Magnetic Particle Inspection is a non-destructive process used for the detection of surface and near-surface flaws or defects in ferromagnetic (ferrous) materials.
An externally applied magnetic field is directed to the test subject. If the material is without defect, most of the magnetic flux remains below the material’s surface. Magnetic flux is distorted or will leave the part at any flawed area due to interaction with the magnetic field.
The distortion of the magnetic field, depending on the intensity of the magnetism, can extend a good distance through the part and even and into the air. To make this distortion visible, and thus detect any defect, tiny magnetic particles are applied to the surface of the specimen, which are then attracted to the area of flux field leakage, creating a visible indication of the flaw.
The most typical materials used include small iron or iron oxide particles. The particles are typically flowed over the surface using a paraffin or fluid such as water or kerosene. The particles are attracted to the magnetic flux field leakages and thus migrate to and expose defects and flaws.
At Sterling Performance, we employ a strong AC electromagnet which can be used to concentrate the field at the surface where it is needed, making our Magnetic Particle Inspection very robust, even on parts with complex geometry.