Non destructive testing (NDT) is the process of inspecting and testing components for discontinuities, or defects without altering or affecting the part in any way, with this when the inspection or test is completed the part can still be used.
Magnetic Particle Inspection:
Magnetic Particle Inspection uses a magnetic field to locate surface and near-surface discontinuities in ferromagnetic materials. When very fine ferromagnetic particles are applied to the surface of the part and the magnetic field encounters a discontinuity the particles will be drawn into the discontinuity, producing a visible indication on the surface of the part.
Florescent Penetrant Inspection:
Florescent Penetrant Inspection uses a very low viscosity fluorescent liquid which is applied to the surface of a part, it penetrates into defects on the surface. Once the excess penetrant is removed, the penetrant trapped in those defects will flow back out, creating an indication which can be seen under black light. Penetrant testing can be performed on magnetic and non-magnetic materials, but does not work well on porous materials.
Nital Etch Inspection:
Nital Etch Inspection is a test to determine if heat has been induced to a hardened steel component by machining, grinding, or other means, which will adversely affect the properties of the component. Under certain circumstances machining and grinding can introduce sufficient heat into a component to “burn” its surface. This is generally caused by local overheating and can produce undesirable changes in the metal’s properties. If an area is overheated, it will appear darker than the surrounding after etching.
