What Does Ion Nitriding Mean?
Ion nitriding is a surface-hardening technique that uses DC glow discharge to introduce elemental nitrogen to the surface of a metal part for subsequent diffusion into the material. The thermo-chemical process involves bombarding the material surface (held at elevated temperature) with energetic nitrogen ions. This allows the nitrogen ions to diffuse and form a case-hardened surface with improved surface properties.
Ion nitriding is also known as plasma nitriding.
Corrosionpedia Explains Ion Nitriding
A basic ion nitriding machine has a vacuum pump that is used to evacuate the interior of the machine. DC voltage is applied to the workpiece, which acts as the cathode while the inside wall of the machine is the anode. Once the voltage is applied to the electrodes under reduced atmospheric pressure, the glow discharge occurs across them. Electrons are released from the cathode and move toward the anode. These electrons collide with gas molecules which are introduced to the machine in the form of a mixture of nitrogen, hydrogen and an optional carbon spending gas. The gas molecules are converted into ions which are accelerated towards the workpiece (cathode) where they collide with the surface and penetrate into the material.
The ion nitriding process can be adjusted to form customized layers and hardness profiles. The desired depth of penetration and material hardness can be achieved by controlling the temperature, concentration of the gas mixtures, voltage and current.
The ion nitriding of metal is mainly used on steel, but also applicable to titanium, aluminum and molybdenum. The benefits include improved:
- Surface properties
- Wear resistance
- Fatigue strength
- Friction properties
- Corrosion resistance
- Load-bearing capacity of dynamically loaded components.
- Energy efficiency
Ion nitriding is widely used on high-reliability components in:
- Medical applications
- Motor vehicles
- Other machinery
Typical components include:
- Camshafts, cam followers, crankshafts, long shafts
- Pressure-die-casting tools and cold forming tools
- Extruder screws
- Extrusion dies, forging dies and die-casting tools
- Injectors and plastic-mold tools
- Gears, valve parts, clutch and engine parts