Inspectioneering
Inspectioneering Journal

Simplifying Complex Failures with EDX Images

By Matthew Bell, P.Eng., Sr. Materials Engineer at IRISNDT. This article appears in the May/June 2021 issue of Inspectioneering Journal.
3 Likes

Introduction

Failure analysis can be perceived as a mystery box for personnel that are not involved: they send in a failed component and need to know why it failed, if the problem could exist elsewhere, how to inspect for it, and ultimately how to prevent recurrence. One of the greatest challenges for a failure analyst is to present complex information clearly for an audience that may not have the same depth of knowledge on specialized subjects. Sometimes, a failure mechanism can be summarized with an image that can tell the whole story – a “Eureka” Image. The old adage, “a picture is worth a thousand words,” is particularly relevant.

This article summarizes three examples where a technique called Energy Dispersive X-ray (EDX) mapping was used to clearly illustrate the failure mechanism, producing a “Eureka” image. The first example is about how an interesting, layered scale in carbon steel piping summarized how the cycling conditions affected the failure mechanism. The second example shows how a region missing scale in a carbon steel crude heater tube summarized the active corrosion mechanism. The last example is about how a missing alloying element led to a diagnosis of dealloying in a nickel aluminum bronze valve.  First, a brief explanation of the EDX technique is provided so that the Eureka images can be interpreted.

EDX Technique Explained

The Scanning Electron Microscope (SEM) is a valuable tool for a failure analyst to examine samples at high magnifications. In brief, an SEM functions by bombarding a sample with electrons in a vacuum chamber. The incident electrons interact with the near surface atoms in a sample. The incident energy causes many interactions within the sample. Some of the useful interactions used during a failure analysis include: 

  • Secondary Electron (SE) imaging, useful for examining topographical features, 
  • Backscatter Electron Detection (BSD), useful for examining compositional differences, and 
  • Energy Dispersive X-ray (EDX) analysis, useful for determining and quantifying the elements present in a sample. 

EDX analysis is the most relevant technique for the following three case studies discussed. EDX forms the basis of chemical composition analysis by a process called X-ray Fluorescence (XRF). In brief, the incident electrons excite the electrons in a sample and produce X-rays characteristic to the elements present. The resultant X-rays are detected and converted into information about what elements are present. 

This content is available to registered users and subscribers

Register today to unlock this article for free.

Create your free account and get access to:

  • Unlock one premium article of your choosing per month
  • Exclusive online content, videos, and downloads
  • Insightful and actionable webinars
GET STARTED
Interested in unlimited access? VIEW OUR SUBSCRIPTION OPTIONS

Current subscribers and registered users can log in now.


Comments and Discussion

Posted by Aldrin Faustino on June 30, 2021
Very Informative Log in or register to read the rest of this comment.

Posted by Rajaram Chidambaram on July 20, 2021
Hi Matthew, Excellent paper illustrating... Log in or register to read the rest of this comment.

Add a Comment

Please log in or register to participate in comments and discussions.


Inspectioneering Journal

Explore over 20 years of articles written by our team of subject matter experts.

Company Directory

Find relevant products, services, and technologies.

Talent Solutions

Discover job opportunities that match your skillset.

Case Studies

Learn from the experience of others in the industry.

Integripedia

Inspectioneering's index of mechanical integrity topics – built by you.

Industry News

Stay up-to-date with the latest inspection and asset integrity management news.

Blog

Read short articles and insights authored by industry experts.

Expert Interviews

Inspectioneering's archive of interviews with industry subject matter experts.

Event Calendar

Find upcoming conferences, training sessions, online events, and more.

Downloads

Downloadable eBooks, Asset Intelligence Reports, checklists, white papers, and more.

Videos

Watch educational and informative videos directly related to your profession.

Acronyms

Commonly used asset integrity management and inspection acronyms.