Phase,Residual Stress And Hardness Analysis Of Aluminum-silicon Sealing Coating Under Thermal Cycling Condition

As one of the important factors affecting aero-engine,sealing coating can maintain the airway seal of the engine and effectively control the radial airflow clearance,and achieve the maximum pressure difference,so as to improve the engine efficiency and reduce fuel consumption.After experiencing the actual service conditions,the performance of the coating will change,which will affect the normal service of the coating.Therefore,it is very necessary to study the performance change of the sealing coating under the thermal cycling conditions.At present,plasma spraying technology is used in this paper to prepare aluminum-silicon sealing coating on Zg0Cr16Ni Cu3Nb(cast steel precipitated hardened stainless steel)with Ni₅Al as bonding layer.Using X-ray diffraction,Scanning electron microscope(SEM),Nano indentation technique,X-ray diffractometer and Vickers indentation technology research Al-Si seal coating under the condition of the thermal cycle of microstructure,porosity,residual stress and hardness change rule,analysis of aluminum and silicon seal coating under different heat treatment temperature and time of performance evolution mechanism.The main research contents are as follows:Firstly,The original Al-Si coating mainly has Al phase,Si phase and Al₂O₃ phase,and the diffraction peak of Al shifts to the right,while the diffraction peak of Si becomes wider.The coating structure is compact and each layer is closely bonded.After thermal cycling at 300?and 400?,there are obvious diffusion layers at the interface of some samples,and the diffusion of iron element towards the bonding layer is obvious.The cross section and surface porosity of the original Al-Si sealing coating are about 0.51%and 0.92%.With the increase of temperature and time of thermal cycling treatment,the grain growth of Si,the slip of phase interface,micro-crack propagation and creep in the coating lead to the increase of porosity.Secondly,The elastic modulus of Al-Si coating changes obviously.The residual stress of the original sample is 36.4 MPa.With the process of thermal cycling,phase slip,micro-crack propagation and creep occur in the coating,as well as the growth of Si grains,which make the elastic modulus change obviously,and the stress of the coating presents an overall upward trend.Thirdly,The hardness value of the sample was in the range of 28.74?175.31 HV.At 200?,300?and 400?,with the increase of thermal cycling treatment time,the hardness of the surface and section decrease at first and then change to be steady,and the hardness of the bonding layer generally increases.In the in-situ hardness test at high temperature,the hardness of Al-Si coating first increases and then decreases with the increase of test temperature.