Effect of surface carburization on dynamic deformation and fracture of tungsten heavy alloys

Effects of surface carburization on dynamic deformation and fracture behavi or of tungsten heavy alloys were investigated in order to improve the penet ration performance. Dynamic torsional tests using a torsional Kolsky bar we re conducted on four specimens, three of which were carburized by the case carburization process. The test data were then compared with hardness, Char py impact energy, adiabatic shear banding, deformation and fracture mode, a nd penetration performance, With increasing carburization temperature and t ime, surface hardness increased, but impact energy decreased. The dynamic t orsional test results indicated that for the carburized tungsten specimens, cleavage fracture occurred in the center of the gage section with little s hear deformation, whereas shear deformation was concentrated at the center of the gage section for the conventionally processed specimen without carbu rization. The deformation and fracture behavior of the carburized specimens correlated well with the observation of the impacted penetrator specimens, i.e,, microcrack initiation at tungsten particles and cleavage crack propa gation. Since the cleavage fracture mode is thought to be beneficial for se lf-sharpening, these findings suggest the beneficial effect of the surface carburization on the penetration performance.