The main goal of surface
engineering is to improve the surface mechanical properties of materials while
still maintaining bulk properties - such as mechanical strength, impact
resistance, density, etc. Material surface aspects that engineers consider in
design processes are mostly classified as wear, fatigue, and corrosion.
Although wear and fatigue are considered mechanical damage, they are often
associated with corrosion.
If these types of damage are combined,
the results can be difficult. For example, fatigue fracture of steel parts is
prevented if the applied cyclic stress is less than a specific value known as
the "fatigue limit". However, in the presence of a corrosive
environment, the fatigue limit of materials is significantly reduced, making it
more difficult to determine the fatigue limit. Therefore, the corrosion
resistance of materials is very often increased, while also improving the
resistance to wear or fatigue.
Methods of increasing strength
The methods used in surface
design to control wear and fatigue fractures are divided into two types:
Coating
This includes applying high
performance coatings to the surface of the material. In some cases, very hard
coatings, such as chromium, titanium carbides or titanium nitrides, are applied
to the surface. These coatings generally have good corrosion resistance and
high abrasion resistance. However, unavoidable coating defects such as
holidays, cracks and holes can cause corrosion problems, exposing the substrate
to a corrosive environment. There are many different methods for applying
abrasion and fatigue coatings, such as electroplating, physical vapor
deposition (PVD), chemical vapor deposition (CVD), pulsed laser (PLD) coating,
and so on.
Surface modification
This method changes both the
surface structure and the chemistry of the material without applying an
external coating; the metal surface has been modified to meet the surface
requirements. Surface modification is usually performed by dispersing one or
more elements on a metal surface. These types of processes are often referred
to as diffusion coatings.
Nitriding Process
Nitriding Solutions is one of the most important and common surface
modification processes can improve the corrosion resistance of steel parts by
increasing the resistance to wear and fatigue. In this process, atomic nitrogen
penetrates the surface of steel and reacts with substrate atoms (mainly iron)
to form nitrides. Metallic nitrides are hard and increase the wear resistance
of the surface. This is a well-known heat treatment process for steel parts to
improve their wear and fatigue resistance. To know more about advanced nitriding process,
visit the website http://www.ans-ion.net/.
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