Category Archives: metallography

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.

 

IMG_1069IMG_1062

IMG_1102

Principal Engineer, Larry Hanke, spoke at the spring seminar of the Wisconsin chapter of the International Association of Arson Investigators (IAAI) on materials analysis for fire investigations The purpose of the presentation was to describe and demonstrate what a metallurgical engineer can add to the investigation of a structural fire or explosion. His presentation included an overview of important principles of metallurgical and materials science,  descriptions of the analytical methods used in finding the modes of failure, and case studies of investigations at MEE where material science has been instrumental in the investigation.

The following image was taken at MEE using a metallographic microscope.

Melting from electrical arcing on corrugated stainless steel tubing perforation

Melting from electrical arcing on corrugated stainless steel tubing perforation