The Method Research On Preparation Coating By Powder Electric Spraying On The Inner Surface Of Tube

Electric explosion is a new type of thermal spraying technology;using it high voltage pulse discharge on the spray material,also instantaneous high current through heat would induce heating and explosion,and then the particles were forced by shock waves and spraying onto the substrate surface to form a coating.The common electrical explosion spray method used in the current spray coating materials are mostly wire or foil,as most high-performance spray materials exist in powder form,the use of powder materials for explosive spraying has certain advantages.In the actual industrial production of a large number of pipe fittings need to be modified on the inner wall,such as spray guns in the barrel of the barrel of anti-ablative materials,chemical and oil pipeline wall spray anti-corrosion materials,automotive cylinder liner spray wear-resistant materials.Conventional spraying methods include flame spraying,arc spraying,and plasma spraying.The coating strength of the coating prepared by the conventional thermal spraying technique is low,and these spraying methods use high temperature flame flow to heat and accelerate the spray particles,which requires a large of the spray distance,which led to a larger size,it is difficult to extend into the tube on its inner wall of the spray.The explosive product has high temperature when preparing the coating,the formation of a coating releases a large amount of heat to melt the interface,with the matrix formed a micro-area metallurgical combination,greatly improving the coating and the matrix,coating and coating between the bonding strength.Moreover,during the explosion of the explosive process,the explosive product obtained a great speed under the action of the shock wave,without further aero solization,the spraying apparatus can be miniaturized,into the tube to achieve its inner wall of the spray.This paper designed and developed a set of tube for the inner wall of the powder explosive spraying device,the pure molybdenum powder was uniformly and quantitatively coated on the polyethylene load restraint rod,by the load restraint rod continuous and stable to the explosive tip of the two electrodes betwe en the explosion.To achieve the tube wall continuous powder electrostatic spraying,spray gun design into a round tube,make sure that the spray device can be inserted into the tube,the explosion chamber is made of polyethylene material with ablation eff ect,directional constraints on the explosive product,to achieve the direction of the tube wall spray.Pure molybdenum powder as the test of the spray material,in the case where the capacitance of the storage capacitor and the distance between the two e lectrodes are determined,the powder electrospinning test was carried out by changing the initial voltage,the powder coating amount and the spraying distance applied to the sprayed material.The experimental results show that the explosive products of the powder are composed of liquid particles with different particle sizes.The large particles(larger than 30?m)in the explosive products are sprayed at the rear end of the jet,and the small particles(less than 30?m)At the front of the jet stream,the large particles finally arrive at the surface of the coating.The size of the explosive product and the jetting speed are related to the parameters of the electric explosion process.The initial voltage and powder coating amount determines the energy density applied to the sprayed material.When the energy density is within the proper range,the coating surface is dense and uniform.The large particles account for about one quarter of the surface area of the coating.The initial voltage and powder coating amount determine the energy density applied to the spray material,the energy density in the range of 140~320J/mm3 when the coating is dense,the product of small particles,the surface coating of large particles of about four one point,the coating is dense and combined with the matrix metallurgy,the occurrence of elemental diffusion.When the energy density is greater than 320J/mm3 or less than 140J/mm3,the coating surface roughness is not easy to form metallurgical bonding,the surface covered with large particles coated more than half.Analysis of the coatings under different process parameters results in the fact that the energy density applied to the powder during the electrospray spraying process determines the large particle fraction of the explosive product and the binding of the coating to the substrate.The coating area obtained by different spraying distance has different characteristics.When the spraying distance is too small,the area of the coating is almost the same as that of the explosive nozzle,and the forming distance is uniform.The spraying distance increases,the coating area increases,When the spray distance increases to a certain extent,the matrix will appear bare.The electrical signals were measured at different initial voltages,it is found that the peak value of the current waveform of the sprayed material when the powder is electrically charged becomes larger as the initial voltage increases,The time of occurrence of an electric explosion will be shortened.Also found,after the initial voltage exceeds a certain value,continuous energy consumption of the powder coating process will be reduced,when the initial voltage is higher than 11 k V later,the utilization of energy in the process of electric explosion tends to be stable.