What are the two main types of magnetic particles used in MPI?

The two main types of magnetic particles used in Magnetic Particle Inspection (MPI) are categorized as dry and wet magnetic particles.

Dry magnetic particles are typically in the form of powdered particles that are applied to the surface of the test object in a dry form. They are particularly useful for detecting surface and near-surface discontinuities and are often used when high precision is necessary or when working with complex geometries.

Wet magnetic particles, on the other hand, are suspended in a liquid carrier, which allows for better coverage of the test surface. The liquid suspension helps to spread the particles evenly, enhancing their ability to gather at the discontinuities, thus improving sensitivity in detecting flaws.

This distinction between dry and wet particles is crucial in MPI, as the choice of particle type can affect the inspection technique used and the overall effectiveness in revealing defects within the material being examined.