Duplex Stainless Steel

The first step towards effective inspection is chemical composition analysis, allowing the technician to assess whether the metal meets the standard. Many downstream issues can be anticipated in this step.

Macroscopic Inspection involves using the naked eye or a magnifying glass no greater than x10 to identify defects. This is an essential early step that can guide subsequent inspection and testing. This will immediately locate more obvious pitting corrosion.

Moving to more intensive analysis, Metallographic Structure Inspection looks at the internal structure of the steel and pinpoints defects. It can determine grain size, inspect inclusions, inspect depth of decarburization layer, and the segregation of chemical composition.

Testing of hardness is an important next step. The two most common approaches are the Brinell and Rockwell methods, but the Vickers, Shore, and microhardness methods are also effective.

Tensile testing measures both the strength index and plastic index of the metal. This is an essential step to match the material with the design and engineering needs. At normal temperature, strength indicators include yield point and tensile strength. At high temperatures, strength indicators include creep strength, enduring strength, high temp. specified non-proportional elongation stress.

Impact testing measures the materials ability to absorb impact energy - the higher the absorbed energy, the higher the resistance.

Non-destructive testing (NDT) includes other methods that can be utilized without requiring down-time. Ultrasonic testing (UT) involves a transducer emitting ultrasonic beams to the metal surface. The amplitude of the reflected beam is then compared to identify the type, sizing, and location of the flaw. 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. Eddy Current Array (ECA) technology can pinpoint underlying defects, which might have gone unnoticed with other non-destructive testing methods, including minuscule stress points that are harder to read. ECA testing can ensure the proper identification of stress cracking, corrosion, inclusions, and other types of degradation.