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.
Gas
sulphonitriding is the original method of thermo-chemical treatment of steel
and cast-iron parts of machines and mechanisms.
The process
is carried out in retort furnaces, in an atmosphere of ammonia and sulphur vapours,
at a temperature of 500 - 650°C and within a few to several hours, therefore we
have two deep furnaces at your disposal.
We perform
the treatment of elements made of all iron alloys, both steel and cast iron,
using the gas sulphonitriding method. This technology is especially recommended
for machining elements of machines and mechanisms operating in dry or boundary
friction conditions, e.g., worm wheels, pins, camshafts, bearing bushings,
valve guides and valve lifters, cam mechanisms, cylinder liners, and can be
performed on ready-made elements.
Due to the
depassivating (surface activating) effect of the addition of sulphur vapours to
the atmosphere of partially dissociated ammonia, we are able to extend the
scope of use of the gas sulphonitriding process. Thus, we offer a service of
high-chromium steels' nitriding (stainless, heat-resistant and acid-resistant),
on which hard diffusion layers with high resistance to scuffing and wear are
created repeatedly. They are intended for use in internal combustion engines, (e.g.,
exhaust valves) and elements of devices for thermal energy, chemical and food
industry.
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 below 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, shown by an increase in strength properties and a
decrease in plastic properties.
The aging
effect occurs when the temperature is too high. It involves 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.
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.
We carry
out orders from a wide range of services in the field of annealing.