White Layer in Plasma Nitriding: What It Is and Why It Matters

Microhardness profile of a plasma-nitrided component. The image highlights the white layer and diffusion zone, with Vickers indents marking hardness measurements at different depths.

White layer is the outermost layer, with a maximum thickness of 25 micrometers (0.025 microns), rich in iron nitrides (Fe₄N and Fe₃N). It is characterized by:

• High surface hardness: Significantly higher than the core material.

• Wear resistance: Excellent resistance to abrasive and adhesive wear, especially the latter.

• Potential brittleness: It may be more brittle compared to the diffusion zone.

Beneath the White Layer, there's a layer up to 0.7 mm thick, known as the Diffusion Zone, characterized by the presence of nitrogen diffused into the metallic matrix.

• Maintains the hardness of the base material with improved wear characteristics.

• Hardness decreases gradually from the white layer to the core.

• Fatigue resistance: Enhanced due to the compressive stresses induced by nitrogen.

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📊 Download infographic: Unveiling the Compound Zone (White Layer)

https://www.ionheat.com/plasma-nitriding-fundamentals-1/unveiling-the-compound-zone-(white-layer)

📊 Related resource: Reactions that occur at the surface of the part during Plasma Nitriding

https://www.ionheat.com/plasma-nitriding-fundamentals-1/reactions-that-occur-at-the-surface-of-the-part-during-plasma-nitriding 

📊 Related resource: White Layer, asset or liability?

https://www.ionheat.com/plasma-nitriding-fundamentals-1/white-layer%2C-asset-or-liability%3F