Nitreg®: Potential-Controlled Nitriding
objective of nitriding is to increase the hardness of
the component’s surface by enriching it with nitrogen.
Of the three traditional methods Nitrex does not employ
salt bath techniques due to their environmental and
safety risks. Plasma nitriding is described later in
this section and traditional gas nitriding is gradually
being phased out thanks to the development of the Nitreg®
family of processes.
General principles of the various nitriding methods and
an explanation of potential-controlled techniques are
described in more detail in an extension of this page,
accessible by clicking
Nitreg® is a
modern process, capable of meeting the metallurgical
requirements of all nitriding specifications that may
have been originally written for salt bath, plasma or
traditional gas nitriding. The ability to control the
concentration of nitrogen in the surface allows the user
to control the growth of the compound layer virtually
independently from developing a desirable diffusion
zone. This approach facilitates not only meeting any
specification requirements but it also makes it possible
to improve on them by allowing tighter tolerances to be
satisfied, particularly with regard to the thickness and
properties of the compound layer.
Summary of Benefits:
control of the thickness of the compound (white) layer
and its properties
elimination of closed nitride networks within the
control of case depth
control of surface hardness
family of derivative and related processes.
shorter cycle time of the Nitreg® process carried out
predominantly on carbon and low alloy materials.
objective is to reliably produce a nitrided case with
typically increased WL content and a particular nitrided
phase configuration in the WL.
Nitreg®–C is a controlled version of ferritic
nitrocarburizing. It allows for precise Kn control
during the process. The additions of carbon bearing
gases to the nitriding atmosphere help to increase the
relative content of the epsilon phase.
advantage of a Kn controlled technology is best
evidenced when increased wear and/or corrosion
resistance is sought. Such properties of the nitrided
case are not only influenced by the thickness and
relative phase composition of the WL. They also strongly
depend on the relative level of porosity developed in
Kn control is essential in producing the desired WL
Example of various
porosity levels achieved through Kn control are shown
Increased wear/corrosion resistance on selected alloys
Excellent process reliability
ONC®: In-process Post-Nitriding/Nitrocarburizing
resistance to atmospheric corrosion and an attractive
black finish are the predominant requirements, ONC® is
the appropriate process.
objective is to transform the very top portion of the WL
obtained with either Nitreg® or Nitreg®-C technologies
into a complex spinel type structure consisting mostly
of Fe3O4 type of iron oxide.
a post-nitriding oxidation treatment has a net effect of
enhancing the corrosion resistance of an already
nitrided component. This integrated process (i.e.
Nitreg® + ONC® or
Nitreg®-C + ONC®) simultaneously enhances corrosion
and wear resistance of steel, while giving the surface
an attractive dark or black appearance, expressly
desired by many customers.
ONC®, applied in combination with the Nitreg®
potential-controlled nitriding process or the Nitreg®-C
potential-controlled nitrocarburizing process, is a
clean technology that in many instances can replace
chrome plating and salt bath nitriding with their
inherent problems of pollution and cost.
Depending on the type of steel, parts treated in the
Nitreg®-ONC process can easily pass well over 200 hours
of salt-spray test per ASTM B117 before the first
corrosion spot appears.
Fig. 2 shows a comparison of metallurgical and
corrosion test results obtained on three materials
treated by the Nitreg®-ONC process.
Improved corrosion resistance
Attractive black surface finish
Inherent wear resistance
Potential-Controlled Nitriding of Stainless Steel
applying to nitriding of stainless steel or refractory
alloys are no different than those for the other groups
of steels, with one exception.
The exception is
the proprietary de-passivation stage that allows for a
removal of oxides of alloying elements such as Cr, Ni
and others which, if not removed, will effectively block
the nitriding process. The same way they block the rust
formation on the stainless steel surface.
All types of
stainless steel can be nitrided. The martensitic,
austenitic or PH materials inclusive.
Example of a nitrided stainless steel part.
Potential-Controlled Nitriding of Stainless Steel
is a surface hardening process that improves the wear
and galling resistance of stainless steel components
without affecting the inherent corrosion resistance.
Does not alter
chemical composition of alloy
Has no effect on
the steel’s non-magnetic nature
No change in the
color, shape or size
hardened even small bores, tight grooves and sharp
no waste pollution
Hastelloy C22 and
Inconel 625 and
Nitriding of Titanium Alloys
used mostly in the aerospace and defense industries can
also be successfully gas nitrided leading to an
increased wear resistance and providing an attractive
The technology is
not widely known since the applications involved are
also very specific. For best results consult with our
engineers who will advise you on certain unique aspects
of the manufacturing sequence of operations.
Blac-Tride® Post-Nitriding/Nitrocarburizing Oxidation
Blac-Tride® is a proprietary Nitrex Metal post-oxidation treatment performed after the Nitreg® nitriding process and Nitreg®-C nitrocarburizing process for simultaneous improvement of wear properties and corrosion resistance.
The flat black color of Blac-Tride® provides a uniform, aesthetically pleasing appearance while maintaining the mechanical and tribological properties of the nitrided or nitrocarburized component.
Blac-Tride® is available exclusively to clients of our heat treating services and is used for products across a wide range of markets from brake discs, shafts, screws, firearm components to sporting goods.
As an alternative
to gas nitriding, nitriding plasma (ion) nitriding
process has been developed to overcome the shortcomings
of the earlier traditional uncontrolled gas nitriding
processes and to offer certain operational advantages
that gas nitriding does not have.
essentially a gas nitriding treatment in which the
method of delivering nitrogen atoms to the surface of
nitrided components is quite different from the standard
gas nitriding processes. It occurs at a very low
pressure and under high voltage.
metallurgical, tribological and mechanical properties
standpoint the properties of nitrided case obtained with
Nitreg® and well controlled plasma technology are
certain distinct advantages such as:
The ease of
masking the component surface where nitriding is
to be avoided.
nitride low density powder metallurgy parts
Ask us for an
advice about which nitriding method is better suited to
If your drawing
calls for "ion" or "plasma" nitriding we are at your
carburizing is a state-of-the-art thermal process where
carburizing is effected under very low pressures. First
the parts are heated in vacuum to above the
transformation temperature of the alloy. Then they are
exposed to carbon-carrying gas, or gas mixtures, under
partial pressure. Nitrex has developed a revolutionary
process called "Pulse- Pressure", a method quickly
becoming the industry standard.
conventional carburizing, the main advantages of the
results to within ±0.001" (±25µm),
significantly reduced size changes and
control of the surface layer chemistry,
is environmentally friendly.
The basic aspects
or carburizing in general are described in the
Conventional Carburizing section.
It is a
thermal process of simultaneously diffusing both carbon
and nitrogen into ferrous alloys under partial pressure.
This leads to an extremely hard and wear resistant
surface. Vacuum carbonitriding is a significant
improvement over conventional gas carbonitriding. The
process contains all of the inherent benefits of vacuum
carburizing, but also has the additional benefit of
precise computer control of surface ammonia content.
Furthermore, this process does not require any
additional refractory burn-outs so not only is the end
product of higher quality, but it is often less
expensive than with competing conventional gas