Nitridization

Nitridization is a thermochemical surface treatment process used to harden the surface of metals, particularly steel and titanium alloys. It involves diffusing nitrogen atoms into the surface layer of the material, forming hard nitride compounds. This process significantly increases the surface hardness, wear resistance, and fatigue strength of the treated component.

The nitridization process typically occurs at elevated temperatures, usually between 400 and 600 degrees Celsius, and in a controlled atmosphere containing nitrogen. Various methods can be employed, including gas nitriding, salt bath nitriding, and plasma nitriding. Gas nitriding involves exposing the metal part to ammonia gas, which dissociates at high temperatures to provide the necessary nitrogen. Salt bath nitriding uses a molten salt bath containing nitrogen-rich compounds. Plasma nitriding utilizes a glow discharge to create a plasma rich in nitrogen, which then diffuses into the metal surface.

The depth and properties of the nitrided layer can be controlled by adjusting the temperature, time, and nitrogen potential of the atmosphere. The resulting nitride layer is typically very thin, ranging from a few micrometers to several hundred micrometers, but it provides excellent surface properties without significantly altering the core properties of the material. Nitridization is widely used in industries such as automotive, aerospace, and tooling for components like gears, crankshafts, camshafts, and cutting tools.