Salt Bath Nitrocarburise (Tufftride)

Salt bath Nitrocarburising is a thermo-chemical surface treatment  carried out in molten salt at a temperature of 580^oC. The process is often followed by a further oxidation treatment in a caustic molten salt bath to give components the characteristic black finish which is also very corrosion resistant. Tufftride^TM is the trade name of Durferrit for their salt bath Nitrocarburising process.

Advantages & Properties

• Gives a very hard (800-1500Hv) wear resistant surface to the metal typically up to a depth of 0.002"(0.05mm) depending upon the material.
• The surface layer is in compression and so not conducive to crack initiation. This increases fatigue resistance
• As the process is carried out at 580^oC no phase changes take place as is the case with higher temperature treatments, and so there is little or no dimensional change in the components.
• When specified with the caustic molten salt quench the surface of the steel becomes very corrosion resistant. [Please reference the Durferrit website for further information]
• The hard wear resistant surface also exhibits self-lubricating & anti-seize properties.

Disadvantages and limitations

• The metal must withstand 580^oC. This is particularly important when previously heat treated components that are Tufftrided, as the temperature may lead to softening or distortion. (please ring for free advice)
• As the process is carried out in molten salt, removing this salt from deep small bore holes or hollow components can be difficult.
• Care must be taken with thin section components to ensure that the thin sections do not become Tufftrided all the way through & and hence become brittle.
• Tufftriding can reduce the corrosion resistance of stainless steels

Applications

Most engineering components that suffer from wear, corrosion, seizure or galling. Typical components would be:

• I.C. Engine crankshafts & camshafts
• Gas ram struts
• Hydraulic rams & pistons
• Steering & suspension components components
• Gears
• Threaded components
• Molding tools
• Valve parts
• Hydraulic motor components