Nitriding
is a process that involves the production of a hardened surface layer by the
precipitation of nitrides.
Special
grades of steel are intended for nitriding, containing the addition of nitrogen-forming
elements: chromium, molybdenum or vanadium, previously subjected to appropriate
heat treatment. However, hardened layers with different properties can be
produced on virtually all steels.
After these
processes, a thin layer of nitrides and precipitation of iron and / or other
elements nitrides appears on the metal surface, not exceeding a total thickness
of 0.6 mm.
This layer
has several very desirable properties. First of all, it is very hard, and its
resistance to corrosion and abrasive wear is much higher than that of ordinary
steel.
We offer
conventional and controlled low-pressure nitriding in pit furnaces.
The basis
for controlling the degree of nitrogen saturation of surface layers with
nitrogen in the process of vacuum nitriding is a compromise between the
increasing nitrogen potential of the atmosphere and the decreasing adsorption
of ammonia molecules on the surface along with the reduction of the pressure of
the working atmosphere.
The complex
of high mechanical properties of vacuum nitrided layers makes this technology
particularly suitable for surface hardening of machine elements operated in
conditions conducive to contact fatigue - in rolling, rolling, sliding or
sliding friction conditions. Thus, as examples of application, one can mention
devices like heat-treated gears, crankshafts, cams, form couplings, spline
surfaces etc.
The vacuum
nitriding process can also be applied to cutting tools, as well as all kinds of
dies and punches. The formation of a hard and non-brittle nitrided layer on
these tools and devices leads to a multiple increase in their durability.
After
hardening, all steels show reduced plastic properties and unfavourable
stresses.
In order to
eliminate them, a heat treatment procedure is carried out, involving heating
the previously hardened material, heating and cooling it in order to obtain the
optimal structure and properties.
We offer
low, medium and high tempering in the temperature range of 180-650°C. It is
possible to carry out the processes in the presence of shielding gas, and in
the case of highly personalized requirements for the highest purity, the
implementation of the vacuum tempering process.
It involves
heating the previously supersaturated alloy to a temperature lower than the
limit of solubility, heating at this temperature and cooling it down. During
the aging process, the excess component in the supersaturated solid solution is
released in the form of highly dispersed phases.
In some
cases, the aging involves intermediate phases and Guinier-Preston zones, in
which they segregate atoms dissolved in the solvent lattice.
Aging
causes strengthening, manifested by an increase in strength properties and a
decrease in plastic properties.
When the
temperature is too high, the aging effect occurs, consisting in coagulation of
the precipitates and the loss of their coherence, which does not increase the
hardness in relation to the supersaturated state, but on the contrary - reduces
it.
Sometimes
aging occurs at room temperature, then it is called spontaneous aging.
Aging can
also be an undesirable process, e.g., in deep drawing sheets and boiler steels,
as it reduces plastic properties and increases brittleness.
A method of
heat treatment of the material, which usually involves heating the steel to a
specific temperature, heating it at this temperature and cooling it in order to
obtain structures close to the equilibrium state.
We
distinguish between recrystallization annealing, homogenization, stress relief,
complete, isothermal and spheroidizing annealing.
In the
field of annealing, we carry out orders from a wide range of services.