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Case Hardening Measurement with Quantitative Surface Acoustic Microscopy



Nelson N. Hsu, D Xiang, Gerald V. Blessing


Case hardening is widely applied to many critical parts in the automotive industry. Determining the hardened case depth is presently a time-consuming destructive process which would greatly benefit from an efficient nondestructive technique. It has been shown that ultrasonic surface-wave measurements are a candidate solution to the problem. However their implementation and acceptance by industry has not taken place due to poor reproducibility and limited accuracy. We have developed an ultrasonic surface-microscopy technique based on a custom-designed broadband, lensless, line-focus PVDF transducer. This technique can be used to accurately measure leaky surface waves of a solid submerged in water, and has been demonstrated in many materials characterization applications. In this paper we apply the technique to measure plasma-nitrided alloy steels. In addition to the group velocity measurements, the phase velocity of leaky surface waves can be determined by straightforward manipulation of the data and subsequent signal processing. Preliminary results about effects of case hardening on elastic wave velocity changes are obtained.
Conference Dates
July 26-30, 1999
Conference Location
Quebec, CA
Conference Title
26th Annual Review of Progress in Quantitative Nondestructive Evaluation


acoustic microscopy, case hardening, depth measurement, surface wave


Hsu, N. , Xiang, D. and Blessing, G. (1999), Case Hardening Measurement with Quantitative Surface Acoustic Microscopy, 26th Annual Review of Progress in Quantitative Nondestructive Evaluation, Quebec, CA (Accessed July 17, 2024)


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Created January 1, 1999, Updated February 19, 2017