High-deposition-rate processing of Ti-6Al-2Sn-4Zr-2Mo by wire-arc directed energy deposition: Microstructural and high-temperature properties

The current study aims to increase the deposition rate of Ti-6Al-2Sn-4Zr-2Mo-0.1Si (Ti-6242) wire using cold metal transfer welding in wire-arc directed energy deposition (waDED). A deposition rate of 1.8 kg/h was achieved, surpassing the current state of the art, ∼0.6 kg/h, for Ti-6242 in waDED. Microstructural characterization revealed a fine α+β microstructure within columnar prior-β grains, averaging ∼500 μm. The α-phase shows lamellar morphology. Tensile testing was conducted at three distinct temperatures. At room temperature a tensile strength of 1020 MPa and an elongation at fracture of 7.3% was reported. Increasing temperatures to 300 and 550 °C led to a decrease in ultimate strength and an increase in ductility. Creep testing was conducted at 550 °C, 575 °C and 600 °C, at a constant load of 210 MPa. Minimum creep rates achieved were below 1 x 10−7s−1. The calculated activation energy was 380 kJ/mol. Based on this value; the active creep mechanism was inferred to be dislocation climb assisted by diffusion. Mechanically, the deposited material did not present any critical defects or early failures and achieved equivalent or superior properties to wrought and other additively manufactured Ti-6242. However, some anisotropic features were identified throughout mechanical testing. The results obtained in this study confirm that the conventional alloy Ti-6242 can be processed by waDED at high deposition rates and achieve reproducible properties, enabling cost and environmental savings for high-temperature aerospace or stationary turbine applications.