Salt Bath Nitrocarburise (Tufftride)
Salt bath Nitrocarburising is a thermo-chemical surface treatment carried out in molten salt at a temperature of 580oC. 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. TufftrideTM 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 580oC 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 580oC. 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
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
- Threaded components
- Molding tools
- Valve parts
- Hydraulic motor components