High cycle fatigue of laser beam deposited Ti-6Al-4V and inconel 718

Abstract

Laser Beam Deposition (LBD), or also called Laser Engineered Net Shaping (LENS), is used for fabrication and repair of metallic aerospace components. Basic research and process development have already been done on Ti-6Al-4V and the interest is now expanding to other aerospace alloys. For application of the technology on critical aircraft and engine parts, the status of the technology has to be assessed. Two identical components have been defined by NLR and fabricated at Optomec by the LENS™ technique. The components have been made with standard process parameters. One component was made of Ti-6Al-4V and the other one of Inconel 718. The components were given a standard heat treatment prior to cut-up for machining the test samples. Test samples were cut from the laser track and build directions to examine the tensile properties and the microstructure for both orientations. High cycle fatigue (HCF) tests were performed on round samples to create a stress vs. cycles curve for both alloys. Both components contained many macro and micro defects, such as large cavities, lack of bonding between layers and porosity. The fatigue performance of the laser deposited Ti-6Al-4V is better than of wrought material. Although the presence of pores decreases the performance, making the fatigue performance similar to wrought Ti-6Al-4V. The fatigue performance of Inconel 718 is similar to wrought material, even though the material contains a lot of small pores. Lack of bonding between layers decreases the fatigue performance of Inconel 718 accordingly. © Springer Science+Business Media B.V. 2009.