Which non-destructive testing method is used to expose surface and near-surface flaws using a dust of iron particles?

The method that uses a dust of iron particles to expose surface and near-surface flaws is magnetic particle testing. This technique is particularly effective for detecting surface defects in ferromagnetic materials. During the testing process, the component is magnetized, and fine iron particles are applied to its surface. If there are any flaws, such as cracks or voids, the magnetic field will be disrupted, causing the iron particles to accumulate at the flaw sites. This accumulation of particles makes the defects visible under appropriate lighting conditions, allowing for an effective inspection of the material’s integrity.

Other methods mentioned are designed for different purposes. Ultrasonic testing uses high-frequency sound waves to detect internal flaws and does not involve iron particles. X-ray testing utilizes radiation to create images of the internal structure of a material, focusing on internal rather than surface defects. Dye penetrant testing involves applying a liquid dye to the surface, which seeps into flaws and is later revealed using a developer, but it does not use iron particles as part of the inspection process. Thus, the specific application of using iron particles in a magnetic field is what distinguishes magnetic particle testing as the correct choice for identifying surface and near-surface flaws.