Carbonitriding is an austenitic casehardening process (above A3), with the addition of nitrogen (via NH3 gas), used to increase wear resistance and surface hardness through the formation of a hardened surface layer.
Carbonitriding is mainly used to obtain a hard, wear-resistant layer. The spread of carbon and nitrogen increases the hardenability of carbon and low-alloy steels. The carbonitriding process is particularly suitable for the treatment of small components. Deformation is reduced due to the lower temperature used for the above treatment compared to the case-hardening process. Carbonitriding improves the wear and fatigue resistance of carbon and low-alloy steels.
Carbonitriding can be used to treat a wide variety of steels, from low-alloy carbon steels with up to 0.25% carbon to steels with high machinability and sintered components.


Carburizing is a process that releases carbon into a solid ferrous alloy. This is achieved by heating the metal in a carbon-rich atmosphere for a predetermined time.
After carburizing, the parts are hardened and stretched in order to obtain a hardness from the surface layer to the core.
This is a surface hardening process used for low-carbon steels.
Carburizing and hardening produce hard, wear-resistant surfaces, and combining them with a relatively hard but tough core is an excellent combination to withstand wear and mechanical stress.
The depths of the carburized layers can vary from a few hundredths of a millimetre to several millimetres.
Carburizing is frequently used in the automotive, mechanical, hydraulic and textile machinery sectors.


This is a heat treatment process for ferrous metals with medium-high carbon content used to obtain a metallurgical structure called bainitic, which provides greater resistance and less deformation.


This low-temperature heat treatment is generally used after a hardening process to obtain the right hardness-to-tenacity ratio.


This surface hardening process increases wear resistance, surface hardness and fatigue hardness by means of a hardened surface layer while keeping the microstructure of the core unchanged.


Aging is a heat treatment used to increase surface strength and hardness by producing precipitates of the alloy material in the metal structure. Solubilisation is achieved by heating an alloy to a predetermined temperature, for time enough to transform one or more constituents into a solid solution and then cooling it quickly enough to keep those constituents in the solution.

Solubilisation and ageing: Nickel alloys

The properties of nickel-based alloys that can be heat treated can be improved by appropriate heat treatment parameters.


Precipitation heat treatments are used to make materials more resistant by controlled release of constituents to form precipitate aggregates that increase component resistance.


Gaseous nitriding is a thermochemical diffusion process used to increase surface hardness, wear resistance, fatigue, abrasion, friction and seizing resistance through nitrogen diffusion.
Fatigue resistance is mainly increased by the development of surface compressive stresses. The variety of temperatures and depths of the layer allow the adjustment of the different properties of the treated parts.
Nitriding can be applied in various fields such as: valve parts, tappet rollers, springs, extrusion screws, injectors, engine valves, gears, crankshafts, camshafts, moulding dies, aluminium extrusion dies, and plastic moulding dies.
The nitriding process becomes more efficient when steel containing elements that form nitrides of chromium, molybdenum, vanadium and aluminium are used. The process is also used for tool steels, steel for hot machining operations, steel for cold machining operations.
Low-temperature nitriding is used on spring steels in order to extend the fatigue resistance of springs for use in the automotive industry. In principle, all ferrous steels can be subjected to gaseous nitriding.

Post-oxidised nitriding – NITREG® – ONC (NITOX)

NITREG® – ONC (NITOX) treatment is the modern combination of NITREG® controlled potential gaseous nitriding and a subsequent oxidation step followed by an impregnation process using a corrosion inhibiting liquid.
The process gives the surface a uniform dark black colouring which not only increases resistance to corrosion but also improves appearance.
The increase in air pollution, which is now present in all industrialised countries, as well as the widespread use of procedures that develop corrosive agents determine greater risks of corrosion than in the past on metal surfaces of various mechanical parts.
In the same way, the continuous increase in limit stresses on mechanical parts, has resulted in the need for surfaces able to maintain over time optimal characteristics obtained after machining.


This is a nitrocarburizing process which involves the simultaneous diffusion of carbon and nitrogen in the surface of the steel. The purpose of this treatment is to create a hardened surface layer, which improves wear and corrosion resistance, or improved fatigue resistance of the treated steel or cast iron parts, without shape distortions or dimensional changes. In order to maintain a correct concentration of rising nitrogen and carbon on the surface of the metal, Nitreg®-C technology uses the concept of controlling nitride and carburizing potentials (KN and KC).
This is an environmentally friendly alternative but equivalent to nitrocarburizing with a salt bath.
The advantage of KN & KC controlled technology is highlighted when greater resistance to wear and/or corrosion is required. These properties of the particular nitrided iron are not only influenced by the thickness and phase composition of the WL, but also strongly dependent on the relative level of porosity developed in the WL.
KN control is essential to produce the desired WL configuration.

NITREG®-C Accelerates the formation of the compound (white) layer on low-alloy steel; increases and stabilizes the phase content ε in most types of steels, and is a green technology inasmuch as it produces unpolluted waste.

Post-nitriding oxidation / nitrocarburizing

When atmospheric corrosion resistance and an attractive black finish are the predominant requirements, ONC® is the appropriate process.
Its objective is to transform the top of the WL obtained with Nitreg® or Nitreg®-C technologies into a complex spinel-type structure consisting mainly of Fe3O4 type iron oxides.
This post-nitriding oxidation treatment has a clear effect of improving the corrosion resistance of an already nitrided component. This integrated process (e.g. Nitreg® + ONC® or Nitreg®-C + ONC®) simultaneously increases the corrosion and wear resistance of the steel, while giving the surface an attractive dark or black appearance, which is expressly desired by many customers.
ONC®, applied in combination with the Nitreg® Potentially Controlled Nitriding Process or the Nitreg®-C Potentially Controlled Nitriding Process, is a clean technology which in many cases can replace salt-bath chromium plating and nitriding with all their pollution and cost problems.
Depending on the type of steel, parts treated with the Nitreg®-ONC process can easily pass over 200 hours of ASTM B117 salt spray testing before the first corrosion spot appears.

ONC® improves corrosion resistance and intrinsic wear resistance.