Microstructure And Properties Of Laser-plasma Composite Thermal Barrier Coatings

With the continuous progress of modern technology and industry,and the continuous development of engineering power machinery manufacturing technology,the working environment of its equipment is becoming more and more severe,the parts of the equipment which work in high temperature environment are subject to excessive thermal loads during operation.Now researchers have proposed the use of thermal spray technology to prepare ceramic thermal barrier coatings to reduce surface temperature of component.However,due to the characteristics of the thermal spraying process,the prepared thermal barrier coating has a typical layered structure,and there are defects such as pores and cracks in the coating.In addition,the main combination of the coating and the substrate is mechanical riveting,which makes the thermal barrier coating prepared by the thermal spraying process has a lower bonding force with the substrate and is easy to peel in a high heat load environment.Aiming at how to solve the internal defects of the thermal barrier coating and prolong the working life of the thermal barrier coating,it is proposed to use laser remelting technology to perform a second heat treatment on the plasma spray coating to improve the various defects of the coating after spraying and increase the coating use performance.The laser remelting process can better suppress most of the defects such as cracks and gaps in the coating.After remelting,the coating density increases,the bonding strength with the substrate increases,and the overall performance of the coating is also improved.Therefore,it is of great significance to study the structure and properties of laser remelting coatings.This article first conducts basic research on the morphology,element distribution,phase structure,and microhardness of supersonic plasma spray coatings.Thermal shock experiments were performed to analyze the thermal shock failure mechanism of the plasma spray coating,which laid a theoretical foundation for subsequent laser remelting experiments.Secondly,the morphology of the laser remelted coating prepared under different process parameters was analyzed,and the influence of laser power and laser scanning speed on the coating structure was studied.The experimental results show that the coating material is more sensitive to the choice of laser power.Excessive power can easily cause the coating material to vaporize and even peel off from the surface of the substrate.The laser remelting coating surface formed grid-like cracks.As the laser scanning speed decreased,the diameter of the network cracks on the coating surface gradually increased and pores appeared on the surface.Finally,the laser remelting coating with good molding quality is selected to study the coating's microstructure,element distribution,phase structure,and microhardness,and perform thermal shock experiments on it to observe the failure process of the laser remelting coating.,Analyze its failure mechanism.The experimental results show that the laser remelting treatment changes the layered structure in the original plasma spray coating,eliminates defects such as pores,cracks and unmelted particles in the coating,and also has better thermal shock performance than the plasma spray coating.