Evaluation of electron beam wire-fed deposition technology for titanium compressor blade repair

Abstract

In this research, two Ti‐8Al‐1V‐1Mo compressor blades with approximately 20,000 h of service were repaired using electron beam wire-feed (EB-WF) additive manufacturing (AM) technology. Ti‐6Al‐4V wire was used as the feedstock to fabricate layer-by-layer a thin-walled structure on the worn blade. The repaired compressor blades were inspected to examine the residual stresses, distortion, microstructure, chemistry, and mechanical properties with special attention given to characterize the interfacial zone between the dissimilar titanium alloys. The distortion after the repair was limited to ± 0.1 mm on the leading edge just adjacent to the interface, which shows the good potential of the developed method for repair applications. The different microstructural regions, consisting of transient, steady-state, dilution, and heat affected zones, were thoroughly characterized using optical microscopy and correlated with the microhardness. The average Vickers hardness in the blade and repair were measured as 338 ± 6 Hv and 312 ± 7 Hv, respectively. To characterize the tensile properties, miniature tensile test specimens were extracted from the repair interface. The yield strength, ultimate tensile strength, and elongation at break of the tested miniature specimens ranged between 869 and 906 MPa, 925–956 MPa, and 10–11 %, respectively. The tensile results were compared to similar literature studies and related standards. All specimens met the minimum requirement of AMS 4911 P wrought specifications, indicating the sound mechanical integrity of the repair. Fractography analysis showed that failure occurred in the repair section, which carries a high potential for maximizing the service life of the blade by allowing periodic repair and overhaul.