Effect of Surface Texture on the Adhesion Performance of Laser Treated Ti6Al4V Alloy

Abstract

The growing demand in lighter and safer structures generates the requirement of lighter joining strategies, particularly for lightweight metal alloys, composites, and also joining dissimilar materials together. Titanium alloys stand out as the conventional choice for materials for light weight structures. Adhesive bonding of titanium is an appealing route for joint design, also for the possibility of joining it with dissimilar materials. The realization of a strong joint depends not only on the joint design and type of adhesive, but also on the preparation of the adhering surface. Laser texturing presents advantages compared to common surface preparation processes in terms of eco-compatibility, energetic efficiency, ease of manufacturing, and repeatability. This work presents a preliminary investigation on laser texturing of Ti6Al4 V alloy with a pulsed fiber laser source with the aim to increase surface adhesion for bonding. Particularly, different surface textures are proposed, and laser machining strategies are developed. The results showed that laser texturing provided up to eightfold and 30% higher shear strength compared to plain and sand blasted surfaces, respectively. Failure analysis showed that a margin of improvement is still possible by adapting the surface texture for better cavity filling and reducing surface damage caused by the laser treatment.

Improving adhesion of copper/epoxy joints by pulsed laser ablation

“…Therefore, the improvement in adhesive bonding after PLA is attributed to the increase in surface area, the generation of surface features, also of sub-micron scale, which improved wetting and acted as locking sites enabling mechanical interlocking [8,9,12,14]. It has been observed in previous related work that all these effects combined may also lead to the formation of a composite interfacial region (i.e.…”

“…9(h) and (i) that surface morphology of the detached oxide layer closely resembles that observed in the SEM pictures reported earlier in the paper. Notice that failure of the laser generated oxide layer was also observed in titanium alloys [9].…”

“…On top of this, PLA improves bond repeatability, as well as waste and cost reduction, and is also prone to automation. Previous literature works have indicated that PLA promotes significant modifications of surface morphology [8,9] and chemistry [10,11], leading to improvement in surface wetting [12,13] and mechanical interlocking [12,14], with consequent increases in bond toughness [15,16] and long term joint stability [18]. It may also outperform traditional joining techniques, such as riveting and fusion welding when dealing with dissimilar materials [19].…”

Influence of Adherend Surface Roughness on the Adhesive Bond Strength

“…In order to get a strong and durable bonded joint, a surface treatment of adherends should ensure the following aspects: removal of all contaminants (lubricants, dusts, loose corrosion layers, micro-organisms) from the surfaces (da silva et al, 2009), good surface wettability (Encinas et al, 2012;Sedev et al, 2014), surface energy (Guzanova et al, 2014;Islam et al, 2014), good activation of surfaces of elements being bonded (Encinas e al., 2014) etc. There are different chemical and physical surface treatments available, but proper selection of surface treatment is very important (Rotella et al, 2016;Williams et al, 2014;Maressa et al, 2015).…”

Surface modification of Ti6Al4V alloy by pulsed Yb-laser irradiation for enhanced adhesive bonding

“…These observations suggest that the resulting oxide layer might be easily detached from the substrate and could affect the overall mechanical response of T-peel joints. The issue associated to surface induced damage following laser irradiation was also discussed in a recent related work [18].…”