Abstract
An ultrasonic non-destructive testing has found out a new phenomenon in several stamped forgings made from heat-resistant nickel alloys (Ni-superalloys) of two grades: local attenuation of the bottom echo signal amplitude, when the workpiece surface had large (over 20 mm) randomly located zones with significant (up to 1.5%) fluctuations of the longitudinal ultrasonic wave propagation velocity. On top of that, there were no various grain sizes or coarse-grained structures that usually lead to a an increase of a rate of ultrasonic attenuation in such alloys, and which triggers off a bottom echo signal amplitude attenuation. The Article states the studies carried out to explain the tangible reasons of the detected macroinhomogeneity of the velocity, and how it associated with a bottom signal amplitude attenuation.
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