Institute of Fundamental Technological Research

This study investigates the use of high-frequency eddy current testing (ECT) to assess the structural integrity of aluminide coatings on MAR-M247 nickel superalloy under simulated fatigue conditions. Aluminide coatings, deposited via chemical vapor deposition at thicknesses of 20 µm and 40 µm, were tested using custom-designed probes optimized for defect detection. Results demonstrate that substrate grain structure and coating thickness significantly influence coating durability, with fine-grain substrates exhibiting the least resistance changes and greatest fatigue tolerance. Eddy current signal variations correlated with microstructural changes, enabling detection of damage otherwise invisible to traditional methods. These findings establish ECT as a precise, non-destructive approach for monitoring aluminide coatings in critical applications.

Nickel alloys, Aluminide coating, Non-destructive testing, Eddy current testing

In this paper, the effectiveness of the eddy current methodology for crack detection in MAR 247 nickel-based superalloy with aluminide coatings subjected to cyclic loading was investigated. The specimens were subjected to force-controlled fatigue tests under zero mean level, constant stress amplitude from 300 MPa to 600 MPa and a frequency of 20 Hz. During the fatigue, a particular level of damage was introduced into the material leading to the formation of microcracks. Subsequently, a new design of probe with a pot core was developed to limit magnetic flux leakage and directed it towards the surface under examination. The suitability of the new methodology was further confirmed as the specimens containing defects were successfully identified. The changes in probe resistance values registered for damaged specimens ranged approximately from 8 to 14%.

Nickel alloys, Aluminide coating, Non-destructive testing, Eddy current testing