NDT Methods: Magnetic Particle
Testing consists of magnetization of the article, application of
iron particle, and interpretation of the patterns formed by the
particles as they are attracted by magnetic leakage fields. This
form of testing is usually applied to finished articles, billets,
hot rolled bars, castings and forgings. It can also be used to
check that the processing operations such as heat treat, machining
and grinding did not uncover or cause discontinuities.
Because magnetization of certain metals is possible, small particles that are attracted to magnetic fields are applied to the surface of the test object after or during induction of a magnetic field, thereby detecting certain discontinuities which are present in the material. However, this test method is limited to disclosing only those discontinuities that are at or near the surface.