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Flexible Assessment of Thermal Transport Properties of Thermal Barrier Systems Measured by The Hot Disk Method
Caroline Goddard1, Tobias Öhman2; Nicolaie Markocsan2; Mattias Gustavsson3, Lars Östergren4
1-University of Manchester; 2-University West; 3-Hot Disk AB; 4-Volvo Aero
Project Supported by VINNOVA
Participants: Univ. West / Univ. Manchester, Hot Disk AB, VAC
Requirements of Thermal Conductivity of TBCs
Performance of layers (lab) – LFLower-cost/flexible testing – HDQuality Control? (on-line) – HD
Hot Disk Sensor
Laser Flash Technique Transient Plane Source (Hot Disk)
Most accepted method New possibility
Non Contact method Contact method
Laboratory method only Potential to be used directly on components
Measures Thermal Diffusivity then calculates Thermal Conductivity
Measures Thermal Conductivity directly
Higher equipment cost Lower equipment cost
Need to know the thickness, density and specific heat capacity
Need to know the thickness of the sample and its dimensions
Must be a specific size and shape
HD Technique – Apparent (Thin Film) vs. Bulk Properties
Apparent Coating Properties - Setup
Influence of Surface Roughness
Comparisons LF vs. HD
• The results show that it is possible to obtain comparable results between the Hot Disk method and the Laser Flash method for coatings A and B.
• Coating C did not show agreement with LF.
Comparisons LF vs. HD
• The surface roughness has a significant effect.
• It is possible to develop a method for measuring thermal conductivity of TBC by “Thin Films” apparent property approach.
• Approach does not allow non-destructive testing.
• Zirconia coatings range from 300µm thick to over 700µm thick and the method cannot reliably measure coatings 550µm or thicker.
• ( Presently preparing for tests at elevated temperatures. )
Other Possibilities – Quality Control?
• APPARENT properties (less stable) if coating thinner than 0.5 mm
• BULK properties (stable), only if coating thicker than 0.5 mm
• Investigating inhomogeneous variations vs. depth from surface, for thicker coatings basis (on-line testing)