Radiographic Testing in Aerospace Materials
What Is Radiographic Testing?
Radiographic Testing (RT) is a non-destructive testing (NDT) method that uses penetrating radiation — X-rays or gamma rays — to create images of a component’s internal structure. Radiation passes through the material and is differentially absorbed depending on material density and thickness. The transmitted radiation is captured on film (conventional radiography), digital detector arrays (computed radiography, DR), or processed by computed tomography (CT) to create two-dimensional projection images or three-dimensional volumetric reconstructions of the component’s interior.
In aerospace, where structural integrity is paramount and the consequences of undetected internal defects—porosity, inclusions, cracks, delaminations, and wall-thickness variations—can be catastrophic, radiographic testing is one of the most widely mandated NDT methods for production quality assurance and in-service inspection programs.
Types of Radiographic Testing Used in Aerospace
Conventional Film Radiography (X-Ray Film)
The classical technique: X-ray film in a light-tight cassette is placed behind the component, exposed to radiation, then chemically developed. Film radiographs provide a permanent, high-resolution record of the component’s internal condition. Still widely used for weld inspection, casting evaluation, and baseline documentation in aerospace.
Computed Radiography (CR)
Photostimulable phosphor (PSP) plates replace film — exposed plates are scanned by a laser, releasing stored energy as light, which is captured by a photomultiplier to produce a digital image. CR provides digital images with a wide dynamic range and immediate viewing — eliminating film-processing chemicals while maintaining compatibility with existing X-ray equipment.
Digital Radiography (DR)
Flat-panel digital detector arrays provide immediate real-time digital images — used for high-throughput production inspection where rapid feedback is required. DR offers the highest sensitivity and resolution of the digital methods, with image acquisition in seconds rather than minutes.
X-Ray Computed Tomography (CT)
CT acquires multiple radiographic projections from different angles as the component is rotated, reconstructing a complete 3D volumetric image of the internal structure. CT is the highest-capability radiographic technique: it localizes defects in 3D, measures porosity volume and distribution, quantifies wall thickness, and provides dimensional measurements of internal features without any sectioning.
Gamma Ray Radiography
Radioactive isotopes (Ir-192, Se-75, Co-60) produce gamma rays that penetrate thicker sections than most X-ray systems — useful for field inspection of thick-walled components, but with lower image quality than X-ray for thinner sections.
Defects Detected by Radiographic Testing in Aerospace
- Porosity: Gas pores in welds, castings, and additive-manufactured parts — detected as rounded dark spots in the radiographic image
- Inclusions: Foreign material (slag, tungsten, oxide) in welds — detected as irregular light or dark regions
- Cracks: Linear planar defects — detected as thin dark lines (must be oriented close to the beam direction for reliable detection)
- Lack of fusion / incomplete penetration: In welds — detected as elongated dark regions
- Delaminations: In composite laminates — detected by CT or edge-on radiography
- Wall thickness variations: In castings and tubes — measured by dual-wall radiographic exposure
- Core density variations: In honeycomb sandwich structures — detected by through-transmission radiography
Aerospace-Specific RT Standards and Requirements
- ASTM E94: Guide for radiographic examination — the foundational ASTM RT standard
- ASTM E1742: Standard practice for radiographic examination
- ASTM E1570: Standard practice for CT examination of castings
- SAE AMS 2630: X-ray inspection of aerospace castings and forgings
- ASNT SNT-TC-1A / NAS 410: Personnel qualification and certification for NDT
- MIL-STD-453: Inspection, radiographic (military specification)
- NADCAP: National Aerospace and Defense Contractors Accreditation Program — mandatory accreditation for RT laboratories performing aerospace inspection
Industry Applications
Castings: Aluminum, titanium, and nickel superalloy investment and sand castings for engine, structural, and landing gear components are routinely radiographed to detect porosity, shrinkage, and inclusions before machining.
Welds: Pressure vessel and structural welds in aircraft fuel systems, hydraulic systems, and engine components are radiographed per AMS and ASTM standards to verify internal weld quality.
Additive Manufacturing: Laser powder bed fusion (LPBF) and directed energy deposition (DED) parts for aerospace structures require RT and CT for porosity mapping and geometric verification—particularly of internal channels and lattice structures.
Composite Structures: CT is used to characterize fiber volume fraction, void content, delaminations, and foreign-object inclusions in carbon-fiber composite structural components.
Engine Components: Turbine blade wall thickness, cooling channel geometry, and coating integrity in high-pressure turbine hardware are characterized by high-resolution CT as part of design validation and manufacturing quality programs.
Conclusion
Radiographic testing — spanning conventional film X-ray, computed radiography, digital radiography, and industrial CT across castings, welds, additive manufactured parts, and composite structures per ASTM, AMS, and NADCAP-accredited protocols — provides the internal defect detection and volumetric characterization data essential for structural integrity assurance in aerospace manufacturing and in-service inspection programs. Selecting the right radiographic technique for the specific material, geometry, defect type, and sensitivity requirements determines whether RT reliably detects porosity, inclusions, cracks, and wall-thickness variations before they compromise airworthiness — making technique selection and personnel qualification as critical to inspection reliability as any equipment capability.
Why Choose Infinita Lab for Radiographic Testing?
Infinita Lab offers comprehensive radiographic testing services — from conventional film X-ray and computed radiography through industrial CT scanning — across its network of 2,000+ NADCAP-accredited and ASTM-compliant testing labs in the USA. Our advanced equipment and expert NDT professionals deliver highly accurate and prompt results, helping aerospace manufacturers achieve quality compliance and airworthiness confidence.
Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090 to learn more about our services and how we can support you. Request a Quote.
Frequently Asked Questions
What is the difference between 2D radiography and CT scanning? Conventional 2D radiography produces a single projection image showing internal features as superimposed shadows — depth information is lost. CT scanning acquires multiple projections from different angles and reconstructs a complete 3D volumetric image — enabling precise localization, sizing, and characterization of internal defects in three dimensions.
What is NADCAP accreditation for radiographic testing? NADCAP (National Aerospace and Defense Contractors Accreditation Program) is the industry-managed accreditation program for special processes used in aerospace manufacturing. NADCAP accreditation for NDT including RT requires demonstration of compliant procedures, equipment calibration, personnel qualification, and quality management systems — and is mandatory for suppliers to most major aerospace primes.
Why does crack orientation matter in radiographic testing? Radiography detects cracks by differential radiation absorption. A crack oriented parallel to the X-ray beam (edge-on) creates maximum thickness change and is readily detected. A crack perpendicular to the beam (face-on) creates essentially no thickness change and may be completely undetectable. For crack-critical applications, ultrasonic testing or PT/MT are used alongside RT because they are more sensitive to all crack orientations.
What thickness of material can X-ray radiography inspect? This depends on the material and X-ray energy. For aluminum alloys, conventional X-ray inspection covers up to ~150 mm. For steel, practical limits are typically 75–100 mm with high-energy X-ray or Ir-192 gamma sources. For titanium and nickel superalloys, sections up to 50–75 mm are inspectable with appropriate equipment.
What ASTM standards govern radiographic testing of aerospace castings? ASTM E1742 governs radiographic examination practices. ASTM E1570 covers CT examination of castings. ASTM E155 provides reference radiographs for aluminum and magnesium castings. SAE AMS 2630 is the aerospace-specific X-ray inspection standard for castings and forgings
