CU5MCuC tensile & eleongation failure..

[RAJMETALLURGY]

Inconel 825 (CU5MCuC), tensile & elongation is getting failed after solution annealing & stabilizing treatment. I have tried with only solution annealing treatment but that too getting failed but as per standard A494 we have to do solution annealing & stabilizing. The fracture surface doesnt look like cup and cone fracture.

Kindly help me to come out from this.

 

[EdStainless]

Is this the cast material?
Are you getting good enough homogenization?
You need to do some micros and look carefully at grain boundaries.

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Plymouth Tube

 

[RAJMETALLURGY]

I have attached the micro-structure of the material (100X) with 10% Oxalic acid as a etchant. Any suggestion on this.

 

[RAJMETALLURGY]

yea this is a cast material

 

[metengr]

First, have you performed an examination of the fracture surface to determine if the brittle fracture was intergranular using an SEM? Next evaluate the grain boundaries to determine if segregation is occurring to cause the intergranular fracture. Metallographic examination is only part of solving the problem.

 

[RAJMETALLURGY]

I have sent the samples for SEM & EDAX analysis already. If there is a segregation how can we avoid the same. By heat treatment how can we avoid that.

 

[metengr]

The segregation can be of contaminants. See what the results show before you decide on what to do.

 

[EdStainless]

I don't like the micro.
What anneal did you use?
I don't see grain boundaries (etch more?).
But I see a lot of trash, that didn't go into solution in anneal.

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Plymouth Tube

 

[Guest102023]

You're right, Ed, I don't like the looks of that micro either.
Solution anneal is called for, although chemistry should probably be verified first.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[RAJMETALLURGY]

I have attached another microstructure and chemistry below

C: 0.021%
Mn: 0.75%
Si: 0.79%
P: 0.017%
S: 0.002%
Cu: 1.82%
Ni: 39.51%
Cr: 19.9%
Mo: 2.86%
Nb: 0.801%
V: 0.037%
W: 0.104%
Fe: 32.90%
Co: 0.401%

 

[metengr]

What did the SEM/EDAX results of the brittle fracture show? You have V,W and Co in amounts which are excessive. Seems like the scrap used to make this heat of cast 825 might be the issue.

 

[EdStainless]

The W is the most troubling.
Looking at the micro I see a haze along the grain boundaries, this is not good.
This is a stabilized alloy, so there should be a uniform distribution of NbCN particles throughout the structure.
It looks like a secondary phase formed on solidification (perhaps a W rich one) that you didn't dissolve in the anneal.
Try to reanneal a sample. Use 100F hotter ( at least 2100F) for 6 hours and water quench. You should be able to get a better microstructure.

Materials Scientists think that microstructure determines properties, Materials Engineers know that defects determine properties.

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Plymouth Tube

 

[RAJMETALLURGY]

Mechanical properties were Ok in few heats with the same above chemical composition (W: 0.104%). Heat treatment was carried out @ 1190 Deg C for 3 hours (soaking based on the thickness) and stabilizing carried out @ 960 Deg C and 4 hours.

Is there anything I can do with heat treatment to modify the mechanical properties.