Magnetic Particle Inspection

Magnetism (Magnetism) is the ability of one substance to attract (or repel) another magnetizable substance. This ability was first discovered in ancient Greece in a mineral later called "Magnetite". Later, famous physicists such as Bergmann, Becquerel and Faraday discovered all other materials with magnetic ability.

 

Today, Inspection with Magnetic Particles is widely used to determine the Surface and Subsurface discontinuities of ferromagnetic materials (Iron, Nickel and Cobalt).

The magnetic particle test is applied to materials that can be easily magnetized. This method is used to detect subsurface discontinuities that are open to and close to the surface. For this, the test piece is first magnetized by passing a permanent magnet, electro-magnet or electric current through or around the test piece. Thus, magnetic lines of force are formed in the material. In case of any discontinuity crossing these lines, the lines of force continue on their way by jumping over the discontinuity, so an intense stray magnetic field is formed on the discontinuity. Fine iron powders are sprinkled on the test surface to make the discontinuity visible. The dense leakage area collects the iron powders on the discontinuity, making the discontinuity visible. Thus, the location, shape and size of the discontinuity are determined.

 

Magnetic Particle inspection is frequently used in forging, casting, welded fabrications, machining parts, machine elements, turbine blades, pressure vessels, post-heat treatment, post-grinding or post-service periodic controls of working parts. The technique, place, time and quality levels to be applied are decided by our Level-3 specialist in line with customer demands.

Advantages...

 

  • Best method for detecting fine and shallow surface cracks in ferromagnetic materials.
  • A fast and relatively simple NDT method.
  • Generally cheap.
  • It can also be worked in the presence of thin layers of paint.
  • It has little restriction in terms of size and shape of the test piece.
  • It's a very portable method.

Disadvantages...

 

  • The material must be ferromagnetic. (Iron, Nickel, Cobalt)
  • The direction and strength of the magnetic field are important.
  • It can only detect surface and near-surface discontinuities.
  • Sometimes it requires high current.
  • There is a possibility of burning the test piece.
  • The part should usually be demagnetized. And that can be difficult.