International Journal of Research and Scientific Innovation (IJRSI) |Volume III, Issue IX, September 2016|ISSN 2321–2705 www.rsisinternational.org Page 58 Friction Stir Processing (FSP) of Copper and Enhancement of Its Mechanical Properties Using Graphite Powder (C) Md. Noorul Hoda a , Dr. Ranganath M.Singari b , V. Jeganathan Arulmoni b a M.Tech, Department of Mechanical Engineering DTU, Delhi-110042, India b Associate Professor, Department of Mechanical Engineering DTU Delhi-110042, India Abstract: This project investigates change in micro structure; hardness and wear resistance of friction stir processed copper in multiple passes with the help graphite powder. The behavior of copper with graphite powder has been studied with single pass, double pass, triple passé and four passes. A 6 mm triangular pin and 19.95 mm diameter shoulder tool has been used for processing. The optical microscopy (OM) results are also presented for each case. The objective of this project is to investigate change in micro structure, hardness and wear resistance of friction stir processed copper in multiple passes with the help graphite powder. Friction stir processing has the advantage of reducing distortion and defects in the materials. The hardness test, wear test and microstructure test has been successfully examined and results are analyzed. Keywords - Multipass; Friction stir processing; copper and graphite; mechanical properties, Testing. I. INTRODUCTION n today‟s Engineering era, there is high demand and necessity of high strength materials in manufacturing. So, Friction stir processing was developed for micro structural change of metallic materials.[1] Processing/welding parameters, tool geometry and joint design apply significant effect on the material flow pattern and temperature distribution, thereby influencing the micro structural advancement of the material.[2] In FSP, a rotating tool is inserted into an objects and high plastic deformation is produced. FSP is used to improve ductility, induce super plasticity and improve corrosion resistance properties of the material. FSP has been effectively applied to various cast aluminum, magnesium and copper alloys to reduce casting defects and thereby improve mechanical properties of the material. Mixing of metal between the tool shoulder and the plate plays a significant role in influencing the mechanical properties during friction stir process.[3] Modes of metal transfer are visible in the microstructure characteristics, in macrostructure of most processed samples. Tool geometry is the most important aspects of process development. The tool geometry plays a vital role in material flow. FSP tool consist of a shoulder and a pin. The tool has two primarily purpose: localized heating and material flow.[4] In the early stage of tool plunge, the heating results mainly from the friction between pin and work piece. Some further heating results from deformation of the composite material. The tool is plunged into the work piece till the shoulder touches the surface of processing work material. The friction between the shoulder and work material results in the major component of heating. From the heating aspects, the comparative size of pin and shoulder is very important, and the other design characteristics are not critical.[5-7] The shoulder of the tool also provides confinement for the heated volume of material. The 2nd purpose of the tool is to „stir‟ and „move‟ the work material. The uniformity of micro structure and properties is governed by the tool design.[8] Usually a concave shoulder and threaded cylindrical pins are used. Tool rotational speed depends upon the hardness of the work piece.[9] Further if the rotational speed of the tool is very low and traverse speed is low the grain size can be larger in the material which might affect the microstructure, hardness, tensile strength and wear resistance of the composite material. Hence one should go for best possible tool rotational speed and traverse speed in processing. Processing speed is nothing but traverse speed. An increase in traverse speed and decrease in rotational speed may cause reduction in the grain size of the material in stir zone. Generally traverse speed has been used as the processing variable on microstructure and micro hardness. Higher traverse speed influence micro hardness. Axial load is the force acting upon the Friction stir processing tool. It helps the tool pin to plunge into the material and the pressure generated upon the work material by shoulder of the tool. Groove thickness and depth depends upon the amount of powder to be used to make metal matrix II. EXPERIMENTAL SETUP AND PROCEDURE Friction stir processing (FSP) machine from the central workshop of DTU Delhi has been utilized for conducting the process. This machine can be used for the work piece dimension of 200*80*5 mm. For the formation of the work piece, copper is used as a material. So, the sample is cut from the given plate manually using hacksaw. After that, the sharp corner of the samples is rounded by filing for safety purpose. I