Study On Tungsten-Copper Coating And Tungsten-copper Functionally Gradient Material Prepared By Explosive Compaction-Welding Sintering

Explosive compaction-welding sintering method is a new explosive processing method,which combines explosive compaction,explosive welding and diffusion sintering.It has characteristics of simple device,high efficiency,high density and high bonding strength of the prepared coatings.It is an explosive processing method with broad application prospects.In this paper,W-Cu material is taken as the research object,the technical method of explosive compaction-welding sintering and the macro-mechanism and micro-mechanism of this method are deeply studied.Firstly,technological process of explosive compaction-welding sintering is introduced,and basic principles of reduction sintering,explosive compaction-welding and diffusion sintering are given.In principle of explosive compaction-welding,it is pointed out that in order to obtain high quality coatings,it is necessary to realize compaction of coatings,welding between coating particles and welding between coating and substrate.As long as pressure reaches the condition of explosive welding of powder in coating,explosive welding can take place between coating particles and between coating and substrate.Calculation methods of pressure required for explosive compaction of coating and explosive welding of powder in coating are given.It is suggested that the higher pressure of above two pressures should be chosen as the pressure required for explosive compaction-welding.Secondly,W-Cu coating is prepared on inner surface of copper cone cover by explosive compaction-welding sintering,it's proved that this method can not only prepare coating or:n surface of plate,but also on surface of abnormal structure.No impurities are introduced during preparation of the coating,distribution of W and Cu in the coating is uniform.The effects of tungsten particle size,tungsten content and detonation velocity on explosive compaction-welding are studied.W-Cu coating is prepared on surface of copper substrate by underwater explosive compaction-welding device,which made it possible to prepare large-scale coating materials.High density W-Cu gradient material is prepared by this method,It is found that this method can avoid growth of tungsten particles in W-Cu coating when tungsten content is low,but when tungsten content is high,the growth of tungsten particles occurs.The reason for the growth of tungsten particles is the sharp rise of local temperature caused by intense friction between W-Cu particles under the pressure produced by explosion.Then,macro-mechanism of explosive compaction-welding is studied.A method for calculating porous mixture is proposed.Firstly,Hugoniot curve of dense mixture is obtained by the principle of mixture superposition,and then the Hugoniot curve of dense mixture is extrapolated by isobaric method to obtain Hugoniot curve of porous mixture.The Hugoniot curve of porous materials obtained by isobaric extension is substituted into numerical simulation.The macroscopic process of explosive compaction-welding is simulated by AUTODYN software,and the evolution law of shockwave in the coating can be obtained.It is found that incident angle of shockwave plays an important role in compaction-welding between coating and substrate through a loading experiment using flying plate.When normal shockwave is incident at high pressure,coating and substrate are separated.The reason for the separation of coating and substrate under normal incident shock wave is explained by using one-dimensional shock wave interface reflection principle.It is pointed out that the combination of coating and substrate is caused by internal collision between coating and substrate.Finally,micro-mechanism of explosive compaction-welding is studied.Experiments show that micro-connection modes of coating and substrate are explosive welding,friction welding,jet penetration and liquid phase sintering.SPH method is used to simulate closure process of micro-pore,and the results show that micro-connection modes obtain from numerical simulation are the same as that from experiments.Experiments show that diffusion sintering can eliminate internal defects of materials,and prove the existence of element diffusion between coating and substrate.