Magnetic Particle Inspection

NDT Inspection Method Applicability

The typical use of magnetic particle inspection methods (a.k.a., MPI and MT) are to detect cracks, inclusions, seams, laps, and other discontinuities at or near the surface of ferromagnetic materials. Typical materials that fall into this category include “plain carbon steels” (i.e., ferrite matrix phase – those containing < .8% carbon), low grade stainless steel, cast iron, etc. [Note that a quick and easy test to determine the suitability of MPI is to place a magnet on the part. If the part is not magnetic, MPI is not an applicable test method.]

In general, MPI can be applied at any point during the manufacture and/or in-service use of a ferromagnetic part. MPI cannot be used on non-ferromagnetic materials or on parts with interfering coatings. Surface defects as small as  .015” (.38mm) can be reliably detected with MPI.

 MTC MPI Laboratory Inspection Service

We offer wet fluorescent, continuous and residual, as well as black oxide visible dry powder methods of MPI. The most commonly used MPI method at our facility are wet fluorescent using an oil carrier.

The following are examples of MPI related specifications that MTC is approved to perform:

Shaft MPI rod shot

Shaft MPI rod shot

  • BAC 5424
  • ASTM-E-1444
  • BSS 7040
  • HP6-5
  • MIL-I-6868
  • MIL-STD-1949
  • P3TF9
  • HS 31
  • PN 16.04
  • CMPM
  • MPM
  • RRP 58004
  • SS8805

Common types of parts that MTC MPI processes include gears, splines, gear boxes, liners, shafts, hubs, engine cases, segments, rings, spacers, disks, discs, flanges, rollers, bearings, raceways, housings, links, tubes, forgings, castings, brackets, screws, bolts, washers, nuts, locknuts, etc..

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