Impact Fatigue Property Of WC-Co Cemented Carbides For Stamping Dies

There are many components which were worked under the repeated impact load and failed by impact fatigue in project. Stamping die WC-Co cemented carbide was one of them. Research about impact fatigue and fatigue data processing of cemented carbides were very few at home and abroad. The impact fatigue behavior of5kinds commercial cemented carbides were tested by small energy multiple impact destruction experiment in home-made impact fatigue system. Main conclusions are as follow:1^3kinds of cemented carbides201#、202#and203#were tested in different impact energies and different impact frequencies. In low-cycle fatigue, the higher bending strength was, the greater the impact life time; in high-cycle fatigue, the finer the grain size was, the greater the impact lifetime.201#is uitable for using in low-impact load and high frequency stamping condition;202is suitable for high-impact load stamping condition. The impact fatigue life decreases when the impact frequency increases from1Hz to4Hz:lifetime decreased50%as the impact energy is2J and20%as1J.2、5kinds of cemented carbides were tested in the same impact condition to acquire10fatigue life dates. The fatigue dates were analyzed by Normal distribution, Log-normal distribution and Weibull distribution. Correlation coefficient of Weibull distribution is the largest whether the impact fatigue data is less as10or more as50.Weibull distribution is a useful evaluation method of cemented carbides impact fatigue life and the dispersion of its properties.3、The impact fatigue performance of WC-20wt%Co cemented carbides with average grain size of1.4μm achieves the best. The average impact times and characteristic lifetime both are the largest; Weibull modulus reaches4.13, verifies the most centralized distribution dispersion4、Three distinct areas were observed at impact fatigue fracture e surfaces which including stable crack growth region of micro-size, bright field of rapid propagation and smooth area of final fracture. Compared to the general fatigue fracture, fatigue striations could not found in impact fatigue fracture. The bending fracture surfaces is smooth than the impact fatigue surface. The scale and roughness of bright field of crack rapid propagation is the difference for bending and fatigue fracture. Impact fatigue crack originated at defect in surface or subsurface. The crack expansions were mainly through the WC/WC and WC/Co interface. The fracture morphology of the best impact fatigue performance has a significant plastic deformation, which reflects the effect of the binder.