Study On Preparation And Performance Of Al₂O₃-Based Composite Ceramic Coating

The corrosion failure of high-temperature sand-bearing and high-pressure water injection pipelines,is an important factor affecting oilfield safety and efficient production.The Al₂O₃-based ceramic coating is a potential to solve the problem,thanks to its high hardness,high temperature resistance and corrosion resistance.However,the high porosity and low toughness of ceramic coatings lead to pipeline protection failures,restricting its development in industrial production.Therefore,optimizing the ceramic coating formulation to improve the porosity and toughness of the coating,thereby inhibiting or slowing down the corrosion process of the pipeline,has important theoretical value and practical engineering significance.Based on the Al/Fe₂O₃ reaction system,this paper prepared Al₂O₃-based ceramic coatings in situ in steel pipes by centrifugal self-propagating high-temperature synthesis technology.Through material performance tests,the effects of SiO₂ and SiC whiskers on the microstructure,phase,mechanical properties and corrosion properties of the ceramic coating were studied respectively,and the anti-corrosion mechanism of SiO₂ and SiC whiskers was clarified.Finally,the optimal formula of ceramic powder was obtained.The effect of SiO₂ on the structure and properties of Al₂O₃-based ceramic coatings was studied.The results show that when the addition amount of SiO₂ was 4 wt.%,the density of the ceramic coating reached the maximum and the porosity was the minimum.It was because the introduction of an appropriate amount of low-melting phase SiO₂ reduced the cooling rate of the system,and the gas in the liquid phase had sufficient time to discharge,so that the porosity of the coating was reduced.At this time,the ceramic coating exhibited better mechanical properties and corrosion properties.Based on the effect of SiO₂ on the densification behavior of ceramic coatings,a corrosion mechanism model was established.A proper amount of SiO₂improved the pores and interlayer gaps of the ceramic layer,reduced diffusion channels,prevented corrosive ions from entering the surface of the metal substrate and further diffusion,thereby improving the corrosion resistance of the ceramic coating.The effect of SiC whiskers on the structure and properties of Al₂O₃-based ceramic coatings was studied.The results show that when the addition amount of SiC whisker was 0.5 wt.%,the ceramic coating had significant strengthening and toughening effects,including tearing edge toughening,whisker bridging toughening and crack deflection toughening.At this time,the ceramic coating showed better mechanical properties and corrosion properties.Based on the effect of strengthening and toughening of SiC whiskers,a corrosion mechanism model was established.The strengthening and toughening mechanisms such as whisker bridging,crack prevention,and crack deflection hindered the generation and propagation of cracks,preventing corrosive substances from reaching the surface of the metal substrate effectively,thereby obtaining better corrosion resistance.