IJISET - International Journal of Innovative Science, Engineering & Technology, Vol. 2 Issue 12, December 2015. www.ijiset.com ISSN 2348 – 7968 Comparison of Friction Welding Technologies D. Rakesh Raghavendra 1 , Dr.Sethuram 2 .Dr.V.P.Raghupathy 3 1 student at pes institute of technology, (rakeshragzd@gmail.com) 2 professor at pes institute of technology,(sethuramd@pes.edu) 3 professor at pes institute of technology. PES Institute Of Technology, Bengaluru Abstract Linear friction welding is a solid state joining process in which a joint between two metals can be formed through the contact of a plasticised layer at the interface of the adjoining specimens. This plasticised layer is created through a combination of frictional heating, which occurs as a result of pushing a stationary work piece against one that is moving, in a linear reciprocating manner, and applied force. The process is currently employed as a niche technology for the fabrication of titanium alloy bladed disk (blisk) assemblies in aero- engines,. However, interest is growing in utilising the process in a wider range of applications that also employ non aero-engine metallic materials. Introduction Friction welding is a new method of joining two materials in solid state. This method entails thorough understanding of how coalescence between joining faces occur so that sound components are produced. The basic principles that one needs to be fully aware of are the following: The concept of static and sliding friction and how the frictional forces and consequential heat are generated and The presence of contaminated and oxide layers in a material surface and how it prevents coalescence to occur and Unevenness of the surfaces at microscopic scale and how this can be dealt with so as to prevent asperities and How plastic deformation can be effected so that unwanted contaminated and oxide layers can be ejected out and the Diffusion of atoms at the interface which may result in undesirable formation of inter-metallic compounds. Once the principles as stated above are understood, then engineering aspects such as what are the friction welding parameters that govern effective coalescence have to be arrived at. These require elaborate computations of the parameter ranges that have to be set in the machine. One also should understand the consequences of welding outside the range in each parameter. After going through the science and engineering aspects, it is imperative to have a thorough knowledge of different types of friction welding technologies and where these can be applied. Each type of technology is unique and require an in-depth study of the benefits and limitations of each so that best results can be obtained. The technological intricacies also call for understanding the servo- mechanical systems that are needed to apply the forces, rotational, orbital and linear motion devices that are required to effect dynamic motions, monitoring systems that have to be developed to control all the welding parameters and NDT techniques that have to be employed to assess the soundness of the joints etc. The purpose of this article is to highlight the basics of the above stated points so that holistic pictures of the friction welding technologies are garnered. Concept of static and sliding friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. When surfaces in contact move relative to each other, the friction between the two surfaces converts kinetic energy into thermal energy. Dry friction resists relative lateral motion of two solid surfaces in contact. The two regimes of dry friction 1