中文摘要：

基于当量法缺陷评价理论，结合激光熔覆层组织引起的超声波衰减理论分析，对激光熔覆层中缺陷进行了无损评价。采用中心频率为2．5MHz的纵波对直径不同的预置通孔缺陷进行检测。结果表明，缺陷位置不同时，缺陷尺寸与缺陷回波信号幅值间关系基本相同；激光熔覆层组织中界面是引起声波能量衰减的主要因素。在熔覆层底面回波试验结果基础上，提出了对当量法评价激光熔覆层中缺陷尺寸进行修正的方法，即D’=B（1＋α）D/A.验证试验表明采用该方法可显著提高激光熔覆层中缺陷尺寸评价精度。

英文摘要：

The flaws in the clad coating were nondestructively evaluated based on the theory of equivalent method for flaws evaluation and the theoretical analysis of ultrasonic energy decline in coating. The longitudinal wave with 2.5 MHz frequency was employed to obtain the echo signals of preset through hole flaws with various diameter. The results show that with the variation in flaws position within the laser clad coating, the relationship between the flaw size and the amplitude of echo signal almost keeps unchanged. The interface among the microstructure of laser clad coating is the dominant influencing factor for the energy attenuation of ultrasonic. In addition, the compensation formula for the flaw evaluation of coating is proposed based on the analysis of bottom echo signal of coating, i. e.D＇=B（1＋α）D/A~ The proof