DOI: 10.4028/www.scientific.net/MSF.730-732.733

https://www.jstage.jst.go.jp/article/isijinternational/52/6/52_1054/_pdf

It is possible by measuring the XRD peak Fe_gamma/Fe_alfa intensity ratio or using a magnetic ferritometer, also metallographic intercept lines method

In case of 17-4PH which is precipitation hardenable martensitic steel DELTA FERRITE can not be checked by FERRITO-SCOPE (Used only for austenitic stainless steels)

In this case you can check and quantify % delta ferrite by optical microscope having image analyser software for phase analysis.Delta ferrite appears mostly as thin and thick long stringers in base structure of martensite

As far as accuracy of results is concerned 17-4PH may have some amount of retained austenite if not cooled below its Mf temperature (32 deg.C) and can have some effect on result but one can easily differentiate the two and accordingly adjust gray scale threshold.

Regarding quantification by XRD , it is possile only to show peaks of Delta ferrite and austenite and not % in bulk sample

Best will be to give your sample to any metallurgical test laboratory or else you can send sample to me , I shall do it for you on microscope in my metallography lab.

SHIVRAJ SINGH KASANA

Delta ferrite can be selectively etch and measured by image analysis. See attached.

Dear George Frederic Vander Voort ,

What etchants do you recommend to use in order to show the prior austenite grain boundaries after I have measured ferrite content?

Thank you in advance.

Spyridon:

In a heat treated steel, you can only reveal PAGBs when the structure is martensite or lower bainite. You cannot reveal PAGBs in ferrite, pearlite or upper bainite. It used to be that the steel had to have a C content of 0.35 wt. % or higher and it could not be done if the steel was tempered above ~1070 F. P segregates to the PAGBs so if the steel had a low P content, below ~0.02%, it would be very difficult to reveal PAGBs. In some steels, a second phase/constituent can be precipitated on the PAGBs allowing an estimate to be made of the PA grain size. This is a difficult and frustrating task for a metallographer!

George

We are using the Murakami etchant (60°C; 6 minutes) and image analysis to determine the delta ferrite portion.