What are the two types of indicating mediums used in magnetic particle inspection?

In magnetic particle inspection (MPI), the two types of indicating mediums are classified as wet and dry process materials. The wet process utilizes a suspension of magnetic particles in a liquid medium, often water or oil, which allows for easy application and provides better coverage over the surface being inspected. This method can more effectively detect surface and near-surface discontinuities, as the liquid helps to draw the particles into any flaws.

The dry process, on the other hand, uses dry magnetic powder that can be applied to the surface. It is typically used when a cleaner environment is needed or when the component in question cannot tolerate liquids. This method is effective for certain applications where a quick inspection is necessary, and it's easier to clean up after the inspection is complete.

These two methods both serve the function of highlighting areas of magnetic disturbance, which indicate potential flaws in materials, thereby helping to ensure the integrity of components in various industrial settings.