Study On Process And Properties Of NiCrAlY/Al₂O₃ Functionally Graded Materials Via Direct Laser Deposition

Nickel-based alloy is an excellent high-temperature material that maintains excellent overall performance at medium and high temperatures.However,with the rapid development of aerospace technology and energy technology,the service temperature is also higher and higher,exceeding the nickel-based alloy.The normal service temperature is also diversified.At present,the preparation of coating materials on the surface of components is the most effective method,which can greatly improve the high temperature resistance,wear resistance and corrosion resistance of the components,and can be adapted to diversified use requirements.As a coated high-temperature protective coating,the thermal barrier coating is the fourth-generation high-temperature protective coating.The surface layer is a ceramic layer with a bonding layer in the middle and a high-temperature alloy at the bottom,which can effectively resist heat and corrosion.Role,widely used in aerospace energy and other fields.NiCrAlY coating has both high temperature oxidation resistance and hot corrosion resistance,as well as good toughness and fatigue resistance.It can be used as a bonding layer in thermal barrier coatings or as a stand-alone product.Al₂O₃ ceramics have excellent resistance to high temperature oxidation,high hardness and wear resistance,and are excellent high temperature resistant materials.However,due to the difference in thermal expansion coefficient between the metal and the ceramic,the surface ceramic layer peels off from the one under the action of temperature and load cycle,thereby causing the coating to fail.The form of the functional gradient can make the material composition gradually transition,reduce the interface effect,and alleviate the stress concentration.The functional gradient material is prepared by direct laser deposition technology,and the structure is dense and the bonding force is strong.This research is mainly to study the formation of NiCrAlY/Al₂O₃ functionally graded materials by direct laser deposition.The process parameters（single pass single layer test,single pass multilayer test and multi-channel multi-layer experiment）were used to optimize the process parameters,and the NiCrAlY/Al₂O₃ composites with different composition ratios were formed,and the microstructure analysis and mechanical properties were tested.The results of the material forming experiment select the gradient path and shape the functionally graded material,and perform microstructure inspection and mechanical property analysis on the shaped gradient part.The main contents of this research are as follows:（1）Experimental study on the composition of NiCrAlY/Al₂O₃ composites with different composition ratios.Single-layer single-layer experiments,single-channel multi-layer thin-wall forming experiments and multi-layer multi-layer block forming experiments were carried out to explore the influence of process parameters（laser power,powder feeding rate,scanning speed,etc.）on the formed samples.Different composition composite materials and suitable forming parameters of different structures make the sample forming morphology better.（2）Phase composition,microstructure and element distribution of different proportions of NiCrAlY/Al₂O₃ composites formed in the process experiment.Analysis of the differences between the phase,microstructure and elemental distribution of the same piece provides a theoretical basis for the subsequent mechanical properties testing.（3）The mechanical properties of different proportions of NiCrAlY/Al₂O₃ composites formed in the process experiment were tested.Evaluate the properties of materials with different compositions,including hardness testing,friction and wear testing,and corrosion resistance testing,combined with microscopic analysis.（4）According to the basis of the composite forming experiment,the appropriate components are selected for the gradient material forming.The microstructure and element distribution were detected for the shaped gradient samples,and the microhardness test was performed.