Research On Rare Earth Catalytic Carbonitriding Of TC4 Titanium Alloy By LPES Method

Titanium alloys have important applications in the aerospace industry owing to their high specific strength and excellent corrosion resistance.However,the low hardness and adhesion wear of titanium alloys restrict its application as a transmission part in the aerospace industry.To prepare a carbonitriding layer on the surface of titanium alloy by carbonitriding surface treatment technology is an effective way to solve the problem.As an emerging surface treatment technology,liquid plasma electrolytic saturation?LPES?has the advantages of high processing efficiency,simple process and wide application range.In this thesis,rare earth catalytic carbonitriding treatment was carried out on the surface of TC4 titanium alloy simply and efficiently by LPES.The principle and process of rare earth catalytic carbonitriding were studied to provide technical foundation for promoting the application of titanium alloy transmission parts.The main research work and achievements completed in this thesis are as follows:1.The temperature in the LPES system was studied by theoretical calculation,simulation analysis as well as experiment.The calculated values,simulated values and measured values of the workpieces surface and center temperature show that the input voltage is the key factor affecting the temperature of the system.The results of the system temperature have guiding significance for the selection of the processing voltage.2.The atomic diffusion model of carbonitriding by LPES was established.The change of atomic concentration in the layer was studied.The results show that atomic surface concentration,diffusion time,diffusion temperature and diffusion activation energy are the key factors affecting the atomic concentration in the layer.The effect of rare earth oxide CeO₂ in the carbonitriding by LPES was studied experimentally.It was found that the introduction of CeO₂ effectively increases the atomic surface concentration,reduces the diffusion activation energy,promotes the diffusion of carbon and nitrogen atoms,and has a good catalytic effect on the carbonitriding by LPES.3..The process of carbonitriding by LPES was studied.The surface morphology,cross-section structure,element distribution,hardness and wear resistance of the layer were analyzed.The effect of voltage and time on the strengthening layer was studied.The results show that the surface hardness of the strengthened layer treated with CeO₂ at 320V for 30min reaches 987HV0.01,and the surface wear resistance of TC4 titanium alloy after strengthening is significantly improved.