Wear is a
progressive loss of surface material from its location by contacting surfaces
in relative motion. From this definition, we could develop different wearing
occurring in the metal surface by either corrosion, abrasive, adhesive, erosive
or oxidation. The human life is been effected by wear life of mechanical
components as they destruct the material components in many wearing methods. The range of wearing devices and components in
the human life nowadays in endless, for consideration human teeth, joints,
cams, piston rings, gaskets, tires, cannon barrels, drills, pump impellers, casing,
rocks and roads. The list is wide and long which shows that the wear is a
natural phenomenon that occurs without possibility to stop it forever. There
are ways that could reduce and limit the wearing of mechanical components by
using coating or increasing the mechanical properties of the material used. In
addition, to resist wear the material selected is an appropriate to that
environment that is going to deal with to reduce surface temperature, stress or
There many types
of wearing that influence the surface of the material and change the microstructure
of the material. This will result on destructive damage and capable to destroy
the material eventually if the wear continually affect in the metal.
Classification of wear:
Various forms of wear exist in industry and in our
daily life. Different methods can be used to categorise a wear process. For
examples, wear can be divided as
wear and unlubricated
wear and mild wear;
wear, rolling contact wear
and impact wear.
However, all wear process involve one or a combination of wear mechanisms
including abrasion, adhesion, fatigue and oxidation or
other tribo-chemical actions.
In order to solve a wear problem, it is necessary
to understand the underlying wear mechanism. In the following section, we will
introduce two most frequently encountered wear mechanisms in industry, i.e.
wear by abrasion and wear by adhesion. Oxidation wear will also be addressed
since it is a mild form of wear. If wear can not be avoided at all, changing
its nature from abrasion or adhesion to oxidation (e.g. by surface engineering
the contacting parts) can considerably reduce the wear rate. We shall mainly
discuss wear of metallic materials, although all solid material, e.g. metal,
ceramic, polymer, can suffer from wear damage.