Study On Preparation And Corrosion Properties Of Multi-element Nitride-based Composite Coatings

Titanium alloys have been widely used in aero-engine compressor blades because of its good mechanical properties and corrosion resistance.When the aircraft is flying at low altitude or the carrier-based aircraft is parked,the blades will be affected by various complex environmental factors and may fail or even fail.Long-term service in high-temperature,high-humidity,high-salt and stress marine environments causes severe corrosion of aeroengine compressor blades,resulting in huge losses.In recent years,metal nitride coatings have been widely used on alloy surfaces,showing significant advantages in improving the thermal stability,oxidation resistance,and corrosion resistance of substrates.At present,there are many studies on the hot salt corrosion performance of metal nitride coatings on titanium alloy surfaces,but the hot corrosion mechanism of metal nitride coatings under external stress is still unclear.Therefore,it is of great significance to study the hot-salt corrosion performance of metal nitride protective coatings on titanium alloy surfaces under external stress.In this study,Ti Al N/Cr,Ti Al N/Cr N,and Ti Al N/Cr Al N(5/10)and Ti Al Ta N/Cr Al N(5/10)multicomponent nitride-based composite coatings with different modulation periods were prepared on the surface of titanium alloys by multi-arc ion plating technology.The corrosion behavior and corrosion resistance mechanism of different coatings at 500 °C were studied by constant temperature oxidation test,hot salt corrosion and hot salt stress coupled corrosion tests.The main results are as follows:(1)In Ti Al N/Cr coating,Ti Al N/Cr N coating,Ti Al N/Cr Al N coating with 5 modulation periods(abbreviated as Ti Al N/Cr Al N-5)and 10 modulation periods Ti Al N/Cr Al N(abbreviated as Ti Al N/Cr Al N-10)among the four coatings,the oxidation process of the coating can be slowed down and the high temperature oxidation resistance of the coating can be improved by optimizing the composition of the interlayer and increasing the modulation period.The hot salt corrosion test results show that the Ti Al N/Cr Al N-10 coating exhibit better resistance to hot salt corrosion resistance.In the hot salt stress corrosion test,the action of external stress accelerated the destruction and corrosion failure of all coatings.However,compared with Ti Al N/Cr and Ti Al N/Cr N coatings,Ti Al N/Cr Al N-5 coatings and Ti Al Ta N/Cr Al N-10 coatings showed better thermal salt corrosion resistance.The main reason is that the addition of Al element can improve the toughness of the intermediate layer and increase the number of modulation period layers,which can improve the structural compactness of the multilayer coating,reduce the formation of penetrating defects,and improve the stress corrosion resistance of the coating.(2)The composition of the Ti Al N top layer of the multilayer coating is optimized.Ti Al Ta N/Cr Al N-5 and Ti Al Ta N/Cr Al N-10 multilayer coatings with different modulation periods were obtained and compared with Ti Al Ta N monolayer coating.The hot salt corrosion results show that the Ti Al Ta N single layer coating has obvious corrosion cracking under the external stress load,while the multilayer coatings still have good resistance to hot salt corrosion cracking resistance under high stress.In particular,the Ti Al Ta N/Cr Al N-10 multilayer coating not only has good hot salt corrosion resistance,but also shows good crack propagation resistance under stress loading,indicating that the increase of the modulation period improves the barrier ability of the coating to oxygen or corrosion medium.This is mainly because the high interface density can greatly reduce the internal defects and cracks of the coating,restrain the internal crack propagation of the coating,and reduce the propagation or diffusion path of the corrosion medium.In addition,the interfacial structure space of the multi-layer coating can allow the release of internal residual stress and reduce the volume mismatch of the corrosion products of the coating,thus improving the hot salt stress corrosion resistance of the coating.