Research On The Structure And High Temperature Oxidation Resistance Of MCrAlY Coating By Arc Ion Plating

With the rapid development of the aviation industry,the inlet temperature of the engine is getting higher and higher,the working environment is getting worse,and the turbine blades are easily oxidized in the high temperature environment,which greatly reduces the service life of the blades.MCrAlY coating?M=Ni,Co or Ni Co alloy?is the second generation of high-temperature protective coating developed after diffusion coating,which can solve the problem of high temperature oxidation failure of turbine blades.In order to further improve the engine's working efficiency and meet the high-temperature working environment,Si,Ta and Hf are added to the MCrAlY coating,which significantly improve the coating's high temperature oxidation resistance,this research is a hot topic at home and abroad.Widely concerned by scholars at home and abroad,the arc ion plating technology is a relatively popular process technology for preparing MCrAlY coatings in recent years.Compared with conventional preparation technologies such as low-pressure plasma spraying and magnetron sputtering,it has the advantages of good metallization,high deposition speed,and strong bonding force.In this paper,the coatings of NiCrAlY,NiCrAlYSi,NiCoCrAlYTa and NiCoCrAl YHfSi are prepared on the surface of nickel-base superalloy DZ22B by arc ion plating.After the vacuum heat treatment of the coating,the samples were at 1050?,1100?and1150?,respectively.The temperature was oxidized for 200 h under constant temperature oxidation,.Through SEM,XRD and EDS and other detection methods,the morphology,phase and element diffusion law of the coating before and after heat treatment and oxidation process were analyzed to study the high-temperature oxidation resistance of coatings and compare the resistance to high temperature oxidation between different coating systems.experimental results show that:1.Vacuum heat treatment improves the microstructure of the coating,homogenizes the alloy composition,and makes the coating denser.After heat treatment,the phase transition of?-NiAl to??-Ni₃Al occurred.The mutual diffusion of elements occurs in the substrate and coating,which are the diffusion of elements such as W and Al from the substrate into the coating and the diffusion of elements such as Cr from the coating into the substrate..2.NiCrAlY coating forms a large amount of loose Ni Cr₂O₄ in the early stage of oxidation,resulting in a large amount of spalling of the coating.However,the oxide layer does not play an important role in Cr₂O₃ because of its high temperature oxidation resistance.It cannot prevent the oxygen infiltration process,resulting in internal oxidation of the coating and internal oxidation.When the oxidation temperature reaches 1150?,the coating completely fails and the substrate begins to be oxidized.3.The NiCrAlYSi coating forms a very uniform and dense?-Al₂O₃ protective layer in the early stage of oxidation,which prevents the diffusion process of oxygen into the interior of the coating and effectively protects the coating.When oxidized at 1100?,volatile CrO₃ is formed,and Cr inside the coating is protected by the?-Al₂O₃ coating and no oxygen reacted with it,and only the oxide?-Al₂O₃ is formed,showing excellent resistance to high temperature oxidation.4.The NiCoCrAlYTa coating can reduce the diffusion activity of Al due to Ta in the coating and slow down the consumption rate of Al in the coating.Therefore,the coating still has good high temperature oxidation resistance at 1100?.When oxidized at 1150?,the oxidation process is very severe and the Al in the coating is essentially consumed.Due to the low content of active elements,the role of the active elements is limited,and it is impossible to prevent the oxygen infiltration and internal oxidation.5.The NiCoCrAlYHf Si coating generates a large amount of acicular metastable?-Al₂O₃ in the initial stage of oxidation,and then transforms into a stable?-Al₂O₃,which enhances the high temperature oxidation resistance and effectively protects the coating.The active elements Hf and Si in the coating enhance the adhesion of the oxide layer,delay the peeling speed of the coating and reduce the loss of Al,so that the fresh surface exposed after peeling off of the coating can still form?-Al₂O₃,and the oxide protective layer still has a good protective effect on the coating.When oxidized at 1150?,Al is consumed in large amounts and it is impossible to prevent oxygen from diffusing into the inside of the coating and the inside of the coating iss oxidized.6.The high-temperature oxidation resistance of the MCrAlY coating is determined by the Al content and active elements in the coating.With high Al content,it can rapidly form a dense and uniform?-Al₂O₃ protective layer,preventing oxygen infiltration and reducing the oxidation rate.The incorporation of the active elements Si,Ta,and Hf can reduce the peeling speed of the coating and reduce the loss rate of Al.The NiCrAlYSi coating has the best anti-high temperature oxidation resistance and can be used on turbine blades at temperatures up to 1150?.