bound grades is superior to cobalt bound grades. Federal Carbide produces many grades of tungsten carbide in both compositions.