Machining of hard metal alloys such as Ti6Al4V alloys with cutting tools incurs high cost particularly in the replacement of worn out tools. In light of this, lasers offer a non-contact processing method which could potentially reduce costs. Lasers can introduce undesirable processing effects, but with the emergence of high powered ultrashort lasers, these processing defects can be greatly reduced. To date, there have been limited studies conducted within the area of picosecond laser machining process. This research has two primary objectives. Firstly, using lasers as an alternative to mechanical processes. Secondly, using a picosecond laser in machining of Ti6Al4V alloy to maximise material removal rate and minimise defects. In this study, an Nd:YVO4 Edge wave picosecond pulsed laser was used for machining Ti6Al4V alloy in air and at room temperature and pressure to understand laser interaction with the Ti6Al4V alloy. The laser was rated at 300W with up to 20 MHz repetition rate and up to 10 m/s scanning rate. Design of experiments was used to understand the effects of varying laser parameters and establishing the ablation threshold. Once the process parameters were established, the next stage was aimed at improving the material removal rates through various strategies. To understand the material removal process, a state of the art holography method was utilised to visualise the laser material interaction. This research has produced three significant results. It was established that the ablation threshold was 45 mJ/cm2 for picosecond laser machining of Ti6Al4V alloy. For the first time in this field of research, the optimal material removal was achieved when the laser was focused at 15 mm above the sample surface resulting in an improvement from 0.1 to 0.6 mm3/min. The holography visualisation revealed that the material removal rate was significantly reduced as the number of pulses increased due to the presence of plasma. Findings of this research support the future of picosecond laser machining of hard metals for micro as well as macro scale applications. Some of the relevant industries for this area of research include aerospace manufacture, automotive parts manufacturing and even manufacture of personal items such as watches, eye wear and jewellery.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:727972 |
| Date | January 2017 |
| Creators | Bin Ahmad Sabli, Ahmad Syamaizar |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/ultrashort-pulsed-laser-machining-of-ti6al4valloy(a01ab696-e895-431c-944d-1c7cd94420f5).html |
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