Nondestructive measurement of coating thickness using through thickness ultrasonic velocity measurements

A new methodology has been developed for online measurement of coating thickness using ultrasonic velocity measurements. This method is based on the change in through thickness ultrasonic velocity in the coated specimen with change in the coating thickness when a difference exists between the ultrasonic velocities in the coating and the substrate. This methodology has been demonstrated for the determination of the thickness of NiAl coating on a high temperature nickel chromium alloy substrate with an accuracy of ± 10 µm (±4 x 10-4 in)