Experiment On Laser Engineered Net Shaping Of Inconel718/NiCrAlY/ZrO₂ Functional Graded Material

Superalloy Inconel718 has excellent high temperature properties,and is extensively used in the manufacturing of high temperature parts.However,with the development of high temperature equipments,the working temperature has been higher than the limit of superalloy.Preparing thermal barrier material on the outlayer of superalloy can effectively enhance the thermal properties of the parts,and can increase the lifespan,further to promote the development of high temperature equipment towarding higher performance and efficiency.Ni Cr Al Y/Zr O2 is the most widely used combination of thermal barrier materials in industrial production.Zr O2 ceramic has excellent high temperature resistance,low thermal conductivity,high hardness and wear resistance,thus it can provide excellent thermal protection.Ni Cr Al Y also has certain anti-oxidation capabilities and is often used as a bonding metal layer to connect high-temperature alloy and ceramic surface layer.However,due to the difference of thermal expansion coefficient between different kinds of materials,the temperature and stress load in the working environment of high-temperature components frequently change,and thermal barrier materials often suffer spalling failure,which results in damage of high-temperature components.The graded thermal barrier material prepared by the laser engineered net shaping technology can gradually change the composition and properties of the material in one direction,reduce the interface mismatch problem,and at the same time,the formed material has a dense microstructure and a strong bonding force.In this thesis,the composite materials and functionally graded materials were prepared by the laser engineered net shaping technology.The reasonable processing parameters were determined and the microstructure and mechanical properties were tested.The changing patterns of the microstructure of different composition composite material,as well as the transforming mechanism of the mechanical properties of different composites were achieved,which has a guiding significance for the design of the transitional plan of functionally graded materials.The test results of the functionally graded material verify the reliability of the graded material combination and the feasibility of laser engineered net shaping preparation.The specific research contents are as follows:(1)Inconel718,Ni Cr Al Y,and Zr O2 materials were used,and the forming experiments of Inconel718/Ni Cr Al Y and Ni Cr Al Y/Zr O2 composites with different composition ratios were carried out to optimize the process of forming the block composites and to obtain composite samples with good morphology.The microstructure,phase composition,and element distribution of different composition composites were examined to further analyze the mechanism of the formation of the structure,the precipitation behavior,and the changing patterns of grain morphology.(2)The microhardness,friction and wear properties of composite samples with different composition ratios were measured.Based on the microstructure,phase composition,and precipitation behavior,and the mechanical properties changing laws were summarized.The transitional plan of functionally graded materials was designed according to the changing law of composite materials and properties.(3)A functionally graded material block was prepared according to composites forming process.The research observed the longitudinal section of the graded material,analyzed the transition of the microstructure,and compared its microstructure with the microstructure of the composite,figured out the effect of the graded material structure on the microstructure.Analyze the variation of each element along the direction of the gradient,and a comprehensive evaluation of the transition of the graded material was performed.