MAGNETIC PARTICLE INSPECTION (MT)

Magnetic particle inspection is used for detecting surface and near surface discontinuities in ferromagnetic materials such as iron, nickel, cobalt, and some of their alloys, by applying a magnetic field and magnetic particles to detect of magnetic flux leakage. The magnetic particles are drawn, and held to the surface of the part by the flux leakage which creates a visible indication of any discontinuities.

Advantages

Economical
Simple and fast
Extremely portable
Can even work through thin layers of paint
Large surface areas of complex parts can be inspected rapidly
Best at detecting fine, shallow surface cracks

Limitations

Only ferromagnetic materials can be inspected
Requires relatively smooth surface
Large currents are needed for larger parts
Demagnetization and post cleaning is usually necessary
Only detects surface and near surface discontinuities
Thick paint and or nonmagnetic coverings adversely affect sensitivity