I tried to remove the coating (600 microns thick) from the aluminium 6061 substrate (10*10*2 mm-flat), but I couldn't. What is your suggestion in this regard?
Original Message:
Sent: 08-22-2024 08:55
From: Rogerio Lima
Subject: Clarification on Preparing Free-Standing Coatings for Thermal Conductivity Measurement Using Laser Flash
Thanks a lot Georg for providing this very interesting reference! Besides... it is open access... which facilitates everything!
Dear Mathanbabu,
To complement Georg's paper, typically we have used low carbon steel puck-shaped substrates (10 mm diam. x 10 mm thick) to spray coatings for thermal diffusivity (TD) measurements via laser-flash, which is one of the steps to measure thermal conductivity (TC). The good thing about a puck-shaped substrate is the fact that the coating will not bend after being removed from the substrate; i.e., you will have a disk-shaped free-standing coating.
Besides, we typically sprayed it until it reaches a thickness of about 1 mm. A 1 mm thick free standing coating is easier to be removed from the substrate due to residual stress, easier to be handled manually and it improves the precision and accuracy of your TD measurement.
To remove the coating from the substrate, there are different methods, and some of them are well-described in paper provided by Georg. We typically here use acid dissolution, where the low carbon steel coated puck is put into a beaker having a 50-50 mixture of hydrochloric acid and nitric acid. If you do that you need to use a hood, because of some nasty fumes that will be produced. This acidic mixture dissolves the substrate and you have the free-standing coating. Then you have to wash the coating and properly dry it at temperatures of at least 100oC. This method works well, however, there is a drawback. As pointed out in the paper provided by Georg, the acid may attack the coating, thereby creating porosity, which can affect the TD measurement.
Another alternative is to produce the same coating and substrate combo, and dip it into liquid N2. Let it stay there for a about a minute. Then remove it and heat it the substrate side using an industrial heat gun (i.e., a powerful hair drier). The CTE difference will tend to make the coating pop-off the substrate (mainly if the coating is a ceramic). The drawback is, not everyone has liquid N2 available all the time.
I hope it helps.
Cheers!
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Rogerio Lima, PhD
Senior Research Officer
National Research Council of Canada
Fellow of ASM International (FASM)
President of Thermal Spray Society (TSS)
e-mail: rogerio.lima@nrc-cnrc.gc.ca
Original Message:
Sent: 08-22-2024 07:20
From: Georg Mauer
Subject: Clarification on Preparing Free-Standing Coatings for Thermal Conductivity Measurement Using Laser Flash
Dear Mariappan:
Please have a look here:
R. Vaßen, E. Bakan, S. Schwartz-Lückge, Influence of Substrate Removal Method on the Properties of Free-Standing YSZ Coatings, Coatings, 2021, 11(4), p 449
Regards,
Georg
--
PD Dr.-Ing. Georg Mauer
Institute of Energy Materials and Devices
IMD-2: Werkstoffsynthese und Herstellungsverfahren (Materials Synthesis and Processing)
Tel. +49 2461 61-5671
Fax +49 2461 61-2455
E-Mail g.mauer@fz-juelich.de
Internet https://www.fz-juelich.de/de/imd/imd-2
Regards,
Georg
--
PD Dr.-Ing. Georg Mauer
Institute of Energy Materials and Devices
IMD-2: Werkstoffsynthese und Herstellungsverfahren (Materials Synthesis and Processing)
Tel. +49 2461 61-5671
Fax +49 2461 61-2455
E-Mail g.mauer@fz-juelich.de
Internet https://www.fz-juelich.de/de/imd/imd-2
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Georg Mauer
Forschungszentrum Julich GmbH
Jülich
g.mauer@fz-juelich.de
Original Message:
Sent: 08-22-2024 05:22
From: Mathanbabu Mariappan
Subject: Clarification on Preparing Free-Standing Coatings for Thermal Conductivity Measurement Using Laser Flash
Dear TSS community,
I am currently working on a project that involves measuring the thermal conductivity of Thermal Barrier Coatings (TBC) using the Laser Flash technique. I would appreciate some clarification on the process of preparing free-standing coatings for this purpose.
Could you please provide guidance on the best practices for detaching the coating from the substrate and any specific considerations to ensure accurate thermal conductivity measurements?
Your expertise would be invaluable in helping me proceed with this work.
Thank you for your time and assistance.
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Mathanbabu Mariappan
Senior Project Associate
Center of excellence for hypersonics
Department of Aerospace Engineering,
Indian Institute of Science, Bangalore, INDIA
Ph No: +91 9787790604
Email; mathanbabum@iisc.ac.in
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