Abstract
The laser-based treatment of a metal surface is an intrinsically non-chemical technique that can alter both the topology and chemistry of surfaces. A laser-based treatment for coating and joining applications can offer alternative surface preparations to the chemically-based surface preparation techniques, which are subject to severe environmental protection and hazardous-waste management considerations. In this study, the surface chemistry and sub-surface microstructural changes are investigated for a novel surface processing method using laser interferometry produced by two beams of a pulsed Nd:YAG laser. The two-beam laser-interference allowed the structuring of the surface at length scales much less than that of the laser beam spot. Surface chemistry changes in the oxide layer of AA 2024-T3 aluminum alloy rolled sheet due to laser processing were investigated using x-ray photoelectron spectroscopy (XPS). Near surface microstructural changes have been investigated with scanning electron microscopy and energy dispersive x-ray spectroscopy (SEM/EDS), and scanning transmission electron microscopy (STEM) as a function of number of interfering laser shots. SEM microstructure pictures of the top surface shows the minimization of surface defects, as all of the sharp features from a rolled sheet surface were smoothed by laser-structuring. STEM images indicate that the laser-interference processing reduced the formation of CuMn-rich precipitates over a 500–800 nm depth from the top surface. XPS data indicated that the Al oxide layer is modified compared to that of the baseline specimen and that the oxide thickness increases with the number of shots per spot. The additional thicker oxide on Al alloys is expected to increase the corrosion resistance of the coated Al 2024.
Original language | English |
---|---|
Article number | 106457 |
Journal | Optics and Laser Technology |
Volume | 131 |
DOIs | |
State | Published - Nov 2020 |
Funding
This research was conducted at UT-Battelle, LLC, for the project “Laser-Interference Surface Preparation for Enhanced Coating Adhesion and Adhesive Joining of Multi-Materials.” This project, WP-2743, has been funded by the Strategic Environmental Research and Development Program (SERDP) Weapon Systems & Platforms 4800 Mark Center Drive, Suite 17D03, Alexandria, VA 22350-3605. The authors acknowledge the following technical support: Dr. Michael Lance of ORNL for providing useful guidance on profilometry, Dana McClurg of ORNL for conducting the profilometry measurements; Tom Naguy, Deputy Technical Director, Air Force Materiel Command, W-P AFB; Michael Casey Jones, Materials Engineer, W-P AFB; Rick Osterman and Stan Bean of M&P Solutions LLC, Pahrump, NV for guidance on aerospace applications. This research was conducted at UT-Battelle, LLC, for the project “Laser-Interference Surface Preparation for Enhanced Coating Adhesion and Adhesive Joining of Multi-Materials.” This project, WP-2743, has been funded by the Strategic Environmental Research and Development Program (SERDP) Weapon Systems & Platforms 4800 Mark Center Drive, Suite 17D03, Alexandria, VA 22350-3605 . The authors acknowledge the following technical support: Dr. Michael Lance of ORNL for providing useful guidance on profilometry, Dana McClurg of ORNL for conducting the profilometry measurements; Tom Naguy, Deputy Technical Director, Air Force Materiel Command , W-P AFB; Michael Casey Jones, Materials Engineer, W-P AFB; Rick Osterman and Stan Bean of M&P Solutions LLC, Pahrump, NV for guidance on aerospace applications. Notice : This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).
Keywords
- Aluminum
- Dissolution
- Interference
- Laser
- Microstructure
- Precipitates