2x Chromium in A532 using PMI

[metalhoosier]

Why do I obtain readings from a calibrated portable alloy analyzer (Xray tube) of 45-58% Cr for A532 (28G) material which should be 23-30% Cr? Is it due to the volume of carbides on the surface of the cast impeller part between the interdedritic structure? I have no way of verify the microstructure currently so I'm taking a stab at it. Could someone please let me know if my thoughts are correct?

Thank you,
MetalHoo

 

[metengr]

What is your surface preparation procedure for PMI? Surface prep is critical for obtaining accurate results in addition to calibration. I have seen some very strange results by inexperienced PMI technicians in the field.

 

[arunmrao]

Is the carbon content range same in the standard samples used for calibration and the test sample? Surface preparation though contributes significantly to the accuracy of results.

Learn the rules,so you know how to break them properly.
Dalai Lama

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[metalhoosier]

metengr and arunmrao,

I think you hit the nail on the head. I ASSUMED the surface of this material was prepared as it is in an abrasive slurry bath, and was visually a white metal finish, however, I should have taken some sandpaper in with me during this inspection.

Won't make the mistake again!
Thank you,
Metalhoo

 

[arunmrao]

Why were you testing a used impeller? Any service life issues?

Learn the rules,so you know how to break them properly.
Dalai Lama

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