where expertise comes together - since 1996

Web's Largest Portal of Nondestructive Testing (NDT)
Open Access Database (Conference Proceedings, Articles, News), Exhibition, Forum, Network

All Forum Boards
Technical Discussions >
Phase shift in measurement of oxide layer thickness
Career Discussions
Job Offers
Job Seeks
Classified Ads
About NDT.net
Articles & News

NDTSS - Non Destructive Testing Society of Singapore
Visit us for 15th APCNDT 2017

364 views
07:21 Sep-28-1999
Tomás Gómez-Acebo
Phase shift in measurement of oxide layer thickness

Dear colleages, I have recently joined your discussion forum.
I would appreciate comments or suggestions about this topic.
When measuring with a 25 MHz probe the magnetite layer formed into the tubes of steam boilers (about .2 to 1 mm thick), there is a phase shift between the two echos in the RF signal: the first echo from the steel-oxide interface, and the second from the final oxide interface. How can this be interpreted?
Additionally, is there any way to distinguish between the two sub-layers of the oxide? Both have very similar chemical composition but slightly different porosity and microstructure: the inner (in contact with the steel) is layered, and the outer has columnar magnetite grains.
In the time-domain signal it is impossible to see anything that suggests the interface between the sub-layers, but what about the frequency-domain, or something else?
Best regards
Tomas Gomez-Acebo


 
00:46 Sep-28-1999

Paul A. Meyer

R & D,
GE Inspection Technologies,
USA,
Joined Nov 1998
47
Re: Phase shift in measurement of oxide layer thickness final oxide interface. How can this be interpreted?
: Additionally, is there any way to distinguish between the two sub-layers of the oxide? Both have very similar chemical composition but slightly different porosity and microstructure: the inner (in contact with the steel) is layered, and the outer has columnar magnetite grains.
: In the time-domain signal it is impossible to see anything that suggests the interface between the sub-layers, but what about the frequency-domain, or something else?
: Best regards
: Tomas Gomez-Acebo




 


© NDT.net - The Web's Largest Portal of Nondestructive Testing (NDT) ISSN 1435-4934

Open Access Database, |Conference Proceedings| |Articles| |News| |Exhibition| |Forum| |Professional Network|