Investigations into the effects of electron beam welding on thick Ti–6Al–4V titanium alloy

Abstract Electron beam welding (EBW) of titanium alloy Ti–6Al–4V is not an easy task and finding the correct welding parameters is one of the critical activities when the product is intricate in shape. The procedure adopted to weld 17.5 mm thick joint in a spherical titanium gas bottle using EBW is presented here. Available EBW machine was capable of welding full penetration joint only up to 12.5 mm in titanium. Single sided partial penetration weld yielded poor result in production welding due to repeated defects like lack of fusion, root porosities, weld bead depression, under cut, etc. A two-pass double side welding technique was developed, and a joint thickness of 21 mm was decided so that a partial penetration weld can be attempted with lesser beam power. The extra material kept at the root of the weld can be machined off after welding. Single pass was made from one side of the joint producing a partial penetration weld with a penetration of nearly 19 mm. The second pass was made from the reverse side of the joint producing a similar partial penetration weld with almost the same penetration as that of the first weld. Trial welds were carried out and considerable difficulties were encountered in developing the welding procedure for establishing a defect free weld. Fusion zone voids and root porosities were observed and techniques were developed which eliminated their occurrence. Systematic weld qualification was carried out on coupon level and mechanical property and microstructure evaluations were carried out to ensure the joint integrity. Based on the technology developed and parameters arrived, the final specimen was welded. After passing through non-destructive tests, it was subjected to hydraulic proof pressure test with strain gauges and acoustic emission sensors for validating the capability of the technology developed. It has qualified all the test requirements as per the specifications and has been used for aerospace applications.