ASTM A923 Detecting Detrimental Intermetallic Phase in Steels

ASTM A923 Introduction

ASTM A923 establishes a standardized approach to assess the susceptibility of duplex austenitic/ferritic stainless steels to detrimental intermetallic phase formation. Intermetallic phases, such as sigma (σ), chi (χ), and others, form during the heat treatment or welding of these steels. The test method helps to detect, characterize, and quantify the presence of these phases. Three test methods are described in the ASTM A923 standard to classify duplex stainless steel structures: sodium hydroxide etch test, Charpy impact test, and ferric chloride corrosion test.

ASTM A923 Test Method

The ASTM A923 test method involves the macroscopic examination of specimens to observe the presence of intermetallic phases. The size, distribution, and morphology of the intermetallic phases are assessed. The test is conducted using the following steps:

To classify duplex stainless steel structures, there are three test methods described in ASTM A923. Test Method A—Sodium Hydroxide Etch Test for Classification of Etch Structures of Duplex Stainless Steels (Sections 3 – 7). Test Method B—Charpy Impact Test for Classification of Structures of Duplex Stainless Steels (Sections 8 – 13). Test Method C—Ferric Chloride Corrosion Test for Classification of Structures of Duplex Stainless Steels (Sections 14 – 20).

ASTM A923 Equipment and Sample Preparation

ASTM A923 Results and Interpretation

The test method ASTM A923 provides criteria for evaluating the presence and severity of intermetallic phases in duplex austenitic/ferritic stainless steels. The Ferric Sulfate-Sulfuric Acid Test (FISCH) provides a qualitative assessment of intermetallic phase formation. The Charpy impact test provides quantitative data on the material’s impact toughness, which can be affected by the presence of intermetallic phases.

Tests Related to ASTM A923

The ASTM A923 test method is related to ASTM E45, a standard test method for determining the inclusion content of steel. It offers methods for determining the presence and size of inclusions in steel, which is a related standard. ASTM A923 is also related to ASTM A370 for the determination of mechanical testing of steel products.

Use of ASTM A923 in Various Industries

It serves as a crucial tool in the aerospace, oil and gas, chemical processing, and power generation industries because it provides for methods of tests used to evaluate the susceptibility of duplex stainless steels to intermetallic phase formation; material reliability is ensured, and all hazards, from premature failure through to environmental damage, are avoided.

Materials Commonly Tested with ASTM A923

This test applies to duplex and super duplex stainless steels suitable for chemical, marine, and oil applications due to their resistance against corrosion and satisfactory mechanical properties. The test usually assesses undesirable phases that may jeopardise the material’s durability and performance.

Common Challenges and Troubleshooting in ASTM A923 Testing

With this method of testing, determination of properties in intermetallic phases poses a challenge to steel properties. In many cases, results fail to yield the right answer due to various conditions and material preparation, besides operator skill levels. Troubleshooting includes the calibration of the equipment plus heat treatments and sample homogeneity.

Safety and Best Practices in ASTM A923 Testing

Standard testing safety involves wearing personal protective equipment, using standardized procedures with calibrated instruments and having material handling procedures in place for safety and accuracy of results.

Importance of ASTM A923

This standard provides quality and reliability for duplex stainless steel in demanding environments; it detects damaging intermetallic phases, hence making the industry save costly failures with improved performance, further saving lives and improving efficiency in the high-performance alloy industries.