X-Ray testing is one of the best non-destructive inspection methods for detecting internal defects of castings.
In this method, the tested product is exposed under x-ray radiation. Parts of the radiation are absorbed by the product, and the remaining portion of the radiation exposes the radiographic film. Dense material withstands the radiation penetration, so the film is exposed to a lesser degree in those areas, giving the film a lighter appearance. Less dense materials allow more penetration and correlates to darker areas on the film. Any hole, crack or inclusion that is less dense than the casting alloy is revealed as a dark area. X-Ray testing is able to find internal defects of investment casting product including gas porosity and gas holes, shrinkage which appears as dendrite/filamentary/ jagged, cracks and so on.
