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  1. Naruwan

    How detrimental is secondary austenite in Duplex Stainless Steel?

    Hi Guys, according to the details from the customer, the fillet metal is SANDVIK AWS ER2594 and the parent material is of ASTM A790 UNS S32760. The shielding/ purging gas is a mixture of 98%Argon+2%Nitrogen. Process is GTAW and position is 5G. Ferrite balance of these failed corrosion samples...
  2. Naruwan

    How detrimental is secondary austenite in Duplex Stainless Steel?

    Hi, I had been performing lots of ferrite count (in accordance to ASTM E562)on super/ duplex stainless steels. Besides ferrite count, we also had been performing ASTM G48 Method A pitting corrosion test on these stainless steels. Some specimens did failed the corrosion test. They normally...
  3. Naruwan

    Sigma stringers or delta ferrite stringers?

    Hi guys, I have a problem identifying the 'foreign' structure in this 316L heat affected zone. Attached is a photo-micrograph of a SS316L HAZ at 500X. I had used 10% Oxalic acid to etch the structure and found out there's strange structures which looked either like sigma phase or delta...
  4. Naruwan

    Ways to differentiate type of rust

    Hi guys, is there any way to determine the difference between Fe2+ and Fe3+? I don't think telling the difference by the colour of the rust will be reliable enough. In addition, had anyone heard of black rust from steel? They should be iron oxide which had been oxidized in a high temperature...
  5. Naruwan

    Component failed by fatigue?

    This is another matching surface, the shaft part.http://files.engineering.com/getfile.aspx?folder=a9e00d2f-e6c2-4be8-9780-b0044ce27fc4&file=IMG_0031.JPG
  6. Naruwan

    Component failed by fatigue?

    Hi Guys! one of our neighouring company passed this component to us and we are figuring what caused the failure. I reckon it was caused by fatigue, but not sure. This component seemed to have a flange like piece connect to a shaft. That's where it failed. It seemed that there are concentric...
  7. Naruwan

    Killed steel's grain size

    Dear all, I know that killed steel will need a content of Aluminum and Silicon as they are strong deoxidizers. a) Is there a different range (for these elements)for different grades of steel? b) Aluminum as a deoxidizer and for the control of grain size, then, how fine must the grain size be...
  8. Naruwan

    Shaft failed by torsion?

    Hi guys, I am back with some chemical and mechanical results. The chemical results are as follows: C:0.39%, P:0.007%, Sulphur:0.017%, Si: 0.26%, Cr: 0.95%, Mo: 0.18%. Mechanical results: UTS: 944 N/mm2 Yield stress: 563 N/mm2 Hardness (HRC): 287 averaged of three readings. It seemed that this...
  9. Naruwan

    Shaft failed by torsion?

    This is the same location taken at 500X.http://files.engineering.com/getfile.aspx?folder=e864dd2c-5f06-45f8-b85c-fc6f6599e86d&file=torsion_500X.txt
  10. Naruwan

    Shaft failed by torsion?

    Hi guys, I had did some SEM analysis on the failed hollow shaft especially on the torsion part. However, I am quite bewildered that they don't seemed to be microvoids which have been elongated in the direction of...
  11. Naruwan

    Questions regarding ASTM A90/ A 90M

    Hi guys, according to ASTM A90/ A 90M, nothing was mentioned about the removal of a paint coating before performing the stripping test as to determine the mass of coating on Iron or steel plates with metallic coating. Is paint removal a good media to remove the paint without jeopardizing the...
  12. Naruwan

    Shaft failed by torsion?

    Desertfox, so eventually, the shaft was failed by overloading. I was going to take some more photos (fractography) using SEM, checking it's chemical composition (They claimed that it's of AISI 4140), check on it's mechanical properties with impact test and tensile test. However I think there...
  13. Naruwan

    Shaft failed by torsion?

    A close up view of fractured surfacehttp://files.engineering.com/getfile.aspx?folder=1577f093-2118-44e7-a0ff-76b49d4195d7&file=IMG_1993.JPG
  14. Naruwan

    Shaft failed by torsion?

    End view of the shaft showing the fractured surface from another perspective.http://files.engineering.com/getfile.aspx?folder=39f56133-6767-4be6-ac5f-097bfa1594e8&file=IMG_1983.JPG
  15. Naruwan

    Shaft failed by torsion?

    A 'top' view of the broken shaft showing the fractured surface.http://files.engineering.com/getfile.aspx?folder=95ec70b4-7812-4f9c-9cfe-8e929781cbf6&file=IMG_1990.JPG
  16. Naruwan

    Shaft failed by torsion?

    This is another side view of the broken shaft.http://files.engineering.com/getfile.aspx?folder=3ba3e079-bf3c-456b-a4ba-ff0d02dc8ac9&file=IMG_1984.JPG
  17. Naruwan

    Shaft failed by torsion?

    Hi guys, I'm back with some more better photos. Apparently this hollow shaft was a part of a drilling equipment in a marine environment. The shaft had been in operation since the year 2005 under a seawater condition. The fracture surface is covered with brown rust and only a small portion...
  18. Naruwan

    Shaft failed by torsion?

    Hi guys, I just got this one and only photo from my client regarding a broken shaft. Based on this picture, I reckon it was failed by torsion. Of course I will be accessing this shaft tomorrow and hopefully will be getting more photos. Any comments? Thanks!
  19. Naruwan

    What structure is this?

    Dear all, i had etched a piece of annealed stainless steel 440C material with 10% Oxalic acid, however I can't identify any traces of martensitic structure. In addition, are the white islands carbide? I had attached a photomicrograph taken at 500X for viewing. Thanks!
  20. Naruwan

    Is this failure by shear or fatigue?

    Hi, dear all, this is a photo micrograph (at 100X) of the microstructure of the broken rudder stock which we are discussing earlier. You might be able to see that there are sulphide stringers embedded in the microstructure. The stringers aligned themselves in a way that they are along the...

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