Powder Metallurgical Processing For Graded Alloy Microstructures

The understanding of microstructures and their effect upon alloy properties is a key part of metallurgical processing as developers seek materials for harsh applications such as those found in the oil & gas, chemical and aeroengine industries. Enhancement of alloy performance has been achieved for ranges of alloys, including steels and nickel superalloys, by addition of minor elements and thermomechanical processing, thereby manipulating the chemistries and microstructures to provide desired benefits. However, such additions and processing steps are generally performed on bulk alloys, often resulting in undesirable costs in finished components arising from the presence of expensive elemental additions in areas where they serve no purpose. This is particularly the case with additions of precious metals (platinum, palladium, ruthenium etc.). Such issues can be circumvented, for example, by deposition of surface coatings. However, thin surface coatings can be subject to degradation by in-use environmental conditions, exposing the underlying unprotected alloy and shortening component lifetime.

In this project we will examine routes for generating asymmetric "graded" alloy microstructures to provide property enhancement at the surface of components, where they are needed, avoiding the cost of bulk alloying additions. Concentrating upon powder metallurgical processing to generate the graded microstructures, we will introduce precious metals into the surfaces of steels and nickel superalloys, examining the effect upon the microstructures, the interactions of the modified microstructures with the underlying base alloys, thermomechanical properties and corrosion resistance under environmental conditions relevant to the end-use applications of those alloys. The industrial partners, Johnson Matthey and Liberty Powder Metals, will work closely with the student to provide complementary manufacturing and characterization facilities, thereby allowing the successful student to gain experience of both base metal and precious metal-containing alloys.

The EPSRC Centre for Doctoral Training in Advanced Metallic Systems was established to address the metallurgical skills
gap, highlighted in several reports [1-3] as a threat to the competitiveness of UK industry, by training non-materials
graduates from chemistry, physics and engineering in a multidisciplinary environment. Although we will have supplied ~140
highly capable metallurgical scientists and engineers into industry and academia by the end of our existing programme,
there remains a demonstrable need for doctoral-level training to continue and evolve to meet future industry needs. We
therefore propose to train a further 14 UK based PhD and EngD students per cohort as well as 5 Irish students per
cohort through I-Form.

Manufacturing contributes over 10% of UK GVA with the metals sector contributing 12% of this (£10.7BN [4,5]) and
employing ~230,000 people directly and 750,000 indirectly. It is estimated that ~2300 graduates are required annually to
meet present and future growth [5]. A sizeable portion of these graduates will require metallurgical expertise and current
numbers fall far short. From UK-wide HESA data, we estimate there are ~330 home UG/PGT qualifiers in materials and
~35 home doctoral graduates in metallurgy annually, including existing AMSCDT graduates, so it is unsurprising that
industry continues to report difficulties in recruiting staff with the required specialist metallurgical knowledge and
professional competencies.

As well as addressing this shortfall, the CDT will also impact directly on the companies with which it collaborates, on the
wider high value manufacturing sector and on the UK economy as a whole, as follows:

1. Collaborating companies, across a wide range of businesses in the supply chain including SMEs and research
organisations will benefit directly from the CDT through:

- Targeted projects in direct support of their business and its future development and competitiveness.
- Access to the expertise and facilities of the host institutions.
- Involvement in the training of the next generation of potential employees with advanced technical and leadership skills
who can add value to their organisations.

2. The UK High-Value Manufacturing Community will benefit as the CDT will:

- Develop the underpinning science and advanced-level knowledge base required by future high technology areas, where
there is high expectation of gross added value.
- Provide an enhanced route to exploitation, by covering the full spectrum of technology readiness levels.
- Ensure dissemination of knowledge to the sector, through student-led SME consultancy projects, the National Student
Conference in Metallic Materials and industry events.

3. The wider UK economy will benefit as the CDT will:

- Promote materials science and engineering and encourage future generations to enter the field, through outreach
activities developed by the students that will increase public awareness of the discipline and its contribution to modern
life, and highlight its importance to future innovation and technologies.
- Develop and exploit new technologies and products which will help to maintain a competitive UK advanced
manufacturing sector, ensure an internationally competitive and balanced UK economy for future generations and
contribute to technical challenges in key societal issues such as energy and sustainability.

References:
1. Materials UK Structural Materials Report 2009
2. EPSRC Materials International Review 2008
3. EPSRC Materially Better Call 2013
4. The state of engineering, Engineering UK 2017
5. Vision 2030: The UK Metals Industry's New Strategic Approach, Metals Forum