Magnetic Particle Testing

Magnetic Particle Testing (MT) is used to detect surface and subsurface in ferroelectric materials such as iron, nickel, cobalt, and some of their alloys. The process puts a magnetic field into the part. The piece can be magnetized by direct or indirect magnetization. Direct magnetization occurs when an electric current is passed through the test object and a magnetic field is formed in the material. Indirect magnetization occurs when no electric current is passed through the test object, but a magnetic field is applied from an outside source. The magnetic lines of force travel perpendicular to the direction of the electric current which may be either alternating current (AC) or some form of direct current (DC) (rectified AC). The presence of a surface or subsurface discontinuity in the material creates magnetic flux leakage. Ferrous iron particles are applied to the part. The particles may be dry or in a wet suspension. If an area of flux leakage is present the particles will be attracted to this area. The particles will build up at the area of leakage and form what is known as an indication. The indication is then evaluated to determine what it is, what may have caused it, and what action should be taken if any. Premier NDT is capable of supplying 1500 to 6000 Amp generators for large applications and Magnetic yokes for smaller applications.