Quality characterization of dissimilar laser welded joints of Ti6Al4V with AISI 304 by using copper deposition technique

Dissimilar metal welding leads to the development of brittleness in the welded joints due to incompatibility in mechanical and physical properties of the metals to be joined. To overcome such brittleness, suppressing the formation of intermetallic compound is the key factor for attaining reliable welded joints. The present study attempts to find the possibility of obtaining joints of crack-free surface in laser butt welding of Ti6Al4V with AISI 304 stainless steel sheets using intermetallic layer through electroplating process. Laser welding on Ti6Al4V titanium alloy with AISI 304 stainless steel sheets of 5 mm thickness has been performed providing copper as an intermetallic layer using electroplating process. Electroplating of the welding edges of two different materials was carried out with and without adding sulphuric acid in the electrolyte solution. The electroplating results indicate that addition of sulphuric acid in the solution increases the thickness of the coating. Presence of copper at the welding edges provides compatibility between Ti6Al4V and AISI 304 during the laser welding process and reduces brittleness. Laser welding was conducted using 3.5-kW CO2 laser with 3-m/min welding speed. The quality of weldment was characterized by macrostructure analysis by scanning electron microscope (SEM), analysis of composition of weldment by energy dispersive spectroscopy (EDS), phase analysis by X-ray diffraction (XRD), microhardness across the weldment by Vickers hardness tester and estimation of welding strength by dynamic mechanical analyser. Welding strength of around 34 MPa has been obtained and it is quite acceptable.