Surface Engineering by Friction Stir Processing and Friction Surfacing

Introduction: The Importance Of Surface Engineering

In day today life, whenever we are purchasing any article, the first thing we notice in our selected object is the surface appearance. Even if there is a small scratch on its surface, we reject the article and ask for a new article of the same brand and colour. The price of any article is dropped down if there are any damages externally. Hence, the surface appearance is very important immaterial of whether it affects the functionality or not. However, in engineering component, though aesthetic appeal is given importance, functional performance is primary. The surface is the part which experiences the most material degradation in engineering applications. Hence in most of the applications, surface modification is required to delay the material degradation and to enhance the functional performance of the component. The factors responsible for material degradation can be physical, mechanical, biological or a combination of these. Applying any protective measure to an engineering component involves the following four steps:

• 1.

  Cleaning the surface or surface preparation

• 2.

  Selection of suitable surface modification technique by analysing the reason for material degradation,

• 3.

  Process control to obtain the desired properties and

• 4.

  Maintenance of the modified surface.

Surface engineering embraces those processes which modify the surfaces of engineering components to improve their in-service performance, useful working lifetimes, aesthetic appearance or economics of production.

The purpose of surface modification may be to minimize corrosion, reduce frictional energy losses, reduce wear, to provide thermal insulation, to exclude certain wavelengths of radiation, to promote electronic interactions, electrically insulate or simply improve the aesthetic appearance of the surface.

Any surface engineering technique involves two steps viz:

• 1.

  Surface Preparation, and

• 2.

  Surface Treatment.

Surface Treatment

After cleaning the surface, the selected surface treatment technique should be applied. Surface treatments can be divided into three broad categories viz:

• 1.

  Treatments modifying the surface without altering the substrate‘s chemical constitution,

• 2.

  Treatment changing the surface layers by altering the alloy chemistry,

• 3.

  Treatment involving addition of layers of material to the surface.

Various surface treatment techniques based on different categories is shown in Table 1.