Titanium Alloy Repair with Wire-Feed Electron Beam Additive Manufacturing Technology

Abstract

Wire feeding can be combined with different heat sources, for example, arc, laser, and electron beam, to enable additive manufacturing and repair of metallic materials. In the case of titanium alloys, the vacuum operational environment of electron beam systems prevents atmospheric contamination during high-temperature processing and ensures high performance and reliability of additively manufactured or repaired components. In the present work, the feasibility of developing a repair process that emulates refurbishing an “extensively eroded” fan blade leading edge using wire-feed electron beam additive manufacturing technology was examined. The integrity of the Ti6Al4V wall structure deposited on a 3 mm thick Ti6Al4V substrate was verified using X-ray microcomputed tomography with a three-dimensional reconstruction. To understand the geometrical distortion in the substrate, three-dimensional displacement mapping with digital image correlation was undertaken after refurbishment and postdeposition stress relief heat treatment. Other characteristics of the repair were examined by assessing the macro- and microstructure, residual stresses, microhardness, tensile and fatigue properties, and static and dynamic failure mechanisms.

Wire-Based Additive Manufacturing of Ti-6Al-4V Using Electron Beam Technique

“…Since aluminum is the element in Ti-6Al-4V with the highest saturated vapor pressure, it can be expected that it has a significant tendency to evaporation and vaporization loss during processing. The evaporation of aluminum by processing Ti-6Al-4V with different AM processes has already been reported in the literature (i.e., EBF 3 [4,52], E-PBF [53,54], or L-PBF [55]). Unlike L-PBF, the excessive aluminum loss was reported for vacuum based processes E-PBF (up to 30%) and EBF 3 (up to 39%) by Juechter et al [54] and Xu et al, respectively [4].…”

“…Partial melting of the substrate by the electron beam is required to form the desirable liquid metal bridge material transfer mode between substrate and wire [70,71]. Tang et al [13] investigated the heat transfer in EBF 3 and simulated fluid flow of the weld pool by a 3D transient model. In EBF 3 the high temperature region is restricted to the area of a direct electron beam exposure, showing a steep temperature gradient to its surrounding.…”

“…Even when recent models also take the spreading of the weld bead into previously deposited bead and thus changing the geometry, the transferability on weld deposits produced by EBF 3 is questionable. In EBF 3 , unlike GMAW processes, the material-and energy input is decoupled and material transfer modes, but also heat source models, differ.…”

“…Recent literature [3,4] is limited for electron beam additive manufacturing, where the emphasis is mainly on material properties and microstructural details, and not on the process and parameter selection itself. The present study aims to establish suitable parameters for the EBAM process in α + β titanium alloy Ti-6Al-4V and determine the influence of these parameters on the dimensions of the single and multi-tracks welds for building walls with an optimal sequence of building.…”

“…Wire-based DED processes widen the field of application and have received considerable attention due to printing of more volumetric structures with simultaneous high deposition rates. Electron beam freeform fabrication (EBF³, EBF3, or EBFFF) is based on a wire feed DED-process using the electron beam as heat source and the suitability for processing titanium has already been demonstrated [ 2 , 3 , 4 , 5 ]. Since electron beam technique is based on a vacuum atmosphere (<5 × 10 −3 mbar), it is suitable to process reactive materials like titanium.…”