Nondestructive Evaluation of Hardened Steel Plates by Ultrasonic Backscatter Technique

In this paper, we use the ultrasonic backscatter technique for measurement of the thickness of the hardened layer (case depth) on inductions-hardened VCN 100 steel plates. The experiment includes an immersion ultrasonic test where both the sample and the ultrasonic probe are immersed in a water tank. The measurement technique is based on the backscattering of ultrasonic waves from the transition zone which lies between the hardened layer and the soft inner core. The backscattered ultrasonic signals are measured and processed by a number of signal processing schemes to extract the thickness of the hardened layer. A scanning system measures the case depth on the surface of the plate samples and produces C-scan images showing the profile of the hardened layer. This technique could be used for nondestructive testing and quality control of hardened specimens.