An improved methodology for the inspection of titanium alloys

In an effort to improve the detection of low-reflectivity flaws in large-grained alloys such as titanium, General Electric has developed and implemented a high sensitivity ultrasonic inspection method. This method involves the use of multiple, subsurface-focused sound beams in combination with digital C-scan image acquisition and display, and signal-to-noise ratio based flaw detection. It is derived from the principle that the signal-to-noise ratio of flaw echoes is improved by limiting the volume of material interacting with the ultrasonic pulse at any given point in time. It is possible to measure and control this volume using knowledge of the beam geometry and frequency spectrum. Fundamental data has been collected which demonstrates the improvement in the detection of low reflectivity inclusions, such as titanium hard-alpha, provided by limiting the ultrasonic pulse volume. An inspection system for titanium billet based on this approach has been in production use for over three years and is providing improved inspection sensitivity.