International Journal of Applied Engineering Research ISSN 0973-4562 Volume 13, Number 14 (2018) pp. 11653-11664 © Research India Publications. http://www.ripublication.com 11653 Coatings of Cutting Tools and Their Contribution to Improve Mechanical Properties: A Brief Review Noor Atiqah Badaluddin 1 , Wan Fathul Hakim W Zamri 1* , Muhammad Faiz Md Din 2 , Intan Fadhlina Mohamed 1 and Jaharah A Ghani 1 1 Centre for Materials Engineering and Smart Manufacturing (MERCU), Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia. 2 Faculty of Engineering, Universiti Pertahanan Nasional Malaysia, Kem Sungai Besi, 57000 Kuala Lumpur, Wilayah Persekutuan Kuala Lumpur, Malaysia. (Corresponding Author * ) Abstract Cutting is an important process in the manufacturing industry. It is necessary to use good quality cutting tools in order to maintain the quality of a product. The coating on a cutting tool has a great impact in terms of the mechanical and tribological properties as well as the end results of the product. A cutting tool can made of various types of materials, but the most commonly used material in the industry today is cemented tungsten carbide as its characteristics meet the requirements of manufacturers. To improve the performance of cutting tools, various coatings have been applied to the tools, among them being single coatings, multi-layered coatings, nanocomposites and superlattices. Hierarchical- structured coatings are the latest discovery in the manufacturing industry. This review discusses cutting tools, their functions and coatings as well as their hierarchical structure in order to assist researchers in understanding the appropriate coating structure for cutting tool applications. Keywords: Cutting Tools, Hierarchical Coating, Nano indentation INTRODUCTION The cutting process involves the removal of material from a workpiece to produce a specific design. The quality of the cutting process is assessed in terms of the end result of the product and the lifetime of the cutting tool itself. Cutting tools are made of various types of materials including cemented tungsten carbide, high-speed steel, diamond and boron nitride. All these materials have their own mechanical and tribological properties, but cemented tungsten carbide is the most commonly used material in the industry, especially for steel cutting applications. This is because cemented tungsten carbide is reasonably priced and has a high level of hardness and boiling point. However, the performance of a cutting tool does not depend on the material alone. The performance of a cutting tool can be improved by applying a coating to the surface of the cutting tool. Various types of coating structures and materials can be combined to produce high-performance cutting tools. The coating not only functions to extend the lifetime of the cutting tool but it also acts as a protection against wear, especially against abrasions and adhesions, in cutting tool applications. The strength of the coating is dependent on the material used for the coating, but studies have shown that a more layered structure will further enhance the hardness of the coating and increase its resistance to wear. Currently, a combination of various materials such as TiALN/TiN, TiCN/TiSiN/TiAlN and many more are being used for multi-layered coatings. These multi-layered combinations will produce distinctive mechanical and tribological properties. A recent study on the structure of coatings was carried out by [1], through the introduction of a multi-layered hierarchical coating. This coating consists of 2 or more coating materials arranged according to a hierarchical structure, with different individual thicknesses. According to this study, such a structure can increase the wear resistance of a coating and protect the material from crack propagation. CUTTING TOOLS IN INDUSTRIES The cutting process is a core process that involves various other processes in the manufacturing industry [2]. The cutting process can be defined as a mechanical manufacturing process where a part is formed by removing or separating out a material that is known as the chips until the desired shape is obtained [2]. The unnecessary part will be removed by shear deformation. What is important about the material or tool in the cutting process is that the type of work material should always be harder than the material that is to be processed [2]. This basic fact is very important because it will determine the quality of the final product. Table 1 shows the cutting categories that are being used in today’s industry. These processes are familiar to product manufacturers in the industry.