Paper AS-ThP6
Characterization of Laser-Treated Ti-6Al-4V-Surfaces

Thursday, October 25, 2018, 6:00 pm, Room Hall B

Lightweight Al, Mg, and Ti alloys are ubiquitous in aerospace and automotive applications. When these alloy materials are joined, either to similar or dissimilar materials, the chemical and physical state of the surface determines the quality of the bond. Methods for cleaning (chemical) and texturing (physical) metal alloy surfaces prior to joining or paining have traditionally relied on aggressive chemicals that are now considered environmentally unfriendly. Costs for adequately protecting of worker and protecting the environment are high enough that alternate surface processing methods are needed. During the last two years ORNL, began a systematic study of a unique laser processing method for both cleaning and texturing metal surface simultaneously. This novel surface treatment method uses laser interferometry produced by two beams of a pulsed Nd:YAG laser. Operating at 10Hz of frequency, this technique has been used to clean aluminum surfaces, and at the same time creating periodic and rough surface structures. Preliminary results for the Al-alloy laser-based surface treatment process were reported last year at this conference. One of the primary findings for Al-alloy surfaces was the development of an enhanced oxide surface region. Influence of the enhanced oxide on both adhesive joining and corrosion protection are now underway. Recently, we have extended these laser-processing studies to Ti-6Al-V4 (Ti64) alloys, which are widely used in the aerospace industry. Ti64 alloy surfaces can be cleaned using high-energy laser pulses (nanoseconds to milliseconds range) and, as with the Al-alloys, is accomplished mainly by surface melting and ablation. Our method is non-contact, does not rely on surface abrasion and significantly reduces the chemical impact of commonly used solvents and detergents. The process being optimized at ORNL uses a 2-beam method that not only cleans the surface for joining but textures the surface in a periodic manner. This poster present preliminary surface characterization results for the cleaning of Ti64-alloy surfaces. Results from scanning transmission electron microscopies, x-ray photoelectron spectroscopy, and contact angle measurements on as received and laser–treated commercial Ti64-alloy surfaces will be presented. This abstract has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy.