| The addition of Al in the aircraft fastener coating CrN coating can improve the high temperature resistance and corrosion resistance of the coating and better adapt to the severe working environment.In this paper,Cr-CrN-CrAlN coating and Cr-CrN alternating coating were prepared on the surface of Ti-6Al-4V by MF-DC combined magnetron sputtering system.The mechanical properties,high temperature resistance and corrosion resistance of the two coatings were compared.The main research results are:Firstly,magnetron sputtering system was used for preparation of CrN alternating coating and CrAlN coating by PVD1012 vacuum coating machine.The CrAlN gradient coating has a compact columnar structure,and the grains are elongated in the growth direction,and the total thickness of the coating is about 2.8?m.The surface roughness of the CrAlN coating is 24%lower than CrN coating.The addition of Al element refines the grain of the CrAlN coating,the surface state of the coating is greatly improved,the surface is dense,and the roughness is reduced.The critical load Lc of the CrAlN coating was 39.1N,which was 10.5%higher than that of the CrN sample.This indicates that the CrAlN coating has better anti-blocking failure than the CrN coating,and the CrN coating is more brittle.The hardness and modulus of the CrAlN coating were higher than CrN coating.The hardness of the two coatings generally decreased with the increase of oxidation temperature and oxidation time.The hardness of CrAlN coating decreased slowly while the hardness of CrN coating decreased greatly and eventually failed.The high temperature resistance of the CrAlN coating with Al added was significantly higher than that of the CrN coating.CrAlN coating at high temperature produces a mixed oxide of Cr2O3 and Al2O3,which is denser than a single Cr2O3 or Al2O3 structure.The complete oxidation temperatures of the CrAlN and CrN coating were:850°C and 750°C.The growth rate constant of the CrN coating is significantly greater than that of the CrAlN coating.The activation energy Ea value of the CrAlN coating sample is 48.5%higher than that of the CrN sample,and the CrAlN coating with high Ea value is less prone to oxidation reaction.The corrosion potential Ecorr value of the CrAlN coated sample was shifted to the positive side compared to the CrN coated sample.The positive offset of Ecorr indicates an increase in corrosion resistance,the corrosion resistance of the CrAlN coating is superior to that of the CrN coating.The self-corrosion current density of CrAlN coated samples is two orders of magnitude lower than that of CrN coating,and the total polarization resistance Rp of the CrAlN coating is 868.7k?,which is close to 5 times the Rp of the CrN coating.The CrAlN coating exhibits greater corrosion resistance than the CrN coating.When there are large defects in the coating that are artificially manufactured,the corrosive medium is more likely to enter the substrate,and the rate of corrosion is greatly increased.In the neutral salt spray test,after 288h continuous salt spray corrosion,the weight gain per unit rea is only0.1mg for CrAlN coating,which is much smaller than that of CrN coating and Ti-6Al-4V substrate,and the corrosion resistance is obviously improved. |
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