Radiographic Testing
Radiographic Testing (RT) is a non-destructive testing method that uses X-rays or gamma rays to image the internal structure of a part. It detects hidden discontinuities such as porosity, voids, inclusions, cracks, and lack of fusion by placing the part between the radiation source and a film or digital detector; density and thickness variations create a radiograph revealing internal conditions.
In CNC cells, fabrication bays, and weld lines, Radiographic Testing is scheduled after process steps that can create hidden internal flaws, particularly welding and casting. The part is cleaned, fixtured, and aligned so the area of interest sits centered in the beam path; exposure settings are then chosen from material thickness, density, and required sensitivity. On metal parts, RT confirms whether a weld bead contains slag inclusions, porosity, cavities, or incomplete fusion, and whether a casting contains shrinkage porosity or internal voiding that could fail under load. RT is valued for producing a permanent inspection record using traditional film or digital systems such as computed radiography and real-time digital methods. In the quality system, radiographs are interpreted against acceptance criteria, documented for traceability, and used to decide rework, repair, or rejection.
What makes RT a volumetric inspection method?
It evaluates internal density variations through the full thickness of the part, so it is used to identify internal discontinuities rather than only surface conditions.
What defects does RT detect best?
It is especially effective for porosity, slag inclusions, voids, cavities, shrinkage, and weld discontinuities that create measurable density changes.
What is the main limitation of RT on welded or machined parts?
RT depends on radiation passing through the defect and creating contrast on the detector, so defect orientation, overlap, and section thickness can reduce detectability.