激光熔覆涂层弹性模量的激光超声表征方法

Characterization of Elastic Modulus of Laser Cladding Coatings Using Laser Ultrasonic Method

为了表征激光熔覆涂层的弹性模量,提出了一种基于激光超声表面波技术的无损表征方法。首先,建立了表面波在涂层-基体两层结构中传播的理论模型,通过理论求解表面波的波动方程,得到了带涂层结构的表面波理论频散曲线。其次,通过激光超声设备在激光熔覆涂层不同区域采集表面波信号,并利用二维傅里叶变换得到了表面波的实验频散曲线。为了求解表面波传播的逆问题,得到涂层的弹性模量,采用非线性回归方法,通过最小化实验频散曲线与理论频散曲线之间的差异,确定了涂层不同区域的弹性模量。根据涂层上不同区域弹性模量的差异,可反映出激光熔覆涂层组织的不均匀性。利用激光超声表面波技术评价激光熔覆涂层的弹性模量,具有一定的工程应用价值,可为改善激光熔覆工艺提供技术保障。

To characterize the elastic modulus of laser cladding coating,a nondestructive evaluation method based on laser ultrasonic surface wave is proposed.First,we establish a theoretical model of surface wave propagation in two-layer structures,namely,the coating and substrate.Then,we obtain the theoretical dispersion curves by solving the wave equation.Afterward,we excite and receive the surface wave signals on different areas of the laser cladding coating using laser ultrasonic equipment and obtain the experimental dispersion curves of the surface wave using two-dimensional Fourier transform.To solve the inverse problem of the surface wave,the elastic modulus of different coating regions is determined by minimizing the difference between theoretical and experimental dispersion curves.According to the elastic modulus on different areas of coating,we conclude that the coating material prepared using laser cladding technology is nonuniform.The laser ultrasonic surface wave method is useful for testing the elastic modulus of laser cladding coating and improving the laser cladding technology.