Study on surface stress measurement of laser cladding Fe-based alloy coating based on Rayleigh wave signal analysis

Experimental study on surface stress measurement of laser cladding Fe-based alloy coating based on Rayleigh wave acoustoelastic theory was introduced. Two Rayleigh wave transducers with 5MHz frequency, the distance between which was fixed, were employed to measure the difference in time of flight along the surface of laser cladding Fe-based alloy coating. Rayleigh wave signal responding to different tensile stress was collected and the difference in time of flight between unstressed and each stressed Rayleigh wave signal was calculated with normalized cross correlation function. Results show that the propagation velocity of Rayleigh wave linearly increases with tensile stress increasing, and the maximum difference in time of flight is obtained at tensile stress level of 492MPa, while the relation between tensile stress and the difference in time of flight is obscure with tensile stress further increasing. Furthermore, the thickness of laser cladding Fe-based alloy coating and the deformation of coating surface may result in errors in experiment. Finally the surface stress of laser cladding Fe-based alloy coating is evaluated by Rayleigh wave acoustoelastic technique and the experimental result is well compared with the theoretical value.