Eddy Current Testing (ET) Services for Forgings | Fast Surface & Sorting NDT | Shivam Forge

Inspection Through Induced Current, Not Sound or Radiation

Among the standard NDT methods applied to forged and bar stock components, eddy current testing occupies a genuinely distinct position because of the physical principle it relies on: rather than sound waves, radiation, or a magnetic particle medium, ET induces electrical eddy currents directly in the test material using an alternating-current coil, and reads discontinuities and material property variations through the resulting change in the coil's electrical impedance. This electromagnetic mechanism only works on electrically conductive materials — which conveniently includes essentially all metals, both ferromagnetic and non-ferromagnetic — and it produces its result as an instrument-measured electrical signal rather than a visual indication or an image, a difference that shapes exactly where and how ET gets deployed relative to other NDT methods.

The practical mechanism worth understanding is the 'skin effect': induced eddy currents concentrate near the material's surface and decay in intensity with depth, which is precisely why ET is fundamentally a surface and near-surface inspection method rather than a volumetric one like UT or RT. Surface-breaking or near-surface discontinuities — cracks, seams from the original bar rolling process, laps from forging — disrupt the local eddy current flow in a way the coil detects as an impedance change, giving ET strong sensitivity to exactly the discontinuity types most likely to originate at a bar's rolled surface or a forging's as-formed surface. This same electromagnetic sensitivity extends to a genuinely separate application: because electrical conductivity itself varies measurably with alloy composition and with a material's heat treatment condition, eddy current instruments can be used for conductivity-based sorting and screening, distinct from — though using the same underlying physics as — flaw detection.

Eddy current testing's defining practical advantage over other surface-inspection methods is speed combined with a complete absence of consumables: no couplant gel the way UT requires, no penetrant/developer process time the way PT requires, no magnetic powder or subsequent demagnetization the way MPI requires. This makes ET the natural choice for high-speed, automated, in-line inspection scenarios — bar stock and tubing scanned continuously as it moves through a production line, for instance — where any of those other methods' setup or process time would create an unacceptable throughput bottleneck. The tradeoff is ET's inherent limitation to surface and near-surface coverage and its greater sensitivity to part geometry and probe lift-off variation, meaning it complements rather than replaces volumetric methods like UT and RT for internal soundness verification.

For manufacturers requiring rapid, automation-compatible surface inspection of bar stock, tubing, or finished forged component surfaces, or conductivity-based alloy sorting and verification, Shivam Forge provides eddy current testing per ASTM E426/E243 with full documentation. Contact our quality engineering team at +91-9265772827 or sales@shivamforge.com with your component and inspection scope requirement to discuss quotation.