| Copper radiator,which plays an important role in industry,has been replaced by aluminum radiator due to the lack of resources and other problems.However,aluminum radiator is facing the problem of low thermal conductivity.By cold spraying pure copper coating on the surface of aluminum,the material after spraying has both the portability of aluminum and the good thermal conductivity of copper.However,due to the poor wear resistance of pure copper coating,the wear loss is high in application.Therefore,in this paper,cold sprayed aluminum-based Cu/ceramic phase composite coatings were prepared by selecting different ceramic powders,meanwhile,the effect of heat treatment on the properties of the composite coating was studied,in order to obtain the aluminum-based Cu/ceramic composite coating with optimal thermal conductivity and wear resistance.This paper used Kinetic 3000 cold spray equipment and the cold spray equipment independently built by Northwestern Polytechnical University to prepare pure copper coating,Cu/Si C,Cu/Al2O3 and Cu/WC composite coatings.SEM,EDS,XRD,EBSD and white light interferometer were used to characterize the coatings.The performance analysis and numerical simulation were carried out by Image J,Image pro plus and Fluent software.At the same time,the basic mechanical properties,thermal conductivity and wear resistance of several groups of coatings were tested.The results showed that the deformation and porosity of the pure copper coating is reduced due to the recrystallization of crystal grains after 500? heat treatment,thus the thermal conductivity was improved.After the addition of the Si C and Al2O3 in the composite coating compacted the coating.The deposition content and Weibull distribution shape coefficient of the Cu/Al2O3 composite coating are respectively 10.5vol%and 9.036,and the Cu/Al2O3 composite coating had higher ceramic phase deposition efficiency and better distribution uniformity than the Cu/Si C composite coating.When the velocity of ceramic particles impacting the substrate reaches the critical value,the kinetic energy of ceramic particles impacting determines the deposition efficiency of ceramic particles,and the impact kinetic energy of the Si C and Al2O3 particles were respectively 2.763×10-6J and 9.164×10-6J,where the higher impact kinetic energy of Al2O3 particles contributed the higher deposition efficiency.The average Vickers hardness values of Cu/Si C composite coating and Cu/Al2O3composite coating were 166.8HV and 164.4HV,respectively,which were significantly higher than other coatings.Meanwhile,the nano hardness value of Cu/Al2O3 composite coating was2.247Gpa,which was the highest value among the composite coatings.The reason could be mainly related to the deformation uniformity of Cu particles.The distribution of ceramic phase in Cu/Al2O3 composite coating was more uniform,which caused the more uniform deformation of Cu particles and the increased nano hardness.The friction and wear stage of the four coatings can be divided into initial stage,running in stage and stable stage with the increase of cycle times.The main influencing factor of the wear resistance is deterimed by the different wear mechanism.The Cu/Al2O3 composite coating showed general adhesive wear and third body abrasive wear,and the average wear rate was the lowest,which was 70.88(×10-6mm3/Nm).Through EBSD,it can be seen that the copper particles in the wear scar section of the surface wear area changed from strip shape to fine particles under the action of stress.The average friction coefficient of Cu/Al2O3 composite coating after 500? heat treatment was 0.61,which is 0.17 lower than the cold sprayed Cu/Al2O3composite coating.In addition,the average wear rate of the Cu/Al2O3coating was reduced from 70.88(×10-6mm3/Nm)to 14.63(×10-6mm3/Nm)after 500? heat treatment,and the wear resistance of the coating was 19.79 times that of the pure copper coating.Compared with the coating without heat treatment,the wear mechanism did not change,but the wear degree of the two mechanisms was weakened.After 500? heat treatment,due to the recrystallization of Cu,the thermal conductivity increased from 156.911(W/(m·K))to213.482(W/(m·K)),which was higher than that of the cold sprayed pure copper coating.Therefore,the Cu/Al2O3 composite coating after 500? heat treatment showed the best thermal conductivity and wear resistance on the premise of meeting the highest ceramic phase deposition efficiency and distribution uniformity,which could meet the requirements of replacing pure aluminum radiator. |
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