Effects That Interface Aluminum Distribution On The Growth Of Thermally Grown Oxide And Thermally Cycling Tests In Thermal Barrier Coatings Irradiated By High Current Pulsed Electron Beam

Thermal barrier coatings?TBCs?is one of important surface engineering technology that increasing the service life of material hot parts,and the thermally grown oxide?TGO?is main part where TBC failure occur.There is an meaningful direction studying how to control the growth of the TGO to improve TBC performance.In this paper,using electron beam evaporation vacuum deposition?EBVD?and high current pulse electron beam?HCPEB?to make TBC interface alloy with aluminum film,to change the aluminum distribution of interface coating interface and to make the TGO growth under control.Finally,it can improve high temperature oxidation resistance and thermal shock resistance of TBC.Preparing double-layer TBC on high-temperature alloy substrate by atmospheric plasma spraying?APS?technology.Bonding coating and ceramic coating material are CoCrAlY and YSZ.Using EBVD and HCPEB technology in combination to make TBC interface alloy with aluminum film and by providing some kind of sand blasting process to promote interface bonding force after electron beam processing.Using the high temperature oxidation and thermal shock experiments to simulate the TBC service environment and to test the coating performance.Using scanning electron microscopy?SEM?,laser scanning microscope?LSM?,energy distribution spectrometer?EDS?and micro raman spectroscopy system?MRS?to test and characterize the original TBC and another kind,which improved with a variety of the surface modification technology,focusing on the interface and the growth behavior of the TGO,to explore the effect of interface aluminum alloying on the performance of TBC service,to establish a relations between aluminum content,TGO and service life of TBC,which provides the theoretical foundation for improving the service life of TBC.Original TBC had a rough interface morphology with a majority of sharp peaks and gullies.Ceramic layer was featured by lamellar structure with some holes,sharp corners,inclusion and micro-cracks inside it;Original TBC high temperature oxidation process had a three stages:?1?In early oxidation process,the oxidation kinetic curve obeyed linear regularity;The TGO layer around interface was thin and irregular,the thickness of TGO is about 1.42 microns and some parts of ceramic coating had micro cracks at interface.?2?In secondary process,the oxidation weight gain got slow down;TGO thickness was about 2.21 microns.The TGO began to be divided into 2 parts,which had generated gray mixed oxide Co2CrO4,Co3O4 and CoAl2O4.?3?Finally,it began to accelerate oxidizing and weight curve slope increased.The thickness of TGO was 3.4?m.A large number of longitudinal and transverse crack in the interface between TGO and ceramic coating.EDS results showed that the aluminum inside bonding coating layer,which near TGO was nearly exhausted.The early formation of TGO was Al₂O₃,and more TGO formed by spinel mixed oxide later.After 200 times thermal cycling,10% coating was flaked.The residual stress of the interface was about 10.94 MPa.The interface of TBC treated with aluminum alloying,under HCPEB,was uniform relative to the original coating.Those morphology,holes,sharp and cellular body formed into many micron discrete bulged nodules.Ceramic coating and bonding coating were in great combination.The high temperature oxidation process of TBC improved was similar to the original coating after treatment.However,the oxidation gain weight were lower than the original coating during all stages.In addition,TGO morphology was continuous and dense,and there did not have large crack and craze in TGO layer while some micro cracks and holes existed in the ceramic coating;According to EDS results,the aluminum content was relatively stable on the side of bonding coating,and didn't show the phenomenon that happened in the original coating.TGO composition was a single Al₂O₃ and did not have mixed oxide.After 200 times thermal cycling,the TBC was stable did not fall off and flaked off.The stress of TBC interface was about 7.59 MPa.