Study On The Influence Of The Form Of Y On The Performance Of MCrAlY Coating

With the rapid development of industry,the service condition of gas turbine becomes worse and worse.MCr Al Y coating has excellent high temperature resistance and corrosion resistance,which can be widely used in engine blades,gas turbine and other hot end components under complex working conditions.However,when the content of Y in NiCrAlY coating is too high or the high temperature oxidation service is long,Y₂O₃ will further form Y-Al-O oxide,which provides diffusion channel for oxygen.At the same time,the volume expansion and crystal transformation accompanied by this process will lead to the failure of the coating.In order to solve the above problems,changing the existing form of Y in the coating is the current research hotspot.According to the above ideas,this paper designed two schemes,namely,NiCrAlYcoating+embedding infiltration method Y to prepare NiCrAlY coating,and NiCrAlY coating prepared by NiCrAl/Y₂O₃ composite powder,to study the effect of different Y addition methods on the performance of the coating.The effects of the components of the embedding penetrating agent,such as catalyst,Y₂O₃ and its content,temperature and time,on the infiltration layer were studied.The microstructure and composition of the infiltration layer were analyzed by scanning electron microscope(SEM)and energy dispersive spectrometer(EDS).The high temperature oxidation behavior of NiCrAlY and NiCrAl/Y₂O₃ powders was studied by TG.The influence of the existing form of Y on the properties of the coating was discussed.The results are as follows:(1)The influence of embedding infiltration process on the performance of infiltration layer was studied,and the preparation process of infiltration layer was determined.The effect of catalyst type and content on the infiltration layer was studied.When the catalyst was Na F,Y obviously penetrated into the infiltration layer;When the content of Na F increases from 3 wt.%to 8 wt.%,the infiltration amount of Y increases from 0 at.%to 1.48 at.%,and the microstructure is more compact.Further increasing the content of catalyst will reduce the infiltration amount of Y.The effect of Y₂O₃ content on the infiltration layer was studied.When the Y₂O₃ content increased from 3 wt.%to 5 wt.%,the infiltration amount of Y in the infiltration layer could be effectively increased.At this time,the infiltration amount of Y reached 2.2 at.%,but when the Y₂O₃ content further increased to 7 wt.%,the infiltration amount of Y decreased.The effect of embedding temperature and time on the infiltration layer was studied.It was found that the amount of Y infiltration first increased and then decreased with the increase of temperature,and the optimum temperature was 1150?;When the holding time was extended from 4 h to 6 h,the amount and depth of Y infiltration increased significantly.The optimum preparation process was determined as follows:5%Y₂O₃-8%Na F-87%Al₂O₃,1150?and 6 h.(2)The high temperature oxidation properties of NiCrAl,NiCrAl0.5Y and NiCrAl1.0Y coatings prepared by low pressure plasma spraying at 1100?for 100 h were studied.The surface morphology and oxidation dynamic curve of the coatings were analyzed,and the effect of Y Content on the oxidation resistance of the coatings was obtained.The results show that the oxide film formed on the surface of NiCrAl coating falls off and the oxidation resistance is the worst;However,the oxidation weight gain of NiCrAl0.5Y coating is lower than that of NiCrAl1.0Y coating.Therefore,the oxidation resistance of NiCrAl0.5Y coating is the best.(3)The difference of oxidation resistance between NiCrAlY coating and thermal sprayed NiCrAlY coating with the same amount of y was compared.The experimental results show that the oxidation resistance of NiCrAlY coating is better than that of thermal sprayed NiCrAlY coating with the same amount of Y.In particular,the initial oxidation rate of NiCrAl/1.0Y coating is fast,and the oxidation weight gain tends to be stable after a long time of oxidation,while the oxidation weight gain of NiCrAl/1.0Y coating is about 3 times that of NiCrAl/1.0Y coating after continuous oxidation,Y exists in the coating in the form of intermetallic compound,which prolongs the transition time from y to Y-Al-O oxide and prolongs the service life of the coating.(4)The effect of different amount of Y on the performance of infiltrated layer was compared.The infiltrated layer was prepared on NiCrAl coating,NiCrAl0.5Y coating and NiCrAl1.0Y coating with 5%Y₂O₃-8%Na F-87%Al₂O₃(wt%).The infiltrated layer was oxidized at 1100?for 100 h.The results show that NiCrAl0.5Y coating has the lowest oxidation weight gain and the best oxidation resistance.The results show that the oxidation weight gain of NiCrAl0.5Y coating is 3.6 times that of NiCrAl0.5Y coating.Therefore,the oxidation resistance of NiCrAl0.5Y coating can be effectively improved after y-infiltration.(5)NiCrAl/Y₂O₃ powder was prepared by mechanical alloying method.The oxidation resistance of NiCrAl0.5Y powder and NiCrAl 1.5 Y₂O₃ powder with the same content of Y after oxidation at 1100?for 100 h was compared.The results show that the oxidation weight gain of NiCrAl/1.5Y₂O₃composite powder is significantly lower than that of NiCrAl0.5Y alloy powder with the same amount of Y.the oxidation resistance of NiCrAl/1.5Y₂O₃ composite powder can be significantly improved by introducing Y into Yttrium oxide(Y₂O₃)powder It has good performance.