Salt Bath Nitrocarburising: Process, Benefits & Uses

What is Salt Bath Nitrocarburising?
Salt bath Nitrocarburising is a thermo-chemical surface treatment performed in molten salt at a temperature of 580°C. This process is often followed by an oxidation treatment in a caustic molten salt bath, providing components with a distinctive black finish that enhances corrosion resistance. Tufftride™ is Durferrit’s trademark for their salt bath Nitrocarburising process.

Benefits and Properties

  1. Enhanced Wear Resistance:
    Provides a hard surface (800-1500 Hv) up to a depth of 0.002″ (0.05mm), increasing durability.
  2. Increased Fatigue Resistance:
    The surface layer is in compression, reducing crack initiation and boosting fatigue resistance.
  3. Minimal Dimensional Change:
    Conducted at 580°C, this treatment avoids phase changes, ensuring minimal or no dimensional distortion.
  4. Corrosion Resistance:
    When combined with a caustic molten salt quench, the surface gains excellent corrosion resistance.
  5. Self-Lubricating and Anti-Seize Properties:
    The wear-resistant surface exhibits self-lubricating and anti-seize characteristics, reducing friction and wear.

Disadvantages and Limitations

  1. Temperature Sensitivity:
    Components must withstand 580°C. Previously heat-treated parts may soften or distort during the Tufftriding process.
  2. Salt Removal Issues:
    The molten salt used in the process can be challenging to remove from deep holes or hollow components.
  3. Thin Section Considerations:
    Care must be taken with thin-section components to prevent brittleness from excessive Tufftriding.
  4. Impact on Stainless Steels:
    Tufftriding may reduce the corrosion resistance of stainless steel components.

Applications of Salt Bath Nitrocarburising

Salt bath Nitrocarburising is ideal for components that endure wear, corrosion, seizure, or galling. Common applications include:

  • I.C. Engine Crankshafts & Camshafts
  • Gas Ram Struts
  • Hydraulic Rams & Pistons
  • Steering & Suspension Components
  • Gears
  • Threaded Components
  • Molding Tools
  • Valve Parts
  • Hydraulic Motor Components

Salt bath Nitrocarburising, especially with the Tufftride™ process, provides durable, wear-resistant, and corrosion-resistant surfaces, making it suitable for a wide range of engineering applications.