Destructive tests are applied to sample lots where testing specific features of parts is enough to prove conformity. This type of test “slices and dices” a part to gather information for the specific feature but renders the part unusable.
Non-destructive testing (NDT) methods “look into” a cast part to find discontinuities and differences in material characteristics that could lead to part failure. Non-destructive methods test every part in a lot to assure that the parts are sound and usable after the inspection.
The NDT lab at Kovatch Castings provides the following in-house NDT testing methods for our cast parts.
Sometimes called “mag particle,” magnetic particle testing is a process that reveals cracks and similar defects on, or just below, the surface of the casting to about 1/16″ deep. In short, the metal piece, generally steel, is placed in a magnetic field, polarizing each end of the part, creating a north-south pole magnet. If there is a crack in the surface, additional north-south poles are created at the actual crack. This area is known as “magnetic flux leakage” due to the break in the overall magnetization of the part. When a wet suspension of magnetic particles is applied to the part, they are attracted to the cracks and are visibly apparent.
Liquid penetrant testing is a process that uses the application of a fluorescent solution to the part and allowed to soak into any voids or fissures in the part. After the excess solution is removed, the part is then given a light coat of developer. It is then examined using an ultraviolet light source (or “blacklight”) to expose any voids or cracks in the surface of the part. Liquid penetrant testing can be performed on magnetic as well as non-magnetic materials.
Radiographic testing employs the use of X-ray technology to find defects that adversely affect the strength of the part such as gas porosity, inclusions, shrinkage, cavity shrinkage, cold shuts, cracks, hot tears, and more. Radiographic testing is also used to verify weld repairs that have been completed.
Kovatch Castings is Nadcap-approved for non-destructive testing. In addition, we are proud to be approved to perform levels of NDT to the specifications of the following premier clients.