Steel nitriding, or diffusion saturation of metal with nitrogen, is a technology in which parts are held in nitrogen-containing gases or dissociated ammonia at temperatures above 500 degrees Celsius. Before nitriding, parts are usually subjected to hardening and tempering (quenching followed by high-temperature tempering) so that the core has a sorbite structure, while nitriding forms a hard nitrided layer on the surface.
Goals and Benefits of Nitriding
The main goals of nitriding are:
- Imparting hardness and strength.
- Increasing wear resistance.
- Improving the anti-corrosion properties of the metal.
Steel nitriding significantly improves the performance characteristics of metal. The process of saturating iron with nitrogen changes its microstructure, which makes it possible to achieve high static and dynamic strength, hardness, wear resistance and corrosion resistance.
Applications of Nitriding
Various metal parts are most often subjected to nitriding, such as:
- Shafts and studs.
- Rods and flanges.
- Gears and rings.
These parts can be up to 900 mm in diameter and up to 1500 mm long, so they must be processed on special equipment. Our company can nitride parts weighing up to 100 kg at a time. Nitriding is carried out in electric furnaces with a steel retort inside, into which heated ammonia is supplied.
Comparison of Nitriding and Carburizing
Steel nitriding can help achieve higher strength than carburizing. After nitriding, parts can be heated to 550–600 °C without loss of hardness, whereas after carburizing, only up to 225 °C.
Nitriding provides more stable steel hardness values. The surface layer of a nitrided product retains its hardness even when heated to 550-600°, whereas after carburizing, the hardness of the surface layer may begin to decrease once the product is heated above 225°. The strength characteristics of the steel surface layer after nitriding are 1.5-2 times higher than after hardening or carburizing.
The Nitriding Process
Since the treatment temperature does not exceed 600°C, structural transformations similar to those that occur as a result of austenitizing during hardening do not take place. This allows cooling at any rate without the risk of martensite formation. For this reason, unlike hardening, the deformation and warping of nitrided parts and tools are insignificant, which simplifies subsequent processing or even makes it unnecessary. That is, finished parts that have already been machined and ground can be nitrided without a finishing allowance, as is required for carburizing.
Nitriding is carried out in special electric furnaces with a sealed steel retort inside, into which the parts are placed. Ammonia (NH3) is then supplied, which dissociates into atomic nitrogen and hydrogen under the effect of temperature. The nitrogen atoms that have penetrated the surface layer of the material then diffuse both along the grain boundaries and through the grains.
Karbaz Equipment and Technical Capabilities
Dimensions of processed parts:
- Rings, gears, flanges, etc. up to 900 mm in diameter.
- Shafts, rods, studs, etc. up to 1500 mm long.
Weight of processed parts: up to 100 kg.
Our company offers high-quality steel nitriding at affordable prices for enterprises of all forms of ownership. We use advanced equipment and technologies to ensure the best processing results. Submit a request on our website, and our manager will contact you shortly.
In conclusion, steel nitriding is an effective technology for improving the performance characteristics of metal parts. Thanks to increased hardness, strength, wear resistance and anti-corrosion properties, nitrided parts last longer and cope better with loads, which makes this process indispensable for various industries.
If you need strengthening technologies and would like to order steel nitriding in Ukraine, our company Karbaz will offer you this service at a favourable price.