Study Of Preparation And Properties Of Abradable Composite Seal Coating Used In High Temperature

Recently, the aeroengine known as heart of aircraft is put forward higher requirement with the rapid development of aviation industry.The engine designers is still unremitting pursuiting good performance of big thrust,high esteem,high efficiency and low oil consumption. Research shows that adopting seal technology, improving seal system and reducing gas leak are the most effective method of improving engine performance and reducing maintenance cost.The paper described main engine gas seal technologies especially abradable seal technology at home and abroad. The development status of seal coating materials is introduced.Because of characteristic requirements of seal coating with high temperature resistant, abradable property and anti-erosion, we chose nano Y2O3 partially stabilized ZrO2(YPSZ) as base-phase,nanoα-Al2O3 as conglutination-phase,micron-level hexagonal BN(hBN) as solid lubricant and polyester as pore-making materials respectively.Abradable seal coating materials were prepared by spray drying process.Then double-layer structure and gradient structure composite seal coatings were obtained by air plasma spraying(APS) process.Several coating materials and composite seal coatings were tested and analysed. Main conclusions were as follow:(1)The raw materials components in the seal coating powders were fairly well-distributed.The seal coating materials,hollow and round,were used well.(2)The raw materials components in the seal coatings were also fairly well-distributed.hBN was wrapped well in base-phase,and polyester was burned away,leaving a uniform distribution of porosity in seal coatings.Al2O3 was melted well and existed in lamella style of structure.ZrO2 had three melting state,which were melting,semi-melting and non-melting and existed in lamella or loose particles style of structure.(3)If coating materials had conventional polyester,there was hardly any polyester in corresponding coatings.If coating materials had large particles of polyester or covered polyester, there was some polyester in corresponding coatings.The left polyester in seal coatings formed many tiny holes,which could reduce hardness of seal coatings and improve abradable property.(4)The more content of Al2O3,the more dense of coating,the lower coating porosity,and the higher hardness and bonding strength of coatings.Coating 4 had more porosity,lower hardness and bonding strength than Coating 1.Coating 5 had more porosity,lower hardness and bonding strength than Coating 2.(5)In composite powder, ZrO2 existed in tetragonal and cubic structure styles and Al2O3 existed in a-phase.In seal coating, ZrO2 existed in tetragonal and cubic structure styles and Al2O3 changed fromα-phase for amorphous.After thermal shock experiments,ZrO2 existed in tetragonal structure styles and Al2O3 changed from amorphous for a-phase.(6)The more content of Al2O3,the poorer property of thermal shock.Because of adding a transitional lawyer between metal bond lawyer and ceramic lawyer,the gradient structure composite seal coating had the best thermal shock performance.(7)The coatings were sintered, the organization became dense,and the hardness became great in 1000℃high-temperature experiment.