The Prepared And Study Of Composite Sealing Layer For Plasma Spraying Coating

Plasma spray coating technology is widely used in surface engineering for its quick forming speed, coating material variety, good coating performance, wide application and low cost. But the porosity is inevitable in the sprayed coating because of its inherent nature. The presence of porosity would decrease the corrosion resistance of coatings, so sealing treatment necessary in order to improve the corrosion resistance of the coatings. There are many ways of sealing treatment, of which sealing agent is among the commonest, such as microcrystalline wax, vinyl resins and other organic sealing agent, but they can’t used at high temperature and they have volatile and flammable, so the scope of their applications is limited. Therefore, the study of inorganic sealants have been developed rapidly in recent years.In this paper, we developed a new type of SiO2-Al2O3sol sealing agent by sol-gel method, and films were obtained by dip-coating method sealing. The structure and thermal stability of sealing layer was analyzed by XRD, IR, TG-DTA and SEM. The corrosion resistance, high temperature performance and anti-fouling properties were analyzed by full immersion corrosion test, high temperature oxidation test and the contact angle test.The results showed that the new inorganic amorphous SiO2-Al2O3sol sealing has good thermal stability. The SEM and porosity test results showed that the porosity of coating was significantly decreased after the sealing treatment, and the coatings density was significantly increased. The SEM and the EDS mapping of the polished cross-section showed that the sealant have excellent permeability and sealing ability. The corrosion resistance test of the seal coatings showed that the resistance to acid, alkali and salt was improved over50%compared with that of unsealing coatings. The high temperature oxidation test results showed that the oxidation resistance has been greatly enhanced after sealing treatment. So the protection of coating on matrix is intensified by coating sealing reagent.The contact angle is83.8°after the sealing treatment only with inorganic sealing agent, and the contact angle is101°after inorganic-organic composite sealing treatment, so the coatings with composite sealing treatment plays a better role in anti-fouling. The corrosion test results showed that the corrosion resistance improved over27%after inorganic-organic composite sealing treatment compared with that inorganic sealing treatment, so composite sealing layer can not only reduce the surface energy, play a role in pollution prevention, but also play a further role in sealing.