Ultrasonic spectroscopy of welded cryogenic materials

The purpose of this paper is to analyze the frequency spectrum of the ultrasonic response of a cryogenic material sample using a nondestructive method. The experimental measurements presented here were obtained by the direct contact method using silicon gel as the coupling medium with the pulse-echo technique, with a 5MHz transducer (Nortec). The instrumentation consisted of an IPR-100 signal generator, an A/D-90 converter and SMC-4 step by step motors from Physical Acoustic Corporation, a sampler and a spectral analyzer. The ultrasonic testing of the welded cryogenic material 10TiNiCr180 was made in the base material (point A1) and in the weld (point A3) without being exposed to a thermal treatment (sample B). After that, the material was exposed to the following thermal treatments: first - welding + hardening (sample 2) and the second welding + hardening + annealing treatment (sample 2p). Because Spectral Peak Ratio was known, it was possible to determine the grain size which was compared with the one obtained by the metallographic analysis. It is noticed a decrease of the grain size after the first thermal treatment (46.5 mu m), but a small increase after the second thermal treatment (48.7 mu m), and we identify some resonance numbers of frequencies 1.46MHz, 2.468MHz, 2.719MHz, using ultrasound spectroscopy obtained by Power Spectral Density.