Flaw Inspections

A flaw or defect is a discontinuity within a material, and it can have various causes. Flaws may be inherent, occur during casting, arise during heat treatment or hot working processes, or result from mechanical fatigue, such as fatigue cracks.

A discontinuity is an interruption in the material’s physical structure, but it does not necessarily affect the usability of the component. The usability can only be determined after evaluating the defect and applying specific acceptance criteria. Defects can take various forms, such as cracks, porosity, inclusions, crystallizations, splits, segregations, or cavities.

Several methods can be used to evaluate flaws. One common approach is penetrant testing, which involves applying a highly capillary liquid to detect surface flaws. A developer liquid is then applied to create a contrast, making the defects visible.

Another method is magnetic particle testing, which uses a magnetic field to identify surface or near-surface flaws. A liquid containing magnetic particles is applied, and defects like cracks interrupt the magnetic field in the component, causing the particles to cluster at the discontinuity. This technique is particularly useful for inspecting welds and castings and can detect flaws as small as a few millimeters.

Porosity detectors are also used for non-destructive testing to locate and identify porosity, exposed areas, or thin spots in protective coatings. These coatings are often applied to metals and conductive surfaces for corrosion protection.