Nitriding

With this procedute the surface hardness(https://plastic-mold.net/hardness-conversion-chart.html) of steel can be increased by the formation of itom nitrides in the surface. The part is heated in a nitrogen-rich environment, usually a gas (ammonia) or a powder bath (the Tenifer process). The Tenifer process is normally preferred as the process time is much shorter (3-5 hours) than for the gas method (up to 100 hours), Nitriding has several advantages over carburising as follows: Most alloy tool steels can be used, apart from stainless steel. There is less risk of distortion as lower temperatures are used. Hardness is maintained at high temperatures, which is very useful for hot runner manifolds, nozzle blocks, cylinders and cylinder screws, This process will yield hardnesses up to 70 Rc with the surface having a very brittle layer. This means that shock-loading conditions must be avoided.

The work piece is heated to 500-550 °C in a nitrogen-rich environment, either ammonia or a powder bath. The part is allowed to cool slowly to avoid the formation of undesirable stresses.

Tuftriding

This method is similar to nitriding except that nitrogen and carbon are introduced into the surface of the work piece.This is achieved by heating the part in a molten salt hath for 2—4 hours. The result is a very hard but thinner layer, which is more resistant to shock loading conditions. Its chief advantages are:

A very hard but less brittle surfactr
Resistance to shock loading conditions
Short process times Cost-effectiveness

The work piece is heated to 500—550 °C in a nitrogen- and carbon-rich powder bath. The part is allowed to cool slowly to avoid the formation of undesirable: stresses.