“Intermetallics in Duplex Steels can Seriously Reduce Their Integrity”
G2MT Labs offers fast, high-quality testing according to the ASTM A923 specification  to analyze intermetallics in duplex steel products that can seriously affect toughness and corrosion resistance.
Methods of Analysis Using ASTM A 923
The ASTM A 923 specification was developed for a specific wrought duplex (alloy S31803) but can be used for a variety of wrought and cast duplex stainless steels. ASTM A923 includes 3 different methods (A, B, and C):
ASTM A923 Samples by Method A Procedure:
Method A is the rapid screening method (“Sodium Hydroxide Etch Test for Classification of Etch Structures of Duplex Stainless Steels”), and is preferable for quick analysis of susceptibility to intermetallics in the microstructure. For Method A, the sample is polished and electrochemically etched in Sodium Hydroxide. Once etched, the microstructure is analyzed and separated into one of 4 groups:
• Unaffected Structure – This is what you want to see; the ferrite is etched without revealing any intermetallic phases, and the boundaries are smooth (as above).
• Possibly Affected Structure – Not preferable – in this case, the ferrite shows isolated areas of possible intermetallic phases and the interphase boundaries exhibit a slight waviness.
• Affected Structure – Not acceptable – the intermetallic phases are visible before or simultaneously with the ferrite phases when etch is applied.
• Centerline Structure – Not acceptable – this occurs when serious segregations occurs, such as when an intermetallic phase occurs in the mid-thickness area of sample, with or without affected structure outside of this area.
A923 Method B and C – To quantify the effects of intermetallic phases, additional tests by Method B, the “Charpy Impact Test for Classification of Structures of Duplex Stainless Steels” and Method C, the “Ferric Chloride Corrosion Test for Classification of Structures of Duplex Stainless Steels” are also offered. Contact our friendly sales team in Houston for more info on the right test for you.
Additional ASTM A923 Standard Resources
The ASTM A923 standard entitled “Standard Test Method for Detecting Detrimental Intermetallic Phase in Wrought Duplex Austenitic/Ferritic Stainless Steels”.