NDT portable Device to measure the amount of Sigma Phase ?

[stanislasdz]

Hi everybody

I am looking for a NDT portable device to measure the Sigma Phase on a part made by an 310 AISI steel

Can anyone help

Thanks

 

[JoeyV87]

I can't imagine how such a device would work, and I have never heard of one existing. Indirectly you could use a ferritector or permeablity meter, but the accuracy wouldn't be guaranteed.

 

[unclesyd]

I've used two different meters specifically made for measuring Ferrite in SS. They were a Magna-Gauge and one made by Elcometer. I can't recall the expected accuracy but many a piece of 316 and 310 SS were removed from service due to numbers produced by these meters.

In every case the presence of Sigma was verified by Metallurgical analysis.

 

[Guest102023]

unclesyd, how would that work, because (correct me if I am wrong) sigma is not ferromagnetic?

 

[unclesyd]

You are most correct. Must have been the fog in the windmills. Sorry I mislead you. other areas we did boat the areas in question.

You are forcing to to go way back (the late 50's) in time for this one. These measurements were made on the outlet manifolding on two stream methane reformers and some piping on a very large submerged combustion system. The H2 plant materials were HK40 tubes with 310HC SS manifolds and 316 SS laterals on the manifolds. All these welds carried a lot of Ferrite in the welds due to the inadequacy of the welding electrodes. I can't recall the numbers but they were very high and evidently the welds had been mapped as built(1952) and we measuring the loss of ferrite due to conversion of the ferrite to Sigma Phase. As I piece the process back together I think we may have been looking for low ferrite numbers. I can't get any verification of this as I'm about the only one left around. A I've stated before the rag pickers have got rid of all the old records and reports.

The submerged combustion unit had two problems, nitriding and Sigma Phase. It was all 316 SS welded by SMAW with very heavy welds due to the configuration.

 

[Guest102023]

Aha, now I know it is welds, then magnetic methods make perfect sense. I prefer the Fischer Ferritscope.

 

[stanislasdz]

Thanks everybody

My problem is to find a device to measure the amount of the sigma phase.

In fact we use an AISI 310 parts in our heat treatment shop and these parts break after a certain time due to the sigma phase precipitation.

I ma tying to optimise the chemical composition

But for the parts we have now in service we want to know the mount of the sigma phase with non destructive method.

The only non destructive method I found is to check the hardness with a portable device EQUOTYP because the safe part show à low hardness 170 HB and the broken parts show a high hardness 240-250 HB

 

[arunmrao]

Check the carbon in 310 parts,if it is high it can break easily. Also are the parts used in carburizing atmosphere or are they used for oil quenching . If yes,then again these parts have a short life. Try and change the grade of fixture material.

 

[0707]

I do not know of any portable devices to measure sigma phases. We have check it in the past only in laboratory with a ndt to check the volumic percentage.

luis

 

[rustbuster]

We use insitu metallography (replicas) to look for Sigma as well as other microstructural phenomina.