Retained Austenite
Retained Austenite
(OP)
Does anyone know what the best method would be for detecting retained austenite on 440c? Any images or information is appreciated.
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RE: Retained Austenite
RE: Retained Austenite
http:/
RE: Retained Austenite
RE: Retained Austenite
TVP - The link didnt seem to produce an article on this topic. I am very interested to see what it was. If you know of another working link please let me know. I was hoping to find more information on what types of etchant would produce a good visual.
As of now I have only used Fry's etchant. Is there anything that would be more suitable for use on a polished cross section?
Why is it that when testing hardness on rockwell vs micro, the numbers do not seem to comapare like they do on other types of steel?
RE: Retained Austenite
Back in the 1970's, I remember seeing some research that attempted to correlate difference between Rockwell 'C' hardness and converted Vickers hardnesses to the amount of retained austenite. I don't know what the results of this research (it was way too long ago and I have not had any need for the past 20 years or son), but I'd bet a bit of research would find some Master's theses or PhD dissertations on the subject.
rp
RE: Retained Austenite
If uncertain what you have , you can test some grains with micro hardness; You won't get bulk hardness resulte but you can identify austenite vs carbide grains.
RE: Retained Austenite
RE: Retained Austenite
I clicked on the link again, and it works. The article title is "Hints for Imaging Phases in Steels", with the discussion on Analyzing Austenite beginning on page 4 of the .pdf (page 35 of the original article). Figure 10 shows Type 440C stainless etched with Beraha's sulfamic acid no. 4 etch, revealing retained austenite. The article gives the composition of the etchant and how to use it.
RE: Retained Austenite
RE: Retained Austenite
Many thanks for the clarification.
chr1000,
I apologize for the confusion. Apparently I have all of the cookies, etc. turned on in Internet Explorer that allows direct navigation to the articles. Anyway, the following are two links to George Vander Voort's personal website, one for the article I mentioned previously (Imaging of Phases in Steels from Feb 2005 issue of Advanced Materials & Processes) and one for a related article that appeared in the Apr 2009 issue of Industrial Heating:
Imaging of Phases in Steels
http:
Martensite and Retained Austenite
http://ww
RE: Retained Austenite
It is also possible to do growth calculations before and after an additional temper. Internally we use an additional temper of 220°C for 6 hours, with a growth of 10 microns per 100 mm diameter is equivalent to 1% RA for rings (52100 material). Allow 24-48 hours before re-measurement. As when the austenite is transformed in martensite and volume increase occurs.
Typically 440C has a 6-8% of stable retained austenite due to the high levels of carbon and chromium.
I have a question related to transformation of retained austenite:
If 440C material undergoes an additional temper (150-200°C), after hardening, quenching and tempering cycles (including a deep freeze), why does the material shrink afterwards? Typically having a RA value in region of 6-12%.
If the retained austenite is transformed persumably into martensite, it should grow. Is the martensite temperature not being reached? Therefore changing the austenite into ferrite and cementite (not ever changing to martensite)?
Thanks Ian
Metallurgist, Plymouth.
RE: Retained Austenite
Amourian, can you provide some data for review to help in the analysis of your problem?
Maui
www.EngineeringMetallurgy.com
RE: Retained Austenite
amourian78,
While I can't answer your question as to why you see shrinkage during heat treatment of your 440C races, I can confirm that the slight, controlled dimensional growth produced by the austenite/martensite transformation during quenching is of great interest with steel bearing races, especially large diameter ones. Large diameter, thin section bearing races are quenched using close fitting internal quench rings to help keep them round. The close fit of the internal quench ring fixture relies on the slight dimensional growth of the race during quenching to ensure that it pops free after quenching.
terry