Use this URL to cite or link to this record in EThOS:
Title: Laser surface texturing of titanium alloy for improved wettability properties
Author: Rico Sierra, David
ISNI:       0000 0004 9359 1988
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2020
Availability of Full Text:
Access from EThOS:
Access from Institution:
Surface texturing of different types of materials has been explored through the years with the aim of modifying the intrinsic properties of such material surfaces. A wide range of surface texturing processes has been developed for the manufacturing industry, always looking to improve the quality of the final results while reducing the associated costs. Surface structuring processes for the modification of the wettability properties of the materials has been one of the most explored subjects in this area. This type of surface modification is mostly aimed at inducing high water repellence capabilities for different purposes such as self-cleaning and anti-icing. Development of this type of surfaces usually required the creation of micro and nanoscale feature in the material surface, however, surface micromachining processes have been always a challenging subject due to the scale of the required work, increasing the required manufacturing complexity and production costs. Laser surface texturing has gained popularity in the micromachining surface processing due to being an accurate and highly controllable process capable of producing surface features in nano and micro scales. The use of ultra-short pulsed lasers with pulse durations in the range of femto and picoseconds have been capable of producing incredibly accurate results on the creation of surface features in these scales giving a significant advantage compared with traditional processes. On the other hand, the complexity of these types of laser systems and the low throughput capabilities have limited their use to mainly research purposes. The introduction of robust nanosecond pulsed fibre lasers has opened a window of opportunity for the development of surface texturing processes with flexible and almost maintenance-free equipment suitable for the manufacturing industry. Due to the longer pulse duration, this type of laser systems are only capable of creating surface features in microscale producing significant thermal effects compared with ultra-short pulsed lasers. The main aim of this thesis is to develop a surface structure capable of modifying the wettability properties of Ti-6Al-4V and thus develop a super-hydrophobic effect with the use of a nanosecond pulsed fibre laser. A comprehensive study to understand the ablation mechanism of Ti-6Al-4V using the nanosecond pulsed fibre laser was carried out for a single pulse ablation process. The results reveal the effects of duration and temporal pulse shape in the ablated craters on the titanium alloy, showing a direct correlation between the amount of removed and molten material produced by the laser ablation process. These results provided a map of suitable parameters for the surface structuring process. The creation of micro-pillar like surface structures through laser ablation showed to be beneficial for the development of a super-hydrophobic state of the titanium alloy surface. Molten material deposition due to the thermal component of the nanosecond pulsed laser was beneficial for the development of super-hydrophobic surfaces with static contact angle ≈ 163° . A thermal post-processing was carried out for the improvement and stabilisation of the oxidation created on the surface by laser ablation developing the super-hydrophobic behaviour in the created micro-structure. Surface nano-structures induced by a picosecond laser were produced on top of the micro-pillars showing improvements of the super-hydrophobicity state of the surface structure. Alternative single laser surface structures were created with different pulse durations (in the nanosecond regime) in order to emulate the induced nano-structures. These structures displayed super-hydrophobic effects increasing the static contact angle to ≈ 168° and contact angle hysteresis under 10° clearly displaying high water repellency capabilities.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral