What types of defects can Magnetic Particle Testing detect?

Magnetic Particle Testing (MPT) is specifically designed to detect surface and near-surface discontinuities in ferromagnetic materials. This method involves magnetizing the material and applying a fine ferromagnetic particulate to the surface. The presence of any discontinuities, such as cracks, laps, and seams, disrupts the magnetic field and causes the magnetic particles to cluster at these defects, making them visible under proper lighting conditions.

While this method is effective for identifying surface flaws, it is not capable of detecting internal voids or porosities, as these would not affect the magnetic field on the surface. Similarly, deformation due to thermal processes does not typically create the type of surface indications MPT is designed to reveal. Lastly, microfractures in non-metallic materials would not be detected since MPT is limited to ferromagnetic materials and relies on magnetism, which is a property not applicable to non-metallic substances. Thus, the detection of surface and near-surface discontinuities is the primary benefit of employing Magnetic Particle Testing.