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Chromium (Cr) expansion coefficient

2003

Guillermo,

I am carrying out my master thesis about the oxidation at high temperatures of Cr. I have seen that you knew the expansion coefficient of Cr and its evolution when increasing temperature. Could you give more details about this subject? How is the plotting of the expansion coefficient in function of the temperature? Thank you very much.

Regards,

David Vilar Ferrenbach
- Barcelona, Catalonia, Spain

Let's see, you are going to take "information" from someone that you have zero idea of their competence. A Masters program in Spain must be a lot different than in the states. Why not a real reference, like the CRC Handbook of Chemistry & Physics [adv: on Amazon & AbeBooks & eBay] that has to be in every library in the world, Lange's Handbook of Chemistry [adv: on Amazon, AbeBooks, or eBay] or Perry's Chemical Engineers Handbook [adv: suggestions on Amazon, AbeBooks, or eBay] are just a couple of choices out of a bunch of possibilities.

James Watts
- Navarre, Florida
2003

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Jim, I think that schools in Spain aren't much different than in the States, but that schools today -- what with the internet --are different from schools of a couple of decades ago :-)

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003

Jim, thank you for your advices. But please, before judging something it has to be known well.

David Vilar Ferrenbach
- Barcelona, Catalonia, Spain
2003

David, point well taken. But, you did not ask where to find it, you asked for a answer - number (formula). I also assumed that you should be aware of it, as you could not get thru freshman physics or sophomore physics without using the chemistry and physics handbook. But then, that was a very long time ago.

James Watts
- Navarre, Florida
2003

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2003

To Ted and James,

Please don't rush to judgement. Mr. Vilar was referring to the following response to letter 15756 by Guillermo Marrufo, who has consistently given solid answers in this forum for years.

"++ Hard chromium thermal expansion coefficient is about 4 millionths per inch per Deg-F (7.4 microns per meter per °C) at room temp and increases with temperature (50% at 1,000 C). 17-4ph steel is slightly higher (around 5 english, 9 metric) Guillermo Marrufo Plating Mexico - Monterrey, NL Mexico"

Second, the coefficient of thermal expansion of Cr is not precisely known. It is not listed in Lange's Handbook of Chemistry (14th edn.), and other references differ:

CRC Handbook of Chemistry & Physics [adv: on Amazon & AbeBooks & eBay] (79th): 4.9 x 10(-6)/K (at 25C), ASM Metals Reference Book (3rd): 6.2 x 10(-6)/K (at 20C),

Chemical Engineers Handbook [adv: suggestions on Amazon, AbeBooks, or eBay] (7th) gives
6.8 x 10(-6)/K (20 to 100 C) and
8.6 x 10(-6)/K (20 to 500 C).

For experimental determination, use a high-temperature x-ray diffractometer (preferably with protective atmosphere). Perry's gives considerably more data for stainless steels, e.g., 18-8 has data from 325 F to 1500 F, of possible interest for an oxidation study.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.

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You're right, Ken.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003

No apology from me. Said what I meant and meant what I said. Part of a Masters degree is research. That is searching for the necessary data from the resources available. Being able to find available data is critical to most scientific fields. Also, since we do not know his application, what is the coefficient after it changes structure at ~600? Bet it is not the same.

James Watts
- Navarre, Florida
2003

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2003

David, found something useful. Perry's Chemical Engineersö Handbook, 7th Edn., Table 2-119. Has Cr densities from 50 to 1800 K. Easily converted to expansion data.

Mr. Watts, Cr(s) has a bcc crystal structure for the entire T range. There is a hiccupö in density near the Néel point (magnetic transition T) of 312.7 K, but overall the density decreases linearly with increasing temperature up to about 500 K, then roughly linear at a more rapid rate to 1400 K, then rather erratically up to 1800 K.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.

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2003

Dear David,

Assuming that you are interested in the thermal expansion coefficient for hard or functional chromium, it varies with the chemistry and deposition conditions. I am surprised that no one has mentioned an excellent reference, "The Properties of Electrodeposited Metals and Alloys" William H. Safranek. When I need data on electrodeposits this is the first book that I reach for. The data in this reference shows that the thermal expansion coefficient increases with increasing temperature ranges. Best regards,

Allen R. Jones
- Rock Hill, South Carolina