Is it possible to check the sigma & intermetallic phases in super-duplex tubes using online ultrasonic testing equipment and if yes what is the minimum requirement for the testing machines?
Ferrite meters such as Diverse MF300F, Feritscope MP30, can be calibrated (with a lot of effort) to coarsely quantify sigma phase and other intermetallics. Calibration involves replicas and sectioning. Unfortunately, the meters will only assess to around 3 mm depth.