| Titanium alloy has the characteristics of low density,high specific strength,good corrosion resistance and excellent biocompatibility,and is widely used in the fields of ships,aviation,chemical industry and medical treatment.But titanium alloy is prone to fretting corrosion when used in water-related equipment,and titanium alloy has poor oxidation resistance at high temperature.Therefore,it is of great engineering application value to study the low-cost surface treatment technology for oxidation resistance and corrosion resistance of titanium alloy.In this study,SiO2,Al2O3,MgO,CaO and B2O3 were selected as the main components of the coating,and sodium silicate was used as the binder.The ceramic coating was prepared on the surface of Ti-15-3 titanium alloy by slurry method.The phase structure,microstructure,corrosion resistance,high temperature oxidation resistance and mechanical properties of the coating were studied.The main results are as follows:Using SiO2,Al2O3,MgO,CaO and B2O3as main raw materials,and sodium silicate as binder,the composition ratio of ceramic aggregate and the influence of slurry preparation process on the surface and microstructure of ceramic coating were studied.The results reflect that when the coating is prepared,the coating is sprayed 2-3 times at 200-300 mm away from the surface of titanium alloy,so that the thickness of the coating is maintained at about 30?m.After spraying,the coating is dried and sintered at 750°C,and the dense and smooth ceramic coating with good bonding is obtained.By comparing the properties of the coating sample and the substrate,the results show that the wear resistance,corrosion resistance and high temperature oxidation resistance of the coating sample were significantly improved.In order to further explore the corrosion resistance of the coating,the coating samples and the substrate were immersed in 3.5%sea salt water for 15 days,30 days and 60 days,respectively.The microstructure,microhardness and corrosion resistance of the coating before and after immersion corrosion were studied.The results show that the coating is immersed in3.5%sea salt water.After 15 days of corrosion,pits appear on the surface of the coating,and the thickness of the coating is significantly reduced after 30 days of corrosion.After 60 days,the pits increase and become larger,but the coating and the substrate are still closely combined.After 60 days of corrosion,the coating's fracture toughness decreased from 3.75MPam-1/2to 2.45 MPam-1/2,and the microhardness decreased from 549.2 HV to 428.6 HV,but still greater than the microhardness of the titanium alloy substrate 399.3 HV.After 60 days of corrosion,the self-corrosion current of the coating was 0.32?A/cm2and the polarization resistance was 342.548 k?·cm2,while the self-corrosion current of the substrate was 1.32?A/cm2and the polarization resistance was 18.905 k?·cm2,indicating that the coating has long-term corrosion resistance.The effects of 10%,20%and 30%Cr2O3on the morphology,corrosive resistance and oxidation resistance in high temperature of titanium alloy coating was studied.The results show that with the increase of Cr2O3content in the coating,the number of Cr2O3elemental phases in the ceramic coating increases.When the Cr2O3in the coating is 10%and 20%,the coating is smooth and dense,and the oxidation resistance in high temperature of the coating is significantly improved.But,when the Cr2O3is more than 30%,the surface of the coating appears protuberance,and the microstructure becomes loose with the micro-cracks,and the protection ability is weakened.Because the addition of Cr2O3leads to large cavity defects in the coating,Cr2O3has no positive effect on improving the corrosion resistance of the ceramic coating. |
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