Numerical Simulation And Experimental Study On Thermodynamic Coupling Process Of High Speed Cladding

High-speed laser cladding technology has high cladding efficiency,flat coating surface and high bond strength.It solves the problem of low efficiency of traditional melt coating preparation.It plays a huge role in the surface repair of automotive engines,transmissions,turbine blades and hydraulic cylinders and other components.The temperature field distribution,thermal cycling characteristics,transient thermal stress distribution and residual stress generation mechanism of the high-speed cladding process are more complex than those of the conventional cladding process.The transient temperatures and stresses during highspeed cladding are difficult to capture completely by experimental methods.It directly affects the effective control of defects such as porosity,microcracks and residual stress in the coating during the preparation of high-speed thin coatings.In response to the above problems,relevant research was carried out under the support of a special research project of the Shaanxi Provincial Department of Education.The main work is as follows:(1)A finite element model of a thin coating with a semi-elliptical cross-section was created using the ANSYS APDL program.The analytical model was divided into full hexahedral cells by introducing an adaptive mesh virtual planning algorithm.A new composite heat source model was proposed.The transient temperature field of the high-speed cladding process was simulated.The effect of transient temperature on melt pool morphology during the cladding process was investigated.The thermal cycling characteristics of the coating surface,the depth of the melt pool and the bonding surface between the coating and the substrate were also analyzed.Finally,the melt temperature field and thermal cycle characteristics were examined and verified by infrared thermal imaging experiments.(2)Thermodynamic coupled field program model was adopted.Transient thermal stresses and thermogenic residual stresses in high-speed laser cladding processes were simulated.The law of transient thermal stress change and transient equivalent deformation of thin coatings during the melting process were studied.Then,the path of the residual stress measurement point of the high-speed fused thin coating was planned.The residual stress distribution pattern of cooled thin coatings after cladding was explored.The effect of process speed on the residual stresses in thin coatings was also analyzed.(3)The blind hole method residual stress experimental testing system was built and the measured residual stress values were obtained.Experimental test results were utilized to validate the numerical simulation results of high speed cladding residual stress fields.The residual stress distribution patterns along the scanning direction and the vertical coating direction under the high-speed cladding process were also analyzed.The residual stress distribution patterns along the scanning direction and perpendicular to the coating direction were also analyzed for the high-speed cladding process.The effect of the two different processes on the residual stresses in thin coatings was investigated in conventional and high speed cladding.Reliable theoretical support was provided to further solve the problem of residual stresses in thin coatings by high-speed laser cladding.