The Applications of Metal Matrix Composites (mmcs)

The applications of metal matrix composites (MMCs) are being increasing day by day in a number of industries, especially in aerospace and automobile industries. These innovative materials open up unlimited possibilities for modern material science and development; the characteristics of MMCs can be designed into the material, custom-made, dependent on the application. From this potential, metal matrix composites fulfill all the desired conceptions of the designer. Metal matrix composites are formed by a combination of metal matrix and hard reinforcing phase. Incorporation of silicon carbide particles attributes towards their superior specific strength, specific stiffness, high-temperature capability, lower coefficient of thermal expansion and better wear-resistance. (Houyem Abderrazak and Emna Selmane Bel Hadj Hmida 1996). For many researchers, the term metal matrix composites (MMCs) is often equated with the term light metal matrix composites (LMCs) because of their high strength to weight ratio (low density high tensile strength). Substantial progress in the development of light metal matrix composites has been achieved in recent decades so that they could be introduced into the most important applications. In engineering, especially in the automotive industry, LMCs have been used commercially in fiber reinforced pistons and aluminum crankcases with strengthened cylinder surfaces as well as particle-strengthened brake disks [1]. As they are harder comparatively they are generally difficult to machine.

Previous literature indicates that polycrystalline diamond tools (PCD) is mainly used for the machining of particulate reinforced MMCs because it shows less tool wear and a useful tool life when machining these materials with PCD tools, which is harder than alumina Al2O3, and silicon carbide (SiC) and it also does not have a chemical tendency to react with the workpiece material. However, due to the extremely high cost of PCD tools, many industries limits their use and shows interest in less expensive tools like cemented carbides and ceramics to machine these materials.

In this paper, an investigation is being carried out for the machinability of the LM13/SiC metal matrix composite at different cutting speeds, feed rates and depth of cuts with the help of tungsten carbide tool. The influence of these parameters on the surface roughness and tool wear is investigated and it is observed that tool tip temperature increases with increase in cutting speed. At high speeds, surface finish is least affected. Surface finish deteriorates at high feed rates; hence to obtain good surface finish, feed rate may be kept low. At low speeds cutting force are high & tendency of work material to form a built-up edge is also stronger. At lower speeds, surface roughness increases with increasing feed but at higher speeds surface roughness is less dependent on feed.