Stress Measurement of Laser Cladding Remanufacturing Coating with Ultrasonic Nondestructive Evaluation

Based on acoustoelastic theory, stress measurement of laser cladding coating with Rayleigh wave was investigated.The acoustoelastic formula for evaluation of stress in laser cladding coating was simplified by means of Taylor series expansion method.Combined with the static load tensile test, acoustoelastic coefficients were determined.The results show that the variation rate of Rayleigh wave signal velocity in Fe314 alloy coating increases linearly with the increase of stress.When tensile stress is greater than 495MPa, the variation rate of Rayleigh wave signal velocity does not change linearly any more.Based on the analysis of ultrasonic propagation theory and microstructure of laser cladding coating, the changing rule of acoustoelastic curve and its influence mechanism on stress measurement were analyzed, the inhomogeneous deformation of anisotropic laser cladding coating is the main cause of the "wave-type" fluctuation of acoustoelastic curve in high stress stage.Results show that anisotropic tissue effect can affect the result of stress measurement;the penetration in laser cladding layers can be ignored. By fitting the acoustoelastic curve, anisotropic tissue effect factor is determined.The experimental results show the maximum relative error in stress measurement is 4.4%, the method can realize the nondestructive evaluation of the stress in laser cladding coating.