Investigation On CVD Parameter Regulation And Penetration Properties Of Large-diameter-pure Tungsten Shaped Charge Liners

The high density?19.3 g/cm³?,high acoustic velocity?4.03 km/s?and good ductility of W make it one of the most potential materials for shaped charge liners?SCLs?.Our research group obtained small-diameter-pure W SCLs by CVD.These SCLs got great penetration depth in the static tests.The penetration characteristics and penetration mechanism of SCLs were analyzed.During the actual process prepared large-diameter-pure W SCLs by CVD,the equipment failed to work or selected unreasonable deposition parameters,these problems made the surface quality and organization grains of SCLs coarser,therefore,the penetration power of SCLs significantly reduced.In order to refine the organization,investigate the penetration mechanism and enhance the penetration power of SCLs,the present work perfected CVD equipment,controlled the deposition condition,obtained large-diameter-pure W SCLs with refine grains.Through statically detonation tests and detailed microscopic analyses of recovered targets,this paper investigated the characteristic and mechanism of large-diameter-pure W SCLs.Studied the deformation mechanism of pure tungsten liner under explosion loading condition through the recovered slug.According to the requirements of CVD prepare large-diameter-pure W SCLs,this paper solved the pipe blockage problems,refined the surface quality and improved the thickness evenness of SCLs.Simplifying the design of pipe and using manual valves instead of one-way valves make the pipe work well.The gas flow of WF₆ is controlled in the range of 9¹2g/min by selecting matching needle,it prevents gas nucleation.It is beneficial to refine surface of SCLs and make the process safer,more environmentally friendly and more economical.The thickness evenness of SCLs is improved with fixing the heating wire by double stainless steel bracket.The optimized CVD parameter for large-diameter-pure W SCLs is obtained,the deposition temperature is 500?±10?,the flow of H₂ is 1800±50mL/min,the initial flow of WF₆ is 11.5g/min,adjusting the flow of WF₆ to 9.5g/min after 180min.The organization of large-diameter-pure W SCLs is refined by this parameter.Reducing the flow of WF₆ during the middle process can accelerate the reaction between H₂ and fluoride,it is conducive to re-nucleation and growth of tungsten atoms,the columnar transform into pseudo-dendrite and stop the columnar growth.Analyses of the characteristics of large-diameter-pure W SCLs show that,when the standoff is 2 times of the liner diameter,the penetration of the large-diameter-pure W SCLs is 656mm.The broken hole diameter of the target is large,the surface of the target is coarse and there are small changes between the target diameter.The poor fluidity of W makes sharp reaction between jet and target,high hard phase and martensite appear which lead to severe energy lateral diffusion,this is the reason the surface of target is coarse and the small changes between the target diameter.Further more,energy lateral diffusion reduce the penetration.Investigations of deformation mechanism of pure tungsten liner under explosion loading condition show that,there are all equiaxed grains in the slug,the whole diameter of the grains are too large,grain diameters are different,there are obvious differences between large-diameter-pure W SCLs and small-diameter-pure W SCLs.Severe plastic deformation of large-diameter-pure W SCLs during penetration process lead to generate equiaxed grains.The morphology of large-diameter-pure W SCLs is columnar coexisting with pseudo-dendrite,the diameters both organizations are different,and the subgrains belong to original organization rotate in different degrees during recrystallization,therefore,the whole diameter of the slug grains are too large and grain diameters are different.