Numerical Simulation And Experimental Research Of IN718 Coating Fabricated By Ultrasonic Vibration-assisted Laser Cladding

The rapid development of important industries such as aerospace,rail transport,and shipping has placed stringent demands on the manufacturing performance of key metal components.As one of the basic technologies for high-end smart manufacturing and remanufacturing,laser cladding improves the parts performance by melting metal powder on the substrate surface and preparing a coating with excellent properties.However,both the current characteristics of the process and materials result in coatings that are prone to defects such as coarse organization,porosity,and cracking,and these problems present a serious obstacle to the widespread dissemination of the technology.This paper presents research related to the ultrasonic vibration-assisted laser cladding process with IN718 alloy as the research object.Based on theoretical analysis,numerical simulations are used to support experimental investigations.The melt pool heat mass transfer process and the main mechanisms of ultrasonic vibrations in the melt pool are analyzed.The mechanism of ultrasonic vibration in terms of tissue refinement and property improvement is explored.The main research contents are as follows:(1)A finite element model of the laser cladding process was developed.Based on the analysis of the interaction between the laser beam and the powder flow,the numerical analysis model of laser cladding of IN718 was established with the knowledge of heat transfer and fluid dynamics.The heat transfer with phase change process,the melt pool convection behavior,the evolution of the coating morphology,and the distribution of solidification characteristics parameters on solid-liquid front are analyzed.It provides theoretical and technical support to further explore the effect of ultrasonic vibration on the heat and mass transfer process of the molten pool and its solidification microstructure.(2)Ultrasonic vibration-assisted laser cladding coating mechanisms and methods are explored.The ultrasonic cavitation and acoustic streaming effects produced by ultrasonic vibrations in a liquid molten pool are systematically analyzed.The effect of ultrasonic parameters on the cavitation process of the melt pool is discussed by solving the R-P equation.Using fluid dynamics and pressure acoustics as theoretical support,a numerical model of acoustic streaming in the molten pool is developed to investigate the effect of ultrasonic vibration on the heat and mass transfer process,laying a theoretical foundation for the analysis of the mechanism of microstructure evolution and performance enhancement.(3)Single and multi-pass laser cladding experiments were carried out to analyze the effect of ultrasonic vibration on microstructure and performance of coatings.The longitudinal high-frequency vibration from the bottom of the substrate was introduced into the melt pool.Based on the previous researches,optimal process parameters and experimental protocols were selected to carry out a series of experiments with and without energy field-assisted laser cladding of IN718 coatings.Characterization of the microstructure,phases,and properties of IN718 coated specimens were made using Scanning Electron Microscope(SEM),X-ray diffraction(XRD),and other testing methods.The effect of ultrasonic vibration on the melt pool heat transfer and solidification and crystallization processes is combined to reveal the mechanism of ultrasonic vibration on the grains refinement and the improvement of the properties(micro-hardness and wear resistance).