Gas Nitriding
The Defenition:Gas nitriding is a case-hardening process whereby nitrogen is introduced into the surface of a solid ferrous alloy by holding the metal at a suitable temperature in contact with a nitrogenous gas, usually ammonia.
The nitriding temperature for all steels is between 495 and 565°C (925 and 1050°F).
Some Nitridable Steels
Of the alloying elements commonly used in commercial steels, aluminum, chromium, vanadium, tungsten, and molybdenum are beneficial in nitriding because they form nitrides that are stable at nitriding temperatures.
Molybdenum, in addition to its contribution as a nitride former, also reduces the risk of embrittlement at nitriding temperatures.
Other alloying elements, such as nickel, copper, silicon, and manganese, have little, if any, effect on minding characteristics.
Although at suitable temperatures all steels are capable of forming iron nitrides in the presence of nascent nitrogen, the nitriding results are more favorable in those steels that contain one or more of the major nitride-forming alloying elements.
Because aluminum is the strongest nitride former of the common alloying elements, aluminum-containing steels (0.85 to 1.50% Al) yield the best nitriding results in terms of total alloy content.
Chromium-containing steels can approximate these results if their chromium content is high enough. Unalloyed carbon steels are not well suited to gas nitriding because they form an extremely brittle case that spalls readily, and the hardness increase in the diffusion zone is small.
Principal reasons for nitriding are:
To obtain high surface hardness
To increase wear resistance and antigalling properties
To improve fatigue life
To improve corrosion resistance
To obtain a surface that is resistant to the softening effect of heat at temperatures up to the nitriding temperature.
BEBON STEEL can provide Nitridable Steels immediately, if you need Nitridable Steels, please be free to contact us.
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