Gas nitriding is a thermochemical surface heat treatment used to harden the outer layers of steel components through nitrogen diffusion and the formation of nitrides.
The process increases surface hardness, wear and galling resistance, fatigue strength, reduces friction, and ensures high dimensional stability.
The treatment is applied to nitriding steels, tool steels, carbon steels, quenched and tempered steels, and cast irons.
CHARACTERISTICS
Type of treatment:
Thermochemical surface heat treatment
Surface appearance:
Uniform and compact surface with a characteristic grey coloration.
Case depth:
Effective case depth is defined according to hardness penetration classes (NtE – UNI 5478:1999), typically ranging from 0.1 to 1 mm.
Process description:
the component is heated to temperatures between 500 and 550°C and held in an ammonia atmosphere.
During ammonia dissociation, nascent nitrogen is released and diffuses into the steel surface, reacting with alloying elements to form nitrides.
The nitrided layer consists of a hard outer compound layer (“white layer”) and an underlying diffusion zone.
ADVANTAGES
- Limited dimensional distortion
- High resistance to abrasive and adhesive wear
- Increased fatigue resistance
PROCESSABLE MATERIALS
- quenched and tempered steels (C45, 42CrMo4)
- special grades (31CrMo12, 34CrAlNi7, 39CrAlMo6)