| Titanium alloy is an important metal that has been developed in recent ye ars.It has the characteristics of low density,high specific strength,good corrosion resistance,low thermal conductivity,non-toxic,nonmagnetic,good biocompatibility and so on.It is widely used in many fields,such as aerospace applications,marine,biological,and sporting goods.High temperature titanium alloy are mainly used in aero engine blades and other fields to improve the thrust weight ratio and service performance of aircraft.However,when titanium alloy works above 600°C,oxidation will occur rapidly and the part will fail,which seriously limits the application of titanium alloy in high temperature environment.Ti Al intermetallic compounds have the advantages of low density,high elastic modulus,high temperature strength,and good oxidat ion resistance.They have become a wide range of new aerospace materials,but they have poor plasticity at room temperature,and they also have insufficient antioxidant properties at high temperatures,therefore,its application at high temperatures has be en affected.By adding the third element Cr,the activity of Al in the Ti-Al-Cr ternary system can be improved,promoting the formation of Al 2O3,and the oxidation rate of the metal can be significantly reduced.Therefore,the oxidation resistance of the Ti-Al-Cr ternary system is significantly improved and its ultimate temperature is raised.According to the in-situ synthesis reaction of Ti-Al-Cr under the high-energy laser beam,the Ti-Al-Cr high temperature oxidation resistant coatings was prepared on the surface of TC6 titanium alloy by laser cladding technology.The coatings has good macroscopic quality,regular shape and there is no obvious holes and cracks on it.The microstructure of the coating s was observed by OM,the microstructure was observed by SEM,the chemical composition was analyzed by EDS,and the microhardness distribution was tested by a microhardness tester.High-temperature tube furnace was used to test the high-temperature oxidation resistance of the coatings.XRD was used to test the phase composition of the oxide layers,and a series of methods such as OM,SEM and EDS were used to obtain the anti-oxidation mechanism.The elements in the coating are more evenly distributed.A large number of silver-white substances are evenly distribu ted in the coating.It's microhardness is significantly higher than that of the substrate.Up to 1.76 times hardness of the substrate.Cyclic oxidation at 800°C showed that the Ti-Al-Cr coating was significantly enhanced the high temperature oxidation resi stance is about 17 times higher than that of the substrate.The Ti-Al-Cr coating significantly improves the high temperature oxidation resistance of titanium alloy substrates.The mechanism of the high-temperature anti-oxidation performance of the coating is mainly manifested in three aspects.In the first aspect,the coating has good quality and is metallurgically bonded to the titanium alloy substrate,and there are no pores and cracks that become oxygen diffusion channels.The second component is that at high temperatures,the addition of Cr can promote the formation of Al 2O3.At the same time,Cr also oxidizes and generates oxide structure.The two oxide structures are dense and can form a protective oxide film during oxida tion.The third aspect is that the oxide film formed is similar to the thermal expansion coefficient of the coating itself,during the oxidation process no delamination,cracking and spalling occurs like titanium alloy,which effectively isolates the contact between oxygen and non-oxidized parts,reduces their oxidation rate,and significantly improves their high-temperature oxidation resistance. |
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