Non-destructive testing and acoustic microscopy of diffusion bonds

Despite successful applications of diffusion bonding, there is a lack of good quality assessment methods. A survey of published results shows non-destructive testing techniques (NDT) developed for fusion welds to be ineffective in indentifying the much smaller defects found in diffusion bonds. An investigation into the possibilities of using electrical resistance measurements for NDT shows the requirement of equipment with a very high stability and sensitivity. Finally the use of very high frequency ultrasonic sound in an acoustic microscope is considered as a method of defect investigations. This acoustic microscopy proved to be a highly encouraging new line of investigation for the examination of diffusion bonds.