Stainless Steel Testing Using Ultrasonic and Eddy Current NDT

Stainless steel is a widely popular material used in a range of industries including aviation, manufacturing, oil and gas, and more. Its corrosion-resistance properties and high strength make it a desirable material to work with even in a highly corrosive environment. The critical use of stainless-steel components in varying operations makes it mandatory to ensure that there are no flaws that can cause potential harm to the structural integrity of a component. This requires industries to leverage non-destructive testing (NDT) technologies during stainless steel testing.

The Need for Stainless Steel Testing

In a neutral and corrosive environment, stainless steel equipment is highly desired for its excellent properties. However, it is prone to flaws so it must be thoroughly inspected. Most of the flaws can be detected in the heat-affected zone around the welded joints. However, there can be metallurgical flaws in stainless steel resulting from inaccurate manufacturing parameters. During stainless steel testing, technicians can look for the possible presence of inclusions and cracks. It is also ideal to test for corrosion and thickness profile, especially in the heat-affected welded joints.

The Benefits of Using NDT for Stainless Steel Testing

NDT methods, ultrasonic testing (UT) and eddy current testing (ECT), are ideal for testing stainless steel structures and equipment to ensure their strength and integrity.

UT Inspection of Stainless Steel

In the welding process of stainless steel, factors like lack of proper surface preparation can increase the possibility of inclusions and resulting pores and cracks. Although the anisotropic coarse-grain structure of stainless steels and dissimilar metal welds can cause inspection challenges, using advanced UT techniques with innovative equipment can result in efficient, robust inspection procedures.

Ultrasonic testing involves a transducer emitting ultrasonic beams to the stainless-steel surface. The beams can be focused, and the amplitude of the reflected beam compared to identify the type, sizing, and location of the flaw. Phased-array ultrasonic testing (PAUT) with low-frequency 2D matrix array probes can be ideal to better navigate this challenge. The ability to vary frequency levels makes the inspection of components with varying wall thickness possible and the identification of a wide range of flaws easier.

 ECT Inspection of Stainless Steel

Eddy current testing can be useful in testing surface flaws like cracks in stainless steel tubes. An ECT probe induces an alternating current into the conductive stainless steel creating a field. Any change in the amplitude is an indication of potential flaws like cracks in the component.

With eddy current array (ECA) technology, the examination can be simplified. The ability to provide surface and near-surface inspection for a wide range of geometry also provides industries with the time-saving and cost-effective inspection opportunity.    

In corrosive or extreme temperature applications, where stainless steel components can be an important part, the strength and integrity of such equipment are crucial. The reliable testing ability of NDT methods like PAUT and ECA ensures the proper identification of stress cracking, corrosion, inclusions, and other types of degradation. The pre- and in-service inspection ability provided by innovative PAUT and ECA probes are advantageous for industries to ensure operational and employee safety.  

UT and ECT Solutions for Stainless Steel Testing

With stainless steel being used in different application areas, it is important for industries to recognize the potential problems that can be present in different stress or temperature limits. Especially in critical applications involving corrosive environments, where stainless steel is trusted for its mechanical properties, the need for flaw detection is even higher.

NDT technologies are now an integral part of industries responsible for ensuring the integrity of stainless steel components. In stainless steel testing, UT and ECT technologies can identify discontinuities that may impact structural integrity. The ability to identify a flaw allows industries to take proper action to ensure the safety and productivity of the operation.

Zetec, a leader in NDT technologies for over half a decade, is here to assist with your stainless steel testing needs, offering a wide range of eddy current and ultrasonic non-destructive testing technologies. To learn more, contact us today.