ASTM A1084 Detecting Detrimental Phases in Lean Duplex Austenitic/ Ferritic Stainless Steels

Get Certified ASTM A1084 Detrimental Phase Testing

ASTM A1084 testing is used to determine if a certain low alloy duplex stainless steel contains phases that would adversely influence toughness and corrosion resistance. Technicians choose an appropriate specimen position and orientation and prepare specimens as outlined in the selected test method, conduct the test (examination or mechanical/corrosion tests as appropriate), and compare results with the requirements of ASTM A1084. Test Method A offers metallographic evidence and is a supplemental examination. Test Methods B and C outline how to perform tests for acceptance criteria in the standard. 

• Material: Austenitic/ferritic stainless steels selected for being lean. Purpose: The detection of harmful chromium-containing phases. 
• Typical Phases: Chromium-containing nitrides, carbides, and undesirable phases. 
• Test Methods: Etch examination, Charpy V-notch impact testing, and inhibited ferric chloride corrosion testing. 
• Temperature Sensitivity: Possible adverse phase formation temperatures of around 300°C to 955°C, with maximum sensitivity between 650°C and 750°C. 
• Evaluation: Identifies if any negative phase formation has occurred in sufficient amounts to be expected to affect the toughness or corrosion resistance. 
• Result: The result for the entire test is indicated by the appropriate procedure and acceptance criteria, as a pass or fail. 
• Product Forms: The standard addresses samples from coil, plate, sheet, tubing, piping, bar, and deformed bar, provided they are suitable for the method.
• Limitations: Tests are NOT necessarily the best indicator of the actual detrimental phase or toughness/corrosion loss due to other mechanisms. 

What are the uses of ASTM A1084 testing?

ASTM A1084 helps engineers determine whether thermal or fabrication histories have produced detrimental phases in selected lean duplex stainless steels. The results support material quality evaluation because conventional chemical and mechanical requirements alone do not necessarily demonstrate the absence of detrimental phases.  The testing helps with:

• Phase Detection: Identifies evidence of potentially detrimental phases. 
• Toughness Evaluation: Determines whether phase formation has adversely affected impact performance. 
• Corrosion Evaluation: Assesses corrosion behavior associated with detrimental phase formation. 
• Heat-Treatment Verification: Supports evaluation of appropriate heat treatment and cooling practices. 
• Material Comparison: Compares the performance of selected lean duplex stainless steel products. 
• Quality Control: Supports inspection of manufactured and fabricated stainless steel products. 
• Failure Investigation: Helps investigate unexpected reductions in toughness or corrosion resistance. 
• Material Selection: Provides information for applications requiring reliable duplex stainless steel performance. 

Which Materials Can Be Tested According to ASTM A1084?

ASTM A1084 applies to selected lean duplex stainless steel grades listed in the standard. The current edition lists UNS S32101, UNS S32304, UNS S32202, and UNS S82011.  The standard can be applied to:

• Lean Duplex Stainless Steel: Selected austenitic/ferritic grades covered by ASTM A1084. 
• Coil and Plate: Samples taken from coil and coil- or plate-mill products. 
• Sheet: Suitable sheet products can be evaluated using the applicable method. 
• Tubing and Piping: Test representative samples according to the applicable procedure. 
• Bar and Deformed Bar: Suitable bar products can undergo the specified evaluation. 
• Fabricated Products: Test Method C can be used to evaluate applicable fabricated products. 
• Base Metal: Sampling can focus on the appropriate base-metal location and orientation required by the selected method. 

Why is ASTM A1084 Testing Important?

Lean duplex stainless steels can develop detrimental chromium-containing phases when exposed to susceptible temperature ranges during manufacturing or fabrication. These phases can cause chromium depletion around the precipitates and reduce the material’s expected toughness and corrosion resistance. Proper heat treatment followed by sufficiently rapid cooling can reduce or eliminate these phases. ASTM A1084 provides standardized methods for detecting their harmful effects and helps engineers verify the condition of selected lean duplex stainless steels. 

ASTM A1084 Testing Process and Data Collection

Technicians determine the material grade, product form, sample location, and orientation. They fabricate test specimens using the chosen method and conduct the necessary examination, impact tests, or corrosion exposure. In Test Method A, metallographers analyze the etched metallographic structure for potentially undesirable phases. Because these phases can be very small, ASTM A1084 stresses the importance of careful metallographic examination. Technicians conduct the Charpy V-notch (CVN) impact test for Test Method B and report in Joules (J). Technicians immerse the specimen in the inhibited ferric chloride solution in Test Method C and determine the corrosion rate by measuring the weight loss, usually in mg/dm²/day (mdd). The final report lists the specimen identification, grade of material, test method, sampling site, dimensions of the specimen, test temperature, test results, observations, and the applicable pass/fail determination.

Common Challenges and Troubleshooting

ASTM A1084 results vary with specimen location, the material’s thermal history, surface preparation, specimen orientation, test temperature, and testing conditions. Metallographic preparation can make the appearance of detrimental phases difficult to observe, and the geometry of the specimen prepared may influence the results of the impact test or the temperature of the ferric chloride solution used in the test. To ensure reliable and comparable results, the technician should use the same specimen preparation method, calibrated equipment, test temperature and exposure conditions, and carefully follow the selected ASTM A1084 procedure.

• The report includes the metallographic analysis and observations made of potentially undesirable phases found in test method A. This approach is complementary and should not be considered as an acceptance/rejection criterion. 
• The laboratory measures Charpy impact energy in J and compares the obtained energy to the applicable acceptance requirement in test method B. In the standard, for instance, 70 J is specified for UNS S32101 and 100 J for UNS S32304 at room temperature. 
• In test method C, the laboratory data includes the mass of the specimen, specimen size, exposure conditions, and the computed corrosion rate (mdd). The maximum acceptable corrosion rate for the appropriate grades is 10 mdd at 25°C (77°F).
• Analysts document specimen identification, product form, sampling location, orientation, and relevant dimensions in mm. 
• The laboratory provides a pass/fail status report for the specified test method and acceptance criteria. 

Link to ASTM A1084