W-Cu Composites Prepared By Cold Spraying And Mechanical Performance Research

W-Cu composite materials are widely used in electrical industry, electronic packagingand military industry and other fields due to its high strength, good electrical and thermalconductivity. Since W and Cu cannot dissolve each other in solid state, the powders of Wand Cu are mixed and sintered at high temperature to prepare W-Cu composite. However, itis difficult to fabricate the thin-walled parts with complex shape using traditional powermetallurgy processing. And the new preparation methods are in progress due to its high costand low efficiency.In this paper, pure Cu and W-Cu composite coatings were prepared by cold sprayingand were heat treated in vacuum. The microstructure evaluation of coating was studied. Thequasi and dynamic mechanical properties of composite coating were tested by conductingquasi and dynamic load. The influence of heat treatment on mechanical properties wasinvestigated. Using the commercial software of MATLAB and ABAQUS, a method ofcreating model based on real microstructure of W-Cu coatings was determined. Finally,the relationship between microstructure and mechanical property of coating was discussedbased on computational mechanical micro-models.The results show that the propulsion gas is the main factor which can affect thedeposition efficiency, density and mechanical property of coatings. Coatings prepared withhelium performed higher deposition efficiency and density as well as better properties thanthat with nitrogen gas. After post heat treatment, particle boundary of Cu disappearedpartially and some equiaxial grains were observed. As the pores in W-Cu coatingsdisappeared gradually, the density of coatings increased at the same time.The mechanical property of copper coating shows that there exist significantwork-hardening in as-sprayed coatings. Moreover, the yield strength of coating sprayedwith helium is higher than that with nitrogen. After heat treatment at400°C for1h, thework-hardening effect was eliminated. The remained difference of dynamic mechanicalproperty between coating and bulk material can be attributed to the typical multi-interfacemicrostructure of cold-sprayed coating. As for the W-Cu composite coating, the yieldstrength under both quasi static and dynamic loadings increased with the increase ofsintering temperature. The yield strength of W-Cu coatings under dynamic load is higherthan quasi static load. By programming with MATLAB and ABAQUS, the method of FEM modeling basedon the realistic microstructure of W-Cu composite was founded. The distribution andcontent in FEM model is consist with the statistical result of SEM picture. The simulationresults show that obvious stress concentration can be observed in W particles. Thesimulated result is consistent with the tested data of W-Cu coating after400°C heattreatment with an error of about12.5%and3%for yield strength under quasi static anddynamic loading，respectively. The simulated maximum stress performs errors of15%and3%comparing with the tested one under two conditions. The size of pictures has nosignificance influence on the simulated results.