What testing methods are essential to ensure the quality and performance of fuel cell parts?

Non-Destructive Evaluation for Structural Integrity

Ensuring the quality of fuel cell components begins with non-destructive testing (NDT) to detect internal flaws without damaging the part. Methods such as X-ray radiography and ultrasonic inspection are essential for parts produced through vacuum investment casting and superalloy 3D printing. These techniques identify porosity, cracks, or inclusions that could compromise the sealing or mechanical performance of superalloy fuel cell parts. Advanced 3D scanning and computed tomography (CT) allow precise comparison of printed geometry with CAD models, ensuring dimensional accuracy across intricate internal channels.

Metallurgical and Microstructural Analysis

Fuel cell environments subject materials to extreme temperature gradients and corrosive conditions. Therefore, metallurgical analysis is critical for verifying that the microstructure meets design requirements. Processes such as material testing and analysis assess grain size, carbide distribution, and inclusion content. Superalloys like Inconel 625 and Hastelloy X must maintain a consistent γ′ phase distribution to ensure strength at elevated temperatures. Optical and scanning electron microscopy (SEM) are routinely used to confirm the success of post-processing steps such as heat treatment and hot isostatic pressing (HIP).

Mechanical Testing for High-Temperature Strength

To simulate service conditions, mechanical testing evaluates tensile, creep, and fatigue strength at operating temperatures often exceeding 800°C. Components such as separators and manifolds require stable performance under cyclic thermal and mechanical stress. Using alloys like CMSX-4 or Rene Alloys allows for benchmarking of yield strength and creep resistance. Fatigue testing under hydrogen exposure conditions helps assess crack propagation tendencies, ensuring long-term durability in fuel cell stacks.

Corrosion and Oxidation Resistance Testing

Given the hydrogen-rich and moist environment of fuel cells, corrosion and oxidation testing are vital. High-temperature oxidation tests and salt spray tests simulate the aggressive conditions experienced in the energy sector. Coated surfaces, particularly those with thermal barrier coatings (TBCs), are evaluated for adhesion, spallation, and diffusion resistance. Alloys like Inconel 939 are particularly tested for oxidation kinetics and phase stability, ensuring sustained conductivity and thermal reliability.

Dimensional and Surface Accuracy Inspection

After manufacturing and post-processing, dimensional control ensures that the complex geometries of flow channels, manifolds, and seals meet precise tolerances. Techniques like coordinate measuring machine (CMM) inspection and laser scanning validate critical surfaces processed through superalloy CNC machining and electrical discharge machining (EDM). These ensure that parts fit accurately within fuel cell assemblies and maintain consistent flow paths for gases and coolant.

In summary, ensuring the reliability of fuel cell components requires a multilayered testing approach that combines non-destructive, metallurgical, mechanical, and corrosion assessments to confirm the long-term stability and high performance of superalloy structures under extreme operational conditions.