Inspectioneering Journal

Assessing Component Condition using Remote Metallography and Hardness Testing

By Oscar Quintero at M&M Engineering Associates. This article appears in the July/August 2013 issue of Inspectioneering Journal.

Remote metallography, in-place metallography, in-situ metallography, and field replication are all examples of typical trade names of this great tool used for assessing the condition of a metal component. Often this method is used to determine if a metal component was exposed to high temperatures, allowing the observation of the microstructure of such component without the sample being removed.

The sample is prepared by conventional metallographic methods of grinding, polishing, and etching with a specific acid solution tailored to the alloy chemistry to reveal grain structure. An acetate tape is then applied to the surface, dampened with acetone, and a replica of the microstructure is created. The replica can then be analyzed with a portable microscope and the results can be interpreted on-site. Some might refer to this as a “non-destructive technique”, but technically, it IS a destructive technique. If the technique is performed by an experienced operator, you will obtain great results by removing about 5 mils from the surface of the test subject. Effective remote metallography heavily depends on the technique, and the results are only as good as the surface preparation. An improperly prepared surface will still yield results, but if artifacts are introduced during surface preparation, such artifacts might prevent a proper assessment of the sample’s microstructure.

One of the drawbacks of in-place metallography is that it only offers a two dimensional view of a 3-D object (i.e., only x and y directions, but not the z-direction) (Figure 1). An alternate testing method would be required to examine the bulk material if you are looking for sub-surface or bulk material defects such porosity or shrinkage. It is also important to choose a proper area to do such a test. If in-place metallography is performed at a loaded area, then the affected area might turn into a stress riser, possibly resulting in cracking.

Figure 1 - Remote or in-place metallography can only offer a 2-D view of a 3-D object (sample). An alternate method is needed to detect bulk material defects.
Figure 1 - Remote or in-place metallography can only offer a 2-D view of a 3-D object (sample). An alternate method is needed to detect bulk material defects.

Remote metallography is primarily aimed at assessing an area that has been exposed to high temperatures, such as tubes in a boiler, structural components exposed to fire, or even gas turbine blades. In-place metallography can also discern the differences between different cracking damage mechanisms, such as creep, fatigue, stress corrosion cracking, intergranular attack, as well as many others. In this case, it is important to have someone who can interpret and understand the microstructural features. Figure 2 shows a typical remote metallography kit that includes acetate tape, grinding discs of different grits, and a portable grinding wheel, among other things.

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
Interested in unlimited access? VIEW OUR SUBSCRIPTION OPTIONS

Current subscribers and registered users can log in now.

Comments and Discussion

There are no comments yet.

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.

Training Solutions

Improve your skills in key mechanical integrity subjects.

Case Studies

Learn from the experience of others in the industry.


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.


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.


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

Videos & Webinars

Watch educational and informative videos directly related to your profession.


Commonly used asset integrity management and inspection acronyms.