What role do magnetic particles play in magnetic particle testing?

In magnetic particle testing, magnetic particles are crucial for detecting surface and near-surface discontinuities in ferromagnetic materials. When a magnetic field is applied to the component being tested, any flaws present in the material will disrupt the magnetic field lines. As a result, when magnetic particles are applied to the surface, they tend to cluster at the areas where the magnetic field is distorted due to these imperfections.

This clustering creates a visible indication of the flaws, allowing inspectors to see where potential weaknesses or defects are located. The particles can highlight issues such as cracks, seams, or inclusions, making them invaluable for quality control in critical components. This visual indication is the primary purpose and function of magnetic particles in this testing method, ensuring that any defects can be identified before they lead to failure in service.