Technical Report A study of mechanical properties of friction welded mild steel to stainless steel joints D. Ananthapadmanaban a, * , V. Seshagiri Rao a , Nikhil Abraham a , K. Prasad Rao b a St. Joseph’s College of Engineering, Department of Mechanical Engineering, Chennai 600 119, India b I.I.T. Madras, Department of Materials and Metallurgical Engineering, Chennai 600 036, India article info Article history: Received 15 June 2008 Accepted 24 October 2008 Available online 7 November 2008 abstract The aim of this work is to study mechanical property variation under different friction welding conditions for mild steel stainless steel joints. Yield strength, ultimate tensile strength, percentage elongation of the welded joints and hardness variations across the weld interface have been reported. The integrity of the joints have been investigated using optical microcopy and scanning electron microscopy. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Friction welding is a method of manufacturing which is being used extensively in recent times due to its advantages such as low heat input, production time, ease of manufacture and environ- ment friendliness. Friction welding can be used join different types of ferrous metals and non-ferrous metals that cannot be welded by existing fusion welding methods. It is a solid phase welding pro- cess that joins two materials by the friction heat generated by the relative motion of the contact surfaces under the action of an upset pressure. Some of the disadvantages of liquid phase manu- facturing methods like high heat input and usage of non-matching filler wire can be avoided by using friction welding Friction weld- ing parameters such as friction pressure, upset pressure and burn- off length have to be selected based on the parent metals to be welded and prior experience. In this study, friction welding of mild steel to stainless steel has been reported. This combination could be useful in applications like armour plates for tanks where a hard, tough exterior is backed by a softer inner core material. Both theoretical and experimental studies on effect of friction welding parameters on properties of steel have been reported in the literature. Dobrovidov et al. [1] investigated selection of opti- mum conditions for the friction welding of high speed steel R6M5 to carbon steel 45. Mumim Sahin [2] has investigated the hardness variations and microstructure at the interfaces of steel welded joints. While using austenitic stainless steel, negative metallurgical changes like Delta ferrite formation and chromium carbide precip- itation between grain boundaries take place during fusion welding. These changes can be eliminated by friction welding. The effect of friction time on the fully plastically deformed region in the vicinity of the weld has been investigated by Sathiya et al. [3]. The effect of friction pressure on the properties of hot rolled iron based superal- loy has been investigated by Hakan Ates et al. [4]. 2. Materials and methods The materials used in the experiments were cylindrical rods of length 75 mm and diameters 15 mm. The chemical composition of the mild steel and stainless steel are shown in Table 1. The cylindrical specimens were turned to 12 mm diameter in a lathe. They were also faced to prepare the weld surfaces. Further, sough grinding was done with emery paper and the surfaces to be welded were cleaned with acetone just prior to welding. The friction welding machine FWG 20/300-S used is a machine capable of operating with high precision and excellent repeatabil- ity of weld parameters. The spindle is driven by an AC motor. Fric- tion and upset forces are read by a load cell and precisely controlled by a computer. All relevant data of every weld is re- corded. The machine has a stroke of 300 mm and a maximum up- set force of 200 kN can be applied. The spindle motor is of 20 HP, 3 Phase AC and operating speed can be varied from 1 to 2500 RPM. The speed of rotation was kept constant at 1500 RPM. Eight dif- ferent combinations were welded. The friction welding parameters for the eight combinations are shown in Table 2 give below. The quality and integrity of the welds were examined by carry- ing out tensile tests and hardness tests. Optical microscopy of the joints was done to observe changes in microstructure in the inter- faces region. The fractured surface was also observed using scan- ning electron microscopy. 3. Results and discussion 3.1. Macro examination Visual examination of the welded specimens showed uniform and good welded joints. The flash obtained was also symmetric 0261-3069/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.matdes.2008.10.030 * Corresponding author. Tel.: +91 44 24500594; fax: +91 44 24500861. E-mail address: ananth_1out@yahoo.com (D. Ananthapadmanaban). Materials and Design 30 (2009) 2642–2646 Contents lists available at ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes