Arc Ion Plating-nitride Coatings For Titanium Alloys

Ti alloy has a higher specific strength. If Ti-Ni high temperature alloy is applied to the components and parts of the aircraft engine, such as compressor set and blade, the mass of the engine will lighten and thrust-weight ratio will increase. However, Ti alloy has some problems including bad abrasive resistance, adhering attrition, oxide etch at high temperature, and dissolved oxygen to brittle. In this work, Arc ion plating technology was used to deposit three types of coatings including Tio.7Alo.3N/TiN (inside:Tio.7Alo.3N, outside:TiN), Ti0.49Al0.49Y0.02N/TiN (inside:TiN, outside:Ti0.49Al0.49Y0.02N), Ti0.48Al0.48Y0.04N/TiN (inside: TiN, outside:Ti0.48Al0.48Y0.04N) on the substrate of TA11alloy. The performances of these coatings were investigated, such as hardness, abrasive resistance, scour resistance, thermal shock resistance, thermal fatigue resistance, constant temperature oxidation resistance, and the corrosion resistance in sodium chloride salt film and water at400℃.The average micro hardness of the TA11alloy is about HV300. Tio.7Alo.3N/TiN, Ti0.49Al0.49Y0.02N/TiN, and Ti0.48Al0.48Y0.04N/TiN can significntly increase the hardness of the TA11alloy, which is HV1900, HV3000and HV5150, respectively. The hardness is one of the important factors to affect the abrasive resistance and the sand erosion resistance. The addition of AI and Y can improve the hardness of the coating.The abrasive resistance and the scour resistance quality evaluation of coating samples is that the Ti0.48Al0.48Y0.04N/TiN layer is better than the Tio.49Al0.49Y0.02N/TiN layer which is better than the Tio.7Alo.3N/TiN layer.When the airplanes sever in the marine environment, the engines face to the problem of water vapor and solid NaCl which can make the corrosion of Ti alloy parts fast. Because of the combined action of Cl and O, water vapor promotes to create the intermediate product HCl(g) under the mechanism of "Activation Oxidation" corrosion. Moreover, HCl(g) will repeat to react with the base material so that the catalytic corrosion processes will be accelerated. After preoxidation processing, each of Tio.7Al0.3N/TiN, Tio.49Al0.49Yo.02N/TiN, and Ti0.48Al0.48Y0.04N/TiN layers can significantly improve the corrosion resistance of TA11material in sodium chloride salt film and water vapor. Volatile chloride can be prevented to produce and spread into the matrix. At the severing temperature of400℃, the TA11alloy matrix can be protected well. At the same time, the thermal shock resistance, thermal fatigue resistance, isothermal oxidation resistances are good for application so that safe reliability can be trusted. Moreover, Y element can also improve the oxidation resistance and corrosion resistance of the layers.