Nondestructive Evaluation of Coatings

Bulk and Rayleigh (or surface wave) velocities of ultrasonic waves in chromium coatings on steel were measured and an experimental correlation was found between the surface velocity and the hardness. Since qualitative coating evaluation is commonly made using hardnesses as a guideline, the possibility is herewith presented of using the sound velocities of surface ultrasonic waves for this purpose. This provides the advantage of using a nondestructive technique over one that is destructive and more qualitative