Custom «Surface Engineering» Essay Paper

Question 5

There are a number of theories which were proposed to explain adhesion wear phenomenon. Archard is one of the proponents of a theory to explain this phenomenon. In his theory, Archard derived an equation to describe sliding contact wear basing on asperity contact theory. In his theory, Archard assumed that:

• The yield pressure, designated by P in the equation is assumed to deform plastically.
• Also, it is assumed that occurrence of contact is only between a number of projections os diameter designated by d in the equation and the contact are.
• Lastly, the resulting fragments will have a hemispherical shape.

Basing on the above assumptions, Archards adhesive wear equation can be derived as below.

In the derivation process, the following symbols will be used to represent as explained below.

d – Diameter

p – Yield stress of the material during sliding

Q – Volume of weariness

n – Number of point of contact

W – Total applied load

k – Constant of proportionality

Since the diameter is d, then the contact are can be gotten by

Contact area =

This contact area will bear a load as, 

Where P is the yield stress of the material

From the assumption that the resulting fragrance is hemispherical, then the volume of each fragment will be can be calculated by:

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Thus we can determine the volume of weariness, Q as

Q = ==

Where n is the number of points of contact

From this, we can deduce that the projection is carrying a load of                                                                      

Thus the total applied load is given by:

W =

Since it has been proved experimentally that a percentage of contact will result in particle of weariness, then the equation becomes

This is the Archard Equation.

The equation will not give the exact value of weariness because there have been a lot of assumptions in the derivation of the equation.

Question 6

Surface treatment without changing the composition of steel

Electroplating

Electroplating refers to a technique that is mostly used to enhance specific surface properties of certain metals or plastics. This process entails using electrical current to mobilize metal cations from an electrode immersed in a solution to deposit a conducting object. This improves wear and tear properties, and for corrosion protection.

The process of electroplating

• The metal to be used in this process is identified and cleaned to remove oil, dirt and any other debris from the surface.
• Then metal is eventually descaled with appropriate acid discaler.
• After descaling, plating is done which involves electroplating as shown in the diagram below

This technique is used by Premier plating works limited to carry out electroplating on stainless steel. This is done to enhance hardness and scratch resistant. Some of the metals used by this company include silver, zinc, brass among others. The company utilizes specialist pretreatment process to electro-coat still and as a result, there is provision of a very bright surface which is both corrosive and scratch resistant. The products from this company are largely sold in UK which is associated with wear and tear due to corrosion.

HIP (hot isostatic Pressing) Cladding

This is the process of applying one metal to the surface of another. This results in a high a maximum bonded strength that results from subjecting the interface to a pressure of up to 1000 ATM at high temperatures which enhances diffusion. This method is specifically used by Bodycote Plc. to reduce or eliminate internal porosity in metals such as steel. Also the method facilitates densification of metal eventually resulting very superior quality of metals.

Weld Cladding

This process involves depositing molten metal onto metal surface for instance steel through use of welding techniques. It is mainly used in steel to enhance corrosion resistance and wear resistance properties.

Surface treatment that changes the composition of steel surface

Plasma spraying

In this process, the material to be used as a coating is introduced in a plasma jet which is originating from plasma torch. Plasma spraying results into a very superior quality coating as a result of combination of high temperature, relatively less reactive spraying medium such as argon, heat source with high energy level and particles having a high velocity

Bodycote Plc. Being the major company involved in production of steel, it uses plasma spraying to enhance the surface properties of steel