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Thu Aug 25, 2016, 01:21 AM

Superalloy Failure Apparently Had "Painful" Results in the Vietnam War.

Last edited Thu Aug 25, 2016, 08:08 AM - Edit history (1)

I've been leafing through an interesting monograph on Materials Science, specifically "superalloys" with which I've been hanging out for the last few years. Here is a link to the monograph:

Superalloys Alloying and Performance

"Superalloys" are alloys, generally nickel based, that show high mechanical strength at high temperature while being resistant to corrosion (oxidation). They hold an extremely important role in modern technology for use in things like jet engines and power plants operating at high efficiency.

I wrote a riff citing this book elsewhere:

Technetium: Dangerous Nuclear Energy Waste or Essential Strategic Resource?

Anyway, I came across this interesting bit in the text about the failure of superalloys during the Vietnam war, which apparently had some unfortunate consequences:

Other superalloy derivatives, such as oxide-dispersion-strengthened(ODS) alloys and mechanically alloyed alloys, were developed at Dupontin 1965 and INCO in 1966, respectively. Later, starting in 1969, Pratt and Whitney Aircraft pioneered an entirely new field with the development of directionally solidified alloys for airfoils (Ref 7).While the vacuum casting processes had opened the door to higher levels of alloying, the precipitation of detrimental phases and the subsequent loss of properties in superalloys during service revealed the need for compositional limits based on phase stability that were largely independent of the manufacturing process. The formation of detrimental phases was found to be associated with high chromium levels, which prompted a reduction of chromium levels in superalloys from approximately 20 to 10 weight percent. The reduction in chromium made the alloys vulnerable to hot corrosion, which was painfully evident in helicopter engines ingesting seaspray during the Vietnam War. Although chromium levels could not be increased without loss of mechanical properties, the environmental resistance of the low-chromium alloys was clearly unacceptable.


Um, the Vietnam war itself was "clearly unacceptable," but no matter...

This tidbit is found on page 5 of the text.

That's an interesting bit of history about which I never heard, and I thought other people might find this obscure fact interesting, so I'm posting it.

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Reply Superalloy Failure Apparently Had "Painful" Results in the Vietnam War. (Original post)
NNadir Aug 2016 OP
CentralMass Aug 2016 #1
NNadir Aug 2016 #2
CentralMass Aug 2016 #3
NNadir Aug 2016 #4

Response to NNadir (Original post)

Thu Aug 25, 2016, 02:17 AM

1. Thank you for posting..I find it to be very interesting

I also really enjoyed the material science class that I took in college.

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Response to CentralMass (Reply #1)

Fri Aug 26, 2016, 12:09 AM

2. My pleasure. What was your major that lead you to take this course?

I'm something of an autodidact where materials science is concerned, but I'm being lead by my son, a high school senior to be, who is looking to attend a university with a materials science major.

It's interesting that not every university actually offers that major to undergraduates and those that do stick in different places, usually engineering, but sometimes in chemistry or physics departments. Because not many people seem to be interested in the topic, the student to professor ratios tend to be excellent.

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Response to NNadir (Reply #2)

Fri Aug 26, 2016, 02:53 AM

3. I took the class at Northeastern University in Boston as elective to finish up with a CS degree.

At the time I was doing some R&D work involving specialized high speed probe interfaces used in the semiconductor testing industry that used a variety of interesting materials like polyimide membrane circuit boards with contacts made of alloys like copper beryllium and some other materials used in the force delivery mechanisms in the interfaces. The class was very usefully in helping me understand the materials that I was working with.

In the application the probes were contacting aluminum contact pads with sufficient enough force to break through an aluminum oxide layer on the surface of the pad so that the probes would achieve adequate electrical contact resistance between probe and pad. I developed automated life cycle testing techniques that allowed Kelvin contact resistance measurement to be made over time.
Over time the probe tips would accumulate aluminium + aluminum oxide residue that would degrade the contact resistance. So I had to develop cleaning techniques to remove the contaminants using an online automated abrasive cleaning process and some offline chemical cleaning processes.

The class gave me a better understanding of the properties of the materials I was using and why they were being used. It covered metals, alloys, eutectic alloys, polymers etc.

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Response to CentralMass (Reply #3)

Sat Aug 27, 2016, 05:01 AM

4. That sounds like very fun work. I am merely a CS dilettante, but I did notice...

...that the upcoming Wolfram Technology Conference will have a section focusing on solid printing.

My kid and I have been playing with Mathematica/Wolfram Language stuff; it's amazing; it will go up to the internet and pull out physical constants if you just type the name.

Hopefully you didn't have to play around with too much beryllium. It's a wonderful element in many ways, but frankly, it's one with which I'd never want to play much, and I'm a guy who used to handle five liter flasks of pure liquefied phosgene.

I know lots of people who want to fill huge nuclear reactors with beryllium fluoride, but as much as I like nuclear reactors, I'm not one of them. There are better eutectics than Flibe.

It sounds, happily, that you were working with tiny amounts on circuit boards. (It's amazing how much toxic stuff is in circuit boards and other electronic devices like, for example, solar cells.)

Thanks for appreciating a science outside of your specialty. That's exactly what the world needs its scientists to do; but of course, much to our benefit, that's what many of us do.

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