Kaasupolttonitridöinti

Kaasupolttonitridöinti, often shortened to gas nitriding, is a thermochemical surface hardening process used to improve the hardness, wear resistance, and fatigue strength of steel. It involves diffusing nitrogen into the surface of the steel at elevated temperatures, typically between 500 and 580 degrees Celsius. The nitrogen is usually supplied by a gas atmosphere, such as ammonia (NH3), which dissociates at these temperatures to release atomic nitrogen. This atomic nitrogen then diffuses into the steel's crystal lattice.

The process creates a hard, wear-resistant layer known as the compound layer, which is primarily composed of iron nitrides. Beneath the compound layer is a diffusion zone, where nitrogen has diffused deeper into the steel, increasing its hardness and strengthening the core. The depth and characteristics of the nitrided layer can be controlled by adjusting the process temperature, time, and the composition of the gas atmosphere.

Gas nitriding is a low-distortion process, meaning it causes minimal dimensional changes to the workpiece, making it suitable for components that require tight tolerances. It is commonly applied to alloy steels containing nitride-forming elements like chromium, molybdenum, and aluminum, as these elements promote the formation of stable and hard nitrides. Applications include gears, crankshafts, camshafts, dies, and other machine parts subjected to high wear and stress. The process does not typically involve quenching, further contributing to its low distortion.