Failure Analysis

Hydrogen Embrittlement – Part 1

Posted by Rob in Failure Analysis on 29. Nov, 2010 | 1 Comment

Hydrogen Embrittlement – Part 1 High Strength Steels Achilles Heel The Phenomenon Sudden brittle fracture in high strength steels resulting from hydrogen embrittlement represents an extremely dangerous phenomenon to industry, particularly since it is usually the result of factors that occur during the manufacturing process. Hydrogen embrittlement reduces ductility, often to the point where metals [...]

Analyzing Contaminants, Stains and Debris – Part 1

The impact of contaminants, stains or debris can range from nuisance to root cause of catastrophic failure. The nature of these materials presents some special analytical challenges. First, only extremely small amounts of material are usually present and available for analysis. Second, they typically result from an unintended and therefore undocumented variable in the manufacturing [...]

Biological Corrosion of Metals

Desulfovibrio vulgaris, a sulfur reducing bacteria, generate hydrogen sulfide as a metabolic bi-product. This species has been implicated in MIC – Microbiologically Induced Corrosion – in iron, steel, stainless steel, aluminum, zinc and copper alloys. The cost of corrosion to the US economy is estimated at 4.2% of the Gross National Product according to a [...]

Fatigue and its Failure Analysis

On May 11th, 1842 the first major railroad disaster in history set off a chain of events which led to the discovery of the phenomenon that we now know as fatigue failure. The Paris – Versailles Express, hurtling down the tracks at the then astounding speed of 50 miles per hour, exploded in flames when [...]

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Hydrogen Embrittlement – Part 3

Posted by Rob in Failure Analysis on 13. Dec, 2010 | 2 Comments

Hydrogen Embrittlement – Part 3 High Strength Steels Achilles Heel Susceptible Materials While some stainless steel grades are susceptible, high strength steels with tensile strengths and hardness above 130,000 psi and Rockwell C35, respectively, are the most prone to hydrogen embrittlement. Steels below these tensile and hardness levels are generally immune. Why? Increasing hardness, most [...]

Hydrogen Embrittlement – Part 2

Posted by Rob in Failure Analysis on 06. Dec, 2010 | 1 Comment

Hydrogen Embrittlement – Part 2 High Strength Steels Achilles Heel The Metallurgical Phenomenon Hydrogen atoms are the smallest of any element. So small, that they easily travel between iron atoms. The boundaries between crystals, or grains, which are the structure of metals, are gapping canyons in relative size to hydrogen atoms. Once absorbed, hydrogen atoms [...]

Analyzing Contaminants, Stains and Debris – Part 2

Posted by Rob in Contaminant Analysis on 06. Jul, 2010 | 2 Comments

Abrasive Contaminants A gas transmission compressor shaft in a facility in China began showing excessive wear at the bearing journals during initial mechanical testing (spinning) of the compressor. The plant operator suggested the tin based babbitt bearings were the source of the wear. Our analysis of the bearings showed that the babbitt and bond fully [...]

Microbiologically Induced Corrosion – Prevention and Analysis

Posted by Rob in Corrosion Analysis on 04. Jun, 2010 | 2 Comments

The first line of defense against Microbiologically Induced Corrosion (MIC) is cleanliness. General corrosion prevention techniques are a good starting point since once corrosion begins, the introduction of MIC producing bacteria will greatly accelerate the process. Once bacteria are established, both anaerobic bacteria which “tunnel” into metal, and other forms which adhere under biofilms, are [...]

Microbiologically Induced Corrosion

Posted by Rob in Corrosion Analysis on 03. Jun, 2010 | 1 Comment

Microbiologically Induced Corrosion (MIC) occurs as both general corrosion and pitting corrosion, though localized pitting is the more definitive form and more likely to result in dramatic system failures. Low flow areas in circulating systems such as heat exchangers and process piping are particularly susceptible since these “stalled flow” locations provide bacteria with the opportunity [...]

Analyzing Material Fatigue

Posted by Rob in Failure Analysis on 04. May, 2010 | 4 Comments

A variety of analytical tools and techniques are used to identify fatigue fractures and their root cause. These include macroscopic examination, microstructural analysis, hardness testing, chemical analysis, microprobe chemical analysis and scanning electron microscopy (SEM). There are three stages in the life of a fatigue failure; 1. Initiation, 2. Crack Growth (propagation), and 3. Final [...]

The Service Environment

Posted by Rob in Failure Analysis on 04. May, 2010 | No Comments

Once a product leaves the factory you, the manufacturer, have lost control and all bets are off. Abuse and inadequate maintenance are leading sources of failure by fatigue, as well as other failure modes. Failure of components or assemblies “up stream” from your product may introduce higher loads than the product or component was designed [...]

Fatigue in the “Real World”

Posted by Rob in Failure Analysis on 27. Apr, 2010 | No Comments

In the “real world” fatigue usually – that’s usually, not always – initiates at a location that acts as a stress concentration, or focal point, to the stresses imposed on a component. Stress concentrations take a wide variety of forms. They include geometric features (such as holes, slots, corners and radii), rough areas of surface [...]