Surface engineering envisages tailoring of the surface characteristics of a component or structure to suit various requirements for different applications in a variety of environment. Modification of surface characteristics without changing the properties of the bulk material has opened up many new diversified applications in addition to permitting use of easily available and less expensive materials. Instead of using in entirety, it is possible just to use a thin overlay of the material on a suitable substrate and thus make effective use of rare and expensive materials. Many coating deposition techniques and surface treatments are available for the modification of surface characterization. If the material is added to the surface, the process is referred to as coating deposition process; however, if the surface microstructure and / or chemistry is altered, then the process is referred to as a surface treatment process. Selection of the coating deposition techniques depends on the functional requirements, shape, size and properties of the substrate, coating material, compatibility, adhesion, coating equipment and cost. Surface coating technology has received considerable attention in recent years. It improves corrosion, friction, wear, fatigue and oxidation resistance and other properties of components. Industries all over the world suffer a considerable financial losses because of the wastages caused by mechanical wear and corrosion. Much of these losses could be turned into savings by using the existing and developing knowledge of surface coating technology. Vapour deposition techniques are normally used for deposition of thin coatings (<10 mm). Ion plating and sputtering are the complex processes requiring vacuum deposition chambers but these processes normally do not require any post treatment. Coatings enable to use the component in highly aggressive environments. This requires suitable technique for modification or deposition to achieve the desired properties of the coating. Ceramic coatings have tremendous potential for applications in many fields for their superior mechanical and wear resistance. Nano-crystalline coatings, multi-layers and compositionally modulated coatings are an advanced field of surface modification because of their superior mechanical, tribological and corrosion resistant properties. By suitably controlling various deposition parameters, coatings having desired properties can be tailor-made.
Characterization with respect to composition, thickness, adhesion, phase analysis, microstructure, surface topography and performance analysis with respect to wear and corrosion of the coatings are important aspects. Quality control with respect to chemical composition, mechanical properties and resistance in aggressive environment is necessary to meet the stringent requirement of coating-substrate combination. Physical vapour deposition (PVD) processes are increasingly being used for the deposition of variety of coatings on tools and components to improve wear and corrosion resistance. Titanium nitride (TiN) coating has been accepted as a universal hard coating for tools in industrial practice and for decorative applications. It is recognized that new coatings such as Ti(CN) and (Ti-Al)N are not so much an alternative but rather an addition to TiN coatings. In addition to these, chromium nitride (CrN) coating has also envisaged interest. Desired properties of such coatings mainly depend on their microstructure and composition which can be controlled by varying the partial pressure or flow rate of reactive gas, substrate temperature and surface ion bombardment during deposition. Coatings applied by vapour deposition techniques are basically decorative and functional types. Decorative coatings are widely used in the automotive, home appliances, hardware, costume, jewelry etc. Functional coatings have numerous application such as reflection, anti-reflection, filter, beam splitter coatings on optical instruments; conductive, dielectric and semi conductor coatings on electronic components; hot corrosion resistant, coatings on air craft and missile parts; oxidation resistant coatings for gas turbine blades and compound coatings for cutting, drilling and forming tools, moulding dies, machine parts etc.