Duplex and Intermetallics
Duplex and Intermetallics
(OP)
Hello all,
Duplex and super duplex grades are prone for the forming of intermetallic phases that lower corrosion resistance and mechanical properties like impact strength.
These phases grow in a temperature range between 950-600 degC during heat treatment and/or welding. After metal fabrication rapid quenching is needed after solution annealing to avoid intermetallics to grow and to get the correct phase balance.
Now I am wondering which phase fraction of intermetallics like Sigma, Chi and Laves is still acceptable in base materials (plates or forgings)?
In large object forgings intermetallics cannot be avoided completely but what is the amount that still can be accepted? What phase fraction do I have to think of 0,5, 1, 2%? Already knowing this is strongly related to the corrosion & mechanical test results but in order of magnitude!
Kindest regards,
Euroweld
Duplex and super duplex grades are prone for the forming of intermetallic phases that lower corrosion resistance and mechanical properties like impact strength.
These phases grow in a temperature range between 950-600 degC during heat treatment and/or welding. After metal fabrication rapid quenching is needed after solution annealing to avoid intermetallics to grow and to get the correct phase balance.
Now I am wondering which phase fraction of intermetallics like Sigma, Chi and Laves is still acceptable in base materials (plates or forgings)?
In large object forgings intermetallics cannot be avoided completely but what is the amount that still can be accepted? What phase fraction do I have to think of 0,5, 1, 2%? Already knowing this is strongly related to the corrosion & mechanical test results but in order of magnitude!
Kindest regards,
Euroweld





RE: Duplex and Intermetallics
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: Duplex and Intermetallics
I h ave been involved in a couple of cases where the original plate was clean, but welds did not perform well.
We discovered that even though there were not secondary phases in the plate there was still significant segregation that made the re-precipitation of intermetallics much faster than would be expected.
Finding some of these intermetallics by micrography is very difficult, such as with alpha phase.
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Plymouth Tube
RE: Duplex and Intermetallics
RE: Duplex and Intermetallics
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Plymouth Tube
RE: Duplex and Intermetallics
RE: Duplex and Intermetallics
This is to reveal any intermetallics that may have been removed from the original surface by processing or treatment.
No chemical treatment of the test samples is allowed.
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Plymouth Tube
RE: Duplex and Intermetallics
Thanks for all answers!
When we talk about corrosion testing do we mean a ferric chloride corrosion test like ASTM A923 method C? Does this also mean that method C of ASTM A923 is more usefull than method B for detecting intermetallics?
I am curious about the fraction that is still allowable for dss! Is this a volume fraction of 0,5, 1, 2%. For instance: what is the reduction of toughness and corrosion resistance with a volume fraction of about 1%? I am not looking for accurate numbers but just an impression based on expierence. I am aware that this a very complex matter but in order of magnitude.
Besides that:
At this moment it seems that the thickness for large dss objects is limited because of the cooling rate of the core from the object during quenching. In the market the limit seems to be somewhere around 250mm. Is this true and are there any developments regarding this topic?
RE: Duplex and Intermetallics
It depends on the specific alloy, and the quench method.
Some people have moved to chilled water for quench just to get a little more advantage.
C2014-3651 Francis and Hebdon
200mm bar is pushing the limits, if you have a casting or forging that has holes in it then maybe you can get to 300mm.
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Plymouth Tube
RE: Duplex and Intermetallics
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.