Preparation And Performance Of The Corrosion-resistant Oxide Ceramic Coating On Stainless Steel Surface

Metal-based ceramic coating with excellent heat resistance,corrosion resistance,high temperature oxidation resistance,high hardness and wear resistance on the metal surface can significantly improve the overall performance of the matrix metal.It makes the matrix not only has the good physical and mechanical properties of the metal,but also has the excellent characteristics of ceramics such as high temperature resistance,abrasion resistance,corrosion resistance.Therefore,the metal-based ceramic coatings are widely used in aerospace,machinery,electronics and other fields.In this paper,using sodium silicate?Na₂SiO₃?as a binder,and SiO₂,MgO,Al₂O₃,Na₂O powders as the ceramic aggregate,the enamel-coating was prepared on the 316L stainless steel substrate by the slurry method.The influence of the microhardness,thermal shock resistance and corrosion resistance of ceramic coatings under different technological parameters were investigated.The main results are as follows:Using SiO₂,MgO,Al₂O₃,Na₂O powders as the ceramic aggregate,and sodium silicate?Na₂SiO₃?as a binder,the process of preparing the ceramic coating by the slurry method and the influence of coating process and sintering process on the surface quality and microstructure of ceramic coating during the preparation process was studied.The results show that when the oxide powder passes through a 200-mesh sieve and the ratio of ceramic aggregate to binder is 1:15?g:mL?,a suitable slurry can be obtained;spray gun is used to ensure that the thickness of the coating is 100-150?m At a heating rate of 3°C/min,a coating with good performance can be obtained.A good performance coating can be obtained under the condition that spraying with a spray gun ensures that the thickness of the coating is100-150?m and the heating rate is 3°C/min.When the sintering temperature reached 750?,four chemically stable and corrosion-resistant phases,that were Al₂SiO₅,3Al₂O₃·2SiO₂,Ca₂SiO₄,Mg₂Al₂O₅,were formed in the coating.When the sintering temperature was increased from 600?to 800?,the microhardness increased from 65 HV to 371 HV.When the sintering temperature increased from 600°C to 750°C,the self-corrosion potential of the ceramic coating increased from-0.530 V to-0.379 V,and the self-corrosion current density was reduced from 26?A to 5.6?A,which indicated the enhanced corrosion resistance of the ceramic coating.After 20 times thermal shock resistance experiments at 700?,the ceramic coating sintered at 750?did not fall off,which insured a good thermal shock resistance and good combination with the matrix.The effects of addition of CaO and TiO2 on the microstructure and properties of ceramic coatings were further studied.The results showed that with the addition of trace element CaO,new phases of Ca₂SiO₄ with stable chemical properties and corrosion resistance were formed on in the ceramic coating,which promoted the corrosion resistance of ceramic coating.The self-corrosion potential of the ceramic coating is higher than that of the stainless steel substrate,and has a better protection effect on the substrate.The addition of TiO₂ increased the pores in the coating,so the corrosion resistance of the ceramic coating was not improved,but the bonding force between the ceramic coating and the substrate was improved,and the coating could be heated for 20 times at 800? without falling off.