| Nowadays,natural resources are increasingly scarce,and people's awareness of environmental protection is increasing.Aluminum alloy has become the preferred material for lightweight products because of its excellent mechanical properties and lighter weight.Although Al alloys have excellent mechanical properties,its surface properties are poor,especially its wear resistance and corrosion resistance.Under this background,how to improve the various properties of Al alloy has become the top priority.In this paper,WC-10Co-4Cr wear-resistant and corrosion-resistant coatings were sprayed on 7A04 ultra-high strength Al alloy by HVAF high velocity air fuel technology.The effects of spray gun traverse velocity,spraying distance,step distance and powder feeding rate about coating quality were analyzed and compared.It includes the effect on the porosity of the coating,the microhardness of the coating-substrate interface and the adhesion between the coating and the substrate.Field emission scanning electron microscopy(FESEM)was used to observe the interfacial morphology of the coating-substrate and to make a preliminary judgment about the quality of the coating.Photoshop graphics processing software was used to analyze the internal morphology of the coatings captured by scanning electron microscopy and calculate the porosity of the coatings.The microhardness of coating-substrate interface was measured by microhardness tester.MFT-4000 multifunctional surface properties tester was used to test the binding force between coating and substrate.Finally,the sample was prepared according to the required sample size in the ASTM-C633 tensile method approved by international standards,and the coating prepared in this experiment was standardized by this method.The porosity of coating,microhardness of coating-substrate interface and bonding strength between coating and substrate were comprehensively analyzed.The optimum spraying parameters of WC-10Co-4Cr wear-resistant and corrosion-resistant coating prepared by HVAF high velocity air fuel technology on 7A04 ultra-high strength aluminum alloy under this working condition and gas flow condition were obtained.Through the above experimental analysis,the following conclusions are drawn:(1)When the transverse velocity of the spray gun varies in the range of 500 mm/s to 800 mm/s.The coating porosity at 500 mm/s and 600 mm/s is lower than that at 700 mm/s and 800 mm/s.The microhardness of coating-substrate interface and the bonding force between coating and substrate are larger than those at 700 mm/s and 800 mm/s.(2)When the spraying distance varies from 125 mm to 155 mm,the porosity of the spraying distance is 125 mm is close to the porosity of the spraying distance is 155 mm and larger than that of the other spraying distances in this range.When the spraying distance is 135 mm,the porosity of the coating is less than that of the other spraying distances,and the microhardness of the coating-substrate interface and the bonding force between the coating and the substrate are larger than those of the other spraying distances in this range.(3)When the step distance varies from 1 mm to 4 mm,the porosity of the step distance is 1 mm is close to the porosity of the step distance is 4 mm and larger than that of the other step distances in this range.and the microhardness of the coating-substrate interface and the bonding force between the coating and the substrate are lower than the other step distances in the range.(4)When the powder feeding rate from 2 r/min to 6 r/min,the porosity,microhardness of coating-substrate interface and bonding force between coating and substrate all show normal distribution.The powder feeding rate too large or small has great influence on the quality of coating.(5)In this experiment,the WC-10Co-4Cr coating sprayed on 7A04 ultra-high strength Al alloy surface by HVAF high velocity air fuel technology has good bonding with the substrate,and the coating quality is high.(6)By comparing the coating quality test results of the coatings sprayed with all the spraying parameters,the optimum range of spraying parameters under this working conditions and gas flow condition is obtained as follows:·Spray gun traverse velocity:500~600 mm/s·Spraying distance:135~145 mm·Step distance:2~3 mm·Powder feeding rate:3~4 r/min... |
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