Experimental and numerical investigation on the friction welding process

Abstract

The friction welding of dissimilar material combinations such as Al 6061 - SS 304, Al 5052 SS 304, Pure Al SS 304, Al 6061 copper, pure Al copper are very important. As some of these weld combinations are used in very critical applications such as aerospace, nuclear power plants, cryogenics, rocket fuel systems, electrical and automotive applications. Therefore the weld strength and its interface properties are extremely important. The failure of these parts can lead to huge losses. The friction welding of these dissimilar materials is more complicated compared to similar materials due to differences in physical, mechanical, chemical and thermal properties. The problems associated with friction welding of aluminum and its alloys to SS 304 and copper are lower weld strength in the inner region, susceptibility to formation of intermetallic compounds, formation of unbond zone at the inner region (central portion), presence of oxides layers at the weld interfaces, non uniform heat generation across the weld interface, unsymmetrical deformation with respect to the plane of the joint interface and large amount of material consumption during welding process. In friction welding with regular joint geometry (flat face to flat face), the heat generated in inner region is lower than outer region. This is because of lower rotation speed of inner region (central portion) when compared to outer region. The heat generation decreases radially as distance from centre to outer periphery of the work piece decreases. Therefore welding starts from the outer periphery and it progresses to inner region, which increases the severity of previously mentioned problems.