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Improving defect analysis with X-ray CT

by Ludovic on 16 Aug 2021 at 15h43
Because it can be used on a wide range of products and offers comprehensive information on previously inaccessible characteristics of parts, X-ray computed tomography (CT) is gaining popularity in industrial quality control. As a non-destructive imaging technique, X-ray CT allows the inspection of defects in the material's structure such as cracks, porosities or inclusions. A multitude of industrial applications require the use of computed tomography, to control manufacturing objects during the production stage and locate important defects on parts.

X-ray CT offers comprehensive defects inspection 

Industrial X-ray Computed Tomography has made significant progress in recent years, with better resolution and faster reconstruction for 3D volume data. For quality control, full 3D scanning of samples and the ability to create cross-sectional images from any angle offers up additional analysis-related and time-saving opportunities in the industrial sector.
Cracks, voids, porosity, and inclusions analysis reveal important physical properties questioning the quality of the component and its performance characteristics. CT provides the ability to detect, identify and quantify defects and visualize with 3D representations. Using a color code, defects visualization by sizes, shapes, or other criteria can be performed and the analysis results can be output in different formats and used to improve products quality. 

How defects are detected with X-ray CT 

Regarding defect detection, the size of the inclusions can be indicated in different colors on the component itself using automated porosity analysis. As a result of this defect detection process, the quality of the casting process or component stability may be determined. Indeed, for defect detection with X-ray CT you are able to localize anomalies and identify ROIs (Regions of Interest) as well as determine defect types with the exact 3D reproduction for their shape. 
When using X-ray CT to carry out defect analysis, there are a few factors to keep in mind:
  1.    -   Defect size: for a greater resolution, you need at least set up your scan to a 3x3x3 matrix of voxels indicating your defects. In fact, a scan at 50 µm resolution allows to detect defects of 150 µm size.

   -   Contrast sensitivity: this depends on the size of the defects – the larger the defect the least contrast is needed whereas for small defects it is important that contrast is higher
From a scanning set-up point of view,  it's difficult to find a balance between scan resolution and contrast when carrying out defect analysis with X-ray CT, since several of the factors that improve contrast may also lower resolution. 

Benefits of analyzing defects with X-ray CT 

-  3D rendering results can precisely identify internal defects such as porosity, inclusion, or voids 
-  The scan results are quantified in volume, location, and size for each defect with a color code 
-  Your product quality will be increased through fast feedback to production processes  
-  No need to cut parts and lose crucial information to locate and detect defects 
-  Non-destructive inspection of defects saves time through simple visualization & inspection and resources through early defect detection 

Tomographic results for defect analysis 

Image 1
Location of defects around the part 
Image 2 
Inconel part  
150 kV -Voxel size: 8µm
Defects are detected each with a color code representing theirs sizes in diameter (mm)  
To ensure total product integrity, failure is simply not an option for every industry. Thus, there are many challenges to producing and developing high-quality products. 
Non-destructive testing is an innovative and efficient technology to check products since it detects flaws and defects in components and materials without destroying or changing them. 3D non-destructive scanning, with the benefit of noncontact putting away the risk of part degradation, offers greatly accurate features to validate final products. Indeed, X-ray CT is a very precise tool to visualize and quantify defects in 3D. X-rays are very sensitive to density material variations, and defects at different scales, down to hundreds of nanometers, can be detected.