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Metris became a member of the Nikon group
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Turbine blades are designed for optimum aerodynamics and mass center location, and constitute of advanced metal alloy castings and composites to increase strength, resist extreme temperature, and avoid corrosion. Dense metal alloy materials set specific challenges for the inspection of turbine blades.
Inaccuracies in blade geometry and positioning may cause energy conversion efficiency loss and untimely blade failure. To guarantee optimum blade position and aerodynamic operation, tight tolerances apply to both the geometry and alignment of turbine blades.
Internal air cooling allows turbine blades to operate under extremely high temperatures up to around 1000°C. Blade wall thickness inspection is key to ensure optimum strength/cooling tradeoff across the entire aerofoil surface of blades. In addition, structural imperfections, including cracks and inclusions, may put blade lifetime at risk.
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Challenges when inspecting turbine blades
- Non-destructive inspection: x-ray and micro-CT is used to image and qualify the internal structure of turbine blades. Turbine blades are rather expensive samples.
- High inspection accuracy: both the freeform aerofoil surface of blades as well as specific features require accurate verification. In addition, internal walls thickness is subject to tight geometric deviations.
- Dense material: inspection of dense material requires powerful x-ray source that allows x-rays to travel through the blade.
- X-ray scattering: the inspection of dense materials potentially leads to x-ray scattering, which may cause inferior image quality.
- Fast inspection: turbine blades are inspected at different stages in the prototyping and production process: after concluding molding and specific machining and finishing steps.
- Fast CT reconstruction: in a production environment, it is important to quickly obtain inspection results.
- Larger specimens: turbine blades are somewhat larger in size and require an inspection cabinet that offers sufficiently space.
Recommended Metris solution
The XT H 450-LC is the advised solution for the inspection of turbine blades:
- Micro-focus source has a resolution of to 3µm
- Low cost of ownership thanks to open-tube technology
- High power 450kV micro-focus x-ray source
- Fast data capture and high-quality images
- Flexibility combined in a single system: X-ray for quick visual inspection, CT for in-depth analysis
- High-resolution digital imaging and CT processing
- Powerful and fully-featured post-processing analysis in Focus Inspection or VolumeGraphics
- Full protected cabinet fulfills all safety requirements
- High-efficiency linear detector offers 80% quantum detection efficiency
- 5-axis fully programmable tray manipulator with precision ball screws and linear slides
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Sample CT images and inspection results
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Turbine blade inspection
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Blade wall thickness analysis
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Typical applications
Application 1 : Detailed analysis of the internal structure of turbine blades
Besides inspecting the aerofoil surface of the blades, it is important to verify the internal structure of the blades. Industrial micro-CT traces inclusions, cracks and other material imperfections before committing to multiple machining process steps. Accurate blade profile images highlight the precise thickness of internal walls at any location along these walls.
Application 2 : Automated pass/fail inspection of blades
The entire inspection procedure on the XT H 450-LC can be defined and automated up-front. As a result, a series of turbine blades can be inspected automatically, granting a pass or fail label to each inspected blade.
Request information on Metris Computed Tomography systems
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