Category Archives: metallography

Microscope Monday

posted January 2020
SEM image of snowflake

Snowflake

Corrosion Pit

Copper corrosion pit

Twenty years ago, MEE Lab Manager, Kurt Schenk, figured out a way to capture the beauty of a freshly fallen snowflake with an SEM. Those images and hundreds of others taken over the years in our laboratory have been saved in a file on our network simply called “cool images”.

Five years ago, we thought it would be fun to share some of our favorite cool images on social media and the MEE Facebook page was created. We have since posted over 180 images. Some are just-for-fun, like snowflakes, insects and even the grooves in an LP, but most of the images are the kind of things we observe in our daily work. We have posted images that highlight fracture mechanisms, unique microstructures and particular imaging techniques used to gather critical data needed in a failure analysis investigation.

Journal of Failure Analysis and Prevention

Alkaline Carbonate SCC Failures at a Refinery, co-written by MEE staff engineers, Ryan Haase and Larry Hanke was recently published in the Journal of Failure Analysis and Prevention ( First Online: January 16, 2018)

A metallurgical evaluation was performed to investigate two failures from carbonate-containing sour water service at a refinery. The paper details the visual, SEM/EDS, metallographic, and microhardness evaluations used to determine the failure mechanism for each refinery component.

 

 

 

 

 

Graphitic Corrosion Case Study

posted January 2017

We were asked to determine the mechanism and possible causes of corrosion of a cast iron sanitary sewer pipe. Metallurgical testing and EDS analysis pointed to graphitic corrosion. With graphitic corrosion there is no reduction in the size or shape of the pipe but the strength of the material is severely reduced.

Cross section of vent pipe.

Cross section of vent pipe.

The Vent Pipe case study explains in more detail how this type of corrosion mechanism is identified, causes and our recommendations to the client.

All of the case studies on our website come from our files. They have been edited to present a more casual writing style than our formal reports, but generally they follow the structure of our reports and give an overview of the findings and conclusions from an investigation.

The Intern Experience at MEE

posted August 2016

Interns, Reid Schur and Josh Polzin, were a welcome addition to our team this summer.

Reid completed a project comparing the chemical vs mechanical test methods used in ASTM  D3483, Standard Test Methods for Accumulated Deposition in a Steam Generator Tube. We will use the information from his work to help our customers decide on the best test method to use with their specific projects. Josh spent a lot of his time in the metallographic laboratory doing sample preparation and testing material removal rates for the automatic polisher.

Both can also add welding and engineering design to their resume after creating this bike rack for our staff who commute to work by bike. Thank you Reid and Josh and good luck in your engineering careers.

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MEE Hires Second Intern

posted June 2016

Welcome to summer intern, Josh Polzin. Josh will be a freshman in the college of engineering at the University of Michigan, Ann Arbor this fall. We met Josh last summer when he was a high school senior attending the Minnesota ASM materials science camp. Students spend one day of the camp in the MEE laboratory learning about and using scanning electron microscopes, Rockwell hardness testers, microhardness testers and a variety of light microscopes.  Apparently, Josh liked we he saw here at MEE and talked with principal engineer, Larry Hanke,  about a possible internship.   We were pleased to have the opportunity and resources to hire a second intern for the summer. Working under the direction of a materials engineer, Josh will be testing alternative procedures for cold mounting metallographic specimens among other projects in the MEE metallographic laboratory.

 

 

Update to MEE website

posted April 2016

A fire inside a three story stainless steel chamber is the subject of the latest case study added to our webpage.  The goal of the evaluation was to determine what material required replacement or repair, and what material could remain in service. Thus, the evaluation could only be nondestructive. This required an on-site investigation and in situ metallographic examination.

With materials engineering expertise in the behavior of stainless steel under certain conditions ( in this case, elevated temperatures in a carbon-rich environment) and in the analysis of metallographic images, we were able to provide the client with the information he needed to make informed decisions on the future use of this equipment.

Carburization – Case Study

posted August 2015

An interesting new case study has been added to our website. We were asked to investigate the failure of perforated steel plates from a gas-fired boiler.  Initial macroscopic examination  was consistent with a corrosion fatigue mechanism.

Stainless steel perforated plate

Further examination using a metallographic light microscope revealed an unusually high concentration of carbides that became more concentrated in a gradient toward the original outer surfaces of the plates. Read the complete case study to learn how carburization of  the plate material during normal service had reduced the strength of the plates.

While determining the failure mode is an important step in any fracture investigation, there is often an underlying cause that may be of greater importance to mitigating or preventing similar failures. MEE’s engineering staff  specialize in the behavior of materials and how their structure affects service performance. Our comprehensive reports combine reliable, analytical data with a sound engineering perspective to provide practical cost-effective solutions to our customers.

 

Not all of our projects come to us in small packages. How do we get that 7′ long, 6″ diameter steel tube or the 4′ diameter industrial fan under a microscope?
Sample preparation often begins in our machine shop. The MEE shop is equipped with a variety of cut-off saws, a Bridgeport mill, plasma cutter, band saws, and other specialty tools necessary to cut out representative sections from large pieces for further preparation before a metallographic and/or microscopic examination.
Before any cutting is done, it is crucial to understand that proper sample preparation methods are necessary for accurate materials analysis. Care must be taken when cutting a sample from a larger piece to not contaminate or alter the area of interest.
If you have questions about sample preparation, preservation or handling, read MEE’s ten commandments of sample handling and preservation in our online Handbook of Analytical Methods for Materials.

Our hands-on expertise extends outside the microscopy lab.

Our hands-on expertise extends outside the microscopy lab.

Stress corrosion cracking in a chemical storage tank, hydrogen damage in a boiler tube, fatigue fracture in titanium sternal plates are just a few of the case studies on our website.   They were specifically chosen to highlight the variety of projects we see in our laboratory and more importantly, demonstrate the thorough, analytical approach we take on all of our projects.

Engineering Consulting_Failure_

Blade failure on wind generator

The goal of a failure analysis is to determine the how and why of a failure.  Laboratory testing at MEE, which may include scanning electron microscopy, Rockwell hardness testing, corrosion testing,  and metallographic evaluation  can help us get answers to the how and why but we also like to work with our client to answer the question of “now what”  in order to minimize future risk of failure.

 

 

MEE, Inc  is a long- time sponsor of the MN Chapter of ASM International Materials Science Camp for high school students. Thirty students got to spend a day in our laboratory learning about and using scanning electron microscopes, Rockwell hardness testers, microhardness testers and a variety of light microscopes. Three on our staff, Larry, Kurt and Neal, are also camp mentors for the entire week of camp. MEE staff enjoys the time they get to spend with these bright, motivated students and hope the students time spent in our lab gave them a deeper understanding of the field of materials science and engineering principles.

 

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