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Preparation And Properties Study Of NiCrAlYSi/h-BN High Temperature Abradable Coatings

Posted on:2017-08-04Degree:MasterType:Thesis
Country:ChinaCandidate:G T YunFull Text:PDF
GTID:2371330566452845Subject:Materials Science and Engineering
Abstract/Summary:PDF Full Text Request
As the aircraft engine performance continue to improve,the performance of the engine components are put forward higher requirements.As an important part of improving engine comprehensive performance,abradable seal coating has been one of the important research directions of aeroengine.In this paper,In order to meet the demand of seal coating to improve the working temperature and further systematic understanding of wear and oxidation process,different proportions of NiCrAlYSi based high temperature abradable seal coatings were prepared by atmospheric plasma spraying system.CSM friction and wear test machine,CM1612BL type high temperature cycle furnace,SEM,EDS and other equipment and technology were used to test and analysis the coatings’properties,such as mechanical,friction and wear,high temperature oxidation,the main results were as follows:(1)The NiCrAlYSi/h-BN/PHB abradable seal coatings had uniform microstructure and the tensile strength of the coatings are more than 15MPa,the combination between coating and matrix was good.When the content of h-BN increased from 2%to 8%,the bond strength of the coatings decreased by 30%38%.When the content of PHB increased from 6%to 13%,the hardness of the coatings decreased by 1315.8(HR45Y),the porosity increased by about 6%15%,and the bond strength decreased by 17%39%.(2)The room-temperature average friction coefficient between NiCrAlYSi/h-BN/PHB seal coating and DD6 alloy ball was higher than the average friction coefficient at 800℃.For example,the room-temperature average friction coefficient of the ninth sample was 0.897,the average friction coefficient at 800℃was 0.425.The room-temperature wear mechanisms of NiCrAlYSi/h-BN coating were smearing,particle wear and slightly tribo-oxidation;the high temperature wear mechanisms were cutting,plastic deformation,tribo-oxidation and adherence wear.(3)The wear performance of the coating at 800℃was good,which was due to the soften of metal matrix phase,h-BN lubricant material and the formation of metallic self-lubricant oxide at high temperature.The increase of h-BN and PHB can effectively reduce the wear of coating and DD6 alloy ball,and the seal coatings exhibited excellent wear performance at high temperature.(4)With the constant 1100℃isothermal oxidation,the abradable seal coating surface unstable NiO and spinel phases gradually flaked or be replaced,formed dense and continuous oxide film,which was composed of inner layer of Cr2O3,outer layer of NiCr2O4 and Y,Si enriched elements.The oxidation process of coating internal pores were different from coating surface,formed oxide film around the pores with outer Cr2O3+inner(Cr,Al)2O3 double-layer structure.The oxide stringers grew into the(Cr,Al)2O3 composite films which were formed during atmospheric plasma spraying process.(5)The oxidation dynamic curves of the NiCrAlYSi/h-BN/PHB abradable seal coatings are index forms,and oxidation process can be divided into two simple processes:fast oxidation stage,slow and stable oxidation stage.The increase of h-BN and PHB can effectively increase the weight and the rate of oxidation.(6)Within the range of research,the mechanical properties,friction and wear properties and high temperature oxidation resistance of the 6#sample were better,comprehensive performance was best;the mechanical properties,friction and wear properties of the 9#sample were best,but the high temperature oxidation performance was not good.
Keywords/Search Tags:plasma spray, NiCrAlYSi based seal coatings, mechanical properties, friction and wear, isothermal oxidation
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