Study On The Technology Of Metal Matrix Composites By Thermal Spraying

The principle of arc spraying and plasma spraying technology and process were summarized.The influence of deposit structure,spraying parameters,bonding strength were investigated.And the bonding mechanism was discussed.Otherwise,through control the spraying atmosphere,the oxidation can be reduced on particle surface.Composite sprayed in controlled atmosphere is more compact,less oxidized and higher bond strength so can be used to produce special capability materials.By plasma equipment spraying powder materials,with the spraying distance of 100mm,arc current of 400A,Test the performances of arc voltage and the flow of powder feeder.The results indicate that arc voltage is the most influential factor for the microstructure and properties of the deposit,the optimized spray parameters are:primary gas(Ar) flow rate of 1.9m³/h,auxiliary gas(H₂) flow rate of 0.2m³/h,arc current of 400A, arc voltage of 65V,powder feeder gas flow rate of 51/min.Using arc spraying Al,4Cr13 metals,gray Al₂O₃ ceramics powder and NiWC35 alloy powder by plasma spraying to prepare metal and ceramic composites.The research show that have obvious slice layer structure,Al₂O₃ powder particles flatting obviously, well-distributed in base materials,add the macro hardness,abrasive resistance,heat resistance of aluminum;when spraying WC NiWC35 alloy powder,WC hard phase homogeneous distribution into Ni alloy melt,and due to high temperature of plasma spraying,some WC were broke down and melt of Ni metal,distribution to melt generatrix, thus formed the metallurgical combination.But these two kinds of deposits were found some defects such as holes,micro cracks,unmelted grains,need follow-up processing.The 4Cr13,Al,Ti single material,3Cr13/FeCrAl,FeCrAl/70steel,7Cr13 flux cored wire "pseudo-alloy" material sprayed in air and controlled atmosphere by arc spraying are compared,and it is showed that there are many oxidation coating between the grain of microstructure sprayed in air,thus,grain diffusion and continuity of metallurgical reaction are destroyed,prevent the particle from growing through grain boundary to achieve the metallurgical bond.This is the most significant factor to reduce the bond strength.Microstructure sprayed in controlled atmosphere(Ar) is little oxidation,no obvious layered structure.However,there exist a number of pores.Parts between grains which there are no pore have grown to co-grain.Metallurgical bond has taken place.