中文摘要：

基于超声波在介质中的传播理论，在当量法基础上采用超声波对激光熔覆层表层裂纹深度进行定量评价。结果表明：表层裂纹信号幅值随裂纹深度的增大而增大，当裂纹深度达到1．0mm时，信号幅值基本保持不变。相同深度表层裂纹超声波信号幅值随检测距离增大而减小，并趋于平缓，分析认为激光熔覆层中各向异性树枝晶组织及层间界面导致声波能量衰减是引起上述结果的主要原因。结合上述研究结果，本研究对激光熔覆层组织引起的声波能量衰减进行补偿，进而实现表层裂纹深度定量评价方法的修正，在一定程度上提高了激光熔覆层表层裂纹深度的评价精度。

英文摘要：

Based on the propagation theory of ultrasonic wave in medium and the equivalent method, quantitative evaluation of surface crack depth in laser cladding coating was studied. The results show that ultrasonic wave signal amplitude of surface crack increases gradually with crack depth increasing. After crack depth attains 1.0 mm, signal amplitude of surface crack nearly keeps stable as crack depth increases further. For the same depth, ultrasonic wave signal amplitude of surface crack decreases gradually as detection distance of ultrasonic wave increases, and signal amplitude tends to be stable further. It is assumed that ultrasonic wave energy attenuation caused by anisetropic microstructure and layer interface of laser cladding coating is the main reason for the above results. In order to improve surface crack depth evaluation accuracy, ultrasonic wave energy attenuation caused by microstructure of laser cladding coating is compensated, and the modified approach for surface crack depth of laser cladding coating is proposed and studied.