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Metallographic Studies on a Defective Plate Heat Exchanger

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Published/Copyright: May 8, 2013
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Practical Metallography
From the journal Practical Metallography Volume 44 Issue 5

Abstract

A defective plate heat exchanger is investigated and the main aim is to find the reason for that damage and how this can be avoided. The plates are made of stainless steel (Cr17Ni12Mo2; material No. 1.4401) and are brazed with pure copper.

After cutting and examination of the heat exchanger no relevant corrosion of the copper braze is observed. Metallographic investigations by light optical microscopy (LOM) show that copper has diffused into the steel plates (liquid metal embrittlement). Using various etchings the areas of the steel plates, which are influenced by the copper diffusion, become visible and also an additional phase is observed. Electron beam micro analysis (EBMA) show that this phase is a chromium-rich ferrite.

Kurzfassung

In der vorliegenden Studie wurde ein defekter Plattenwärmetauscher untersucht. Es sollte herausgefunden werden, warum der Schaden entstand und wie er zukünftig vermieden werden kann. Die Platten bestanden aus nichtrostendem Stahl (Cr17Ni12Mo2; Materialnummer: 1;4401) und waren mit reinem Kupfer verlötet.

Nach dem Zersägen und beim Untersuchen des Wärmetauschers wurde keine wesentliche Korrosion der Kupferlötung festgestellt. Metallographische Untersuchungen anhand von Lichtmikroskopie ergaben, dass das Kupfer in die Stahlplatten eindiffundierte (Flüssigmetallversprödung). Über das Ätzen mit verschiedenen Ätzlösungen wurden diejenigen Stellen in den Stahlplatten sichtbar, die von der Kupferdiffusion betroffen waren. Darüber hinaus wurde eine zusätzliche Phase beobachtet. Durch eine Elektronenstrahl-Mikroanalyse (ESMA) wurde festgestellt, dass es sich dabei um chromreichen Ferrit handelte.

Die beobachteten Phänomene können durch eine zu hohe Löttemperatur erklärt werden.

Übersetzung: C. Kriele

Roland Haubner is Ao.Univ.Prof. at TU-Vienna. His fields of activity till now were industrial tungsten production, CVD (Chemical Vapor Deposition) and the low-pressure diamond deposition. He is also involved in materials characterization, ceramics and corrosion. http://cvd.cta.tuwien.ac.at/Haubner/haubner.html

Susanne Strobl is working as a scientific officer at the Institute of Chemical Technologies and Analytics (TU-Wien) and is teaching supervisor of metallography. She studied chemistry and her doctoral thesis was about sintered steels.

Literatur/References

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Received: 2006-11-15
Accepted: 2007-1-16
Published Online: 2013-05-08
Published in Print: 2007-05-01

© 2007, Carl Hanser Verlag, München

Articles in the same Issue

  1. Contents/Inhalt
  2. Inhalt / Contents
  3. Editorial
  4. Editorial
  5. Technical Contributions/Fachbeiträge
  6. Elektronenmikroskopische Untersuchung der Mikrostruktur von pseudoelastischen NiTi-Stents
  7. Metallographic Studies on a Defective Plate Heat Exchanger
  8. Correlation between Crystal Orientation, Channeling Contrast and Topography during FIB Milling of Cu Studied by FIB, EBSD, SEM, and AFM
  9. Fabrication and Modification of Photonic Structures with Focused Ion Beam
  10. Novel Applications of a Focused Ion Beam Workstation for Specimen Preparation and Nanostructuring
  11. Automated X-Ray Elemental Analysis in Three Dimensions Using a Dual Beam-Focused Ion Beam System
https://doi.org/10.3139/147.100339

Articles in the same Issue

  1. Contents/Inhalt
  2. Inhalt / Contents
  3. Editorial
  4. Editorial
  5. Technical Contributions/Fachbeiträge
  6. Elektronenmikroskopische Untersuchung der Mikrostruktur von pseudoelastischen NiTi-Stents
  7. Metallographic Studies on a Defective Plate Heat Exchanger
  8. Correlation between Crystal Orientation, Channeling Contrast and Topography during FIB Milling of Cu Studied by FIB, EBSD, SEM, and AFM
  9. Fabrication and Modification of Photonic Structures with Focused Ion Beam
  10. Novel Applications of a Focused Ion Beam Workstation for Specimen Preparation and Nanostructuring
  11. Automated X-Ray Elemental Analysis in Three Dimensions Using a Dual Beam-Focused Ion Beam System
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