Cyaniding:

What is Cyaniding?

Cyaniding is a case hardening process where low-carbon steel or iron components are heated in a molten cyanide salt bath to absorb carbon and nitrogen, forming a hard, wear-resistant surface layer while keeping the core tough.

🔹 Why is it needed?

• Low-carbon steels lack hardness and wear resistance.

• Cyaniding forms a thin, hard outer layer (0.1–0.3mm deep) while keeping the core ductile.

• It enhances wear resistance and fatigue strength for small components.

How Does Cyaniding Work?

1. Immersion in Molten Cyanide Bath

• The component is immersed in a molten cyanide salt bath (800–950°C or 1470–1740°F).

• The cyanide bath contains sodium cyanide (NaCN) or potassium cyanide (KCN), which releases carbon and nitrogen atoms.

2. Carbon & Nitrogen Diffusion

• The carbon and nitrogen diffuse into the metal’s surface, forming a thin, hard case.

• The component is kept in the bath for 30 minutes to 2 hours, depending on the desired case depth.

3. Quenching & Hardening

• The part is removed and quenched in water or oil, locking in the martensitic structure for hardness.

• If needed, tempering is done to reduce brittleness and improve toughness.

Key Features of Cyaniding

✔ Very fast hardening process (compared to pack or gas carburizing).
✔ Thin case depth (0.1–0.3mm) – Ideal for small parts.
✔ Combination of carbon and nitrogen – Increases wear and fatigue resistance.
✔ Low distortion risk – Suitable for precision parts.

Advantages of Cyaniding

✅ Rapid process – Faster than other carburizing methods.
✅ High surface hardness – Improved wear resistance.
✅ Thin case with tough core – Ideal for small precision components.
✅ Better fatigue resistance – Increased lifespan under cyclic loading.
✅ More controlled than pack carburizing – Carbon and nitrogen absorption is uniform.

Disadvantages of Cyaniding

❌ Highly toxic process – Cyanide salts are hazardous and require strict safety measures.
❌ Environmental concerns – Waste disposal is difficult due to toxic chemicals.
❌ Limited case depth – Not suitable for deep hardening applications.
❌ Not suitable for large components – Mostly used for small parts.

Applications of Cyaniding

🔹 Automotive Industry – Gears, camshafts, crankshafts, fasteners.
🔹 Aerospace Industry – Small engine components, valve parts.
🔹 Manufacturing & Tools – Screws, nuts, bolts, cutting tools.
🔹 Firearms & Defense – Small firearm components, precision parts.