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The Effect of Discolouration in Cobalt Alloy Welding Rods on the Mechanical behaviour of the Welded Joints

Key Information

Academic supervisor: Dr Zak Abdallah, Industry supervisor: Mr Lester Madge

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This project will investigate the effect discolouration on welding rods has on the overall mechanical behavior, microstructure and chemistry of the welded joint. A wide range of colours have been observed on 3.2mmØ Cobalt-6 welding rods from straw, through gold to blue/dark purple and eventually grey, due to the nature of the process used. Three typical colours have been chosen for the purposes of investigation, namely: straw, gold and dark blue/purple. It has been observed on some occasions that when the different coloured rods have been used the perceived weldability can vary resulting in changes in performance, possibly due to changes in the microstructure and/or oxide characteristics. However, in some applications satisfactory performance has been noted.

Project Aims:

It is believed that the rods are the same chemistry regardless of the colour. However, the chemistry of the oxides developing on such rods has never been investigated. The aforementioned outcomes have made this project open for investigation. The sponsor company, Weartech International, will supply various discoloured rods (these will be cut accordingly to a typical length of 10mm and delivered to Swansea University). Also, the chemistry of the substrate rods will be supplied as a reference. The student will investigate:

1. The microstructure of each discoloured rod utilising a suitable etchant for the supplied material (alloy composition is required at this stage to save time).
2. The chemistry of the oxide layer utilising advanced methods e.g. Energy-dispersive X-ray spectroscopy (EDS).
3. The hardness from the top surface of the oxide layer to the substrate material of the rod.
4. The relation between the drawing rate and cooling speeds of the welding rods and the discolouration effects.
5. The relation between the drawing rate vs. hardness (for each discoloured rod).
6. The relation between the cooling rate vs. hardness (for each discoloured rod).
7. The relation between the melt temperature during boiling vs. hardness and colour (for each batch).
8. The relation between the drawing and cooling rate vs. % elements in each rod.
9. The exact melting point of discoloured rods using a differential scanning calorimetry device (DSC) – the discolouration might affect the melting point during welding. Therefore, this may give a relation between colour and the melting point of the rod.

At the end of the project, it is expected to have a better understanding of the possible effects of a range of oxide discolouration and their interrelationship with the welding rod chemistry and/or microstructure on weldability. The project will also derive useful relations between the key variables during manufacturing, on one hand, and the nature of discolouration, on the other hand. This project will also provide an opportunity for the potential student to gain hands-on experience in materials preparation, investigation and critical thinking related to the manufacturing process utilised.

Before submitting an application for the project, please see our Hints & Tips document which can be found here.

Sponsoring Company Weartech International
Company Website Eligibility

We welcome applications with Materials Science & Engineering preferred, but other physical sciences accepted (Engineering disciplines, Physics, Chemistry), 2.1 or 1st class degree preferred, or equivalent relevant experience that would enable the candidate to fulfil the role.
Normally, we would expect candidates to have met the University’s English Language requirements (e.g. IELTS 6.5 overall with 5.5+ in each component) by point of application.
Full eligibility can be found at https://www.materials-academy.co.uk/eligibility


Fees at Home / EU rate, and Stipend £12500, both for the period of one year.
For full details on funding eligibility, please refer to the Materials and Manufacturing Academy (M2A) Website.
Due to funding restrictions, this scholarship is not open to ‘International’ candidates.

Closing Date 5 April 2021

Start Date October 2021

Download Application Pack

Applications and informal enquiries about this studentship should be directed by email to: M2A@swansea.ac.uk