Particulate Metal Composites as Backing for Ultrasonic Transducers for Continuous Nondestructive Measurements at Moderate and High Temperatures

Abstract

There is an increasing need for ultrasonic transducers able to operate continuously at high temperatures in many industrial sectors. Operating temperatures may be 600 °C and higher. There is not any commercial solution to deal with such applications, and only a few ultrasonic prototype probes exist. It is, therefore, important to find new materials suitable for the manufacture of higherature ultrasonic probes. One important element of ultrasonic probes is the backing as it enables the control of both sensitivity and bandwidth. The goal of this article is to explore the possibility of using particulate metal composite as a higherature backing elements. Several tin-tungsten composites with different tungsten volume fractions were produced by uniaxial pressing. The backings were characterized by ultrasonic spectroscopy. The backings have an impedance ranging from 25 to 31 MRayl with attenuation at least equal to 20 dB/cm and up to 191 dB/cm. In order to operate at 600 °C, a sample of Al/W composite was produced. Its impedance ranged from 8 to 10 MRayl with a mean attenuation of around 156 dB/cm at 4.5 MHz. The metallic composites, therefore, have ultrasonic properties suitable for use as backing. Moreover, they are relatively easy to manufacture. These are, therefore, very interesting materials for higherature ultrasonic probe applications.