Non-Destructive Testing applications have broad usage area from the medical to heavy industries. Several advanced methods, mainly developed from the conventional methods, are used to render the technique more flexible and easier to interpret. Ultrasonic Phased array technology is one of them which can be employed in almost any test, where conventional Ultrasonic Testing (UT) has traditionally been used. Weld inspection, flaw detection and the wall thickness determination in corrosion surveys are the most important applications. The benefits of Phased Array technology over conventional UT come from its ability to use multiple elements to steer, focus and scan beams with a single transducer assembly. In this study, the advantages and limitations of the Phased Array system were investigated via using special test blocks of St37 and SAE 4140 (42CrMo4) steels having well-defined artificial defects. The reliabilities of the Phased Array and conventional Ultrasonic Testing methods were compared using a statistical approach, the Probability of Detection
