Towards the perfect neck for HPHT PCD
Lead Research Organisation:
University of Oxford
Department Name: Materials
Abstract
Differences in the microstructure of PCD have an enormous influence on cutter life. Although there are many suggestions, concrete evidence for which factors are most important is limited. As a result, there is no clear understanding of what the optimum microstructure should be for a given drilling region and therefore no clear direction for the future development of processing.
An important example is the effect of grain size. Fine grained PCD has excellent wear resistance compared with coarser grained grades but tends to undergo catastrophic failure well before the diamond table has worn away to a great extent. Conversely, coarser grades wear more quickly but are less prone to fracture. This suggests an inverse relationship between damage tolerance and wear resistance. However, all microstructures do not plot on the same line of wear resistance against damage tolerance. The ambition is to understand the factors that move PCD towards the top right hand corner of such a plot, i.e. high wear resistance and long life in service, and hence to be able to tailor the microstructure to achieve this in different conditions.
There is now a reasonably rich literature concerning (i) the general processes occurring during service and (ii) the room temperature, monotonic mechanical properties of PCD. However, (i) suggests that both high local temperatures during service (which could cause graphitisation, modification of residual stresses or of innate properties) and gradual damage accumulation are important, which is entirely inconsistent with the conditions of the laboratory work in (ii). In addition, it is thought that subtle differences in processing conditions have a significant effect (e.g. different manufacturers' apparently similar products give different results in different environments).
It is evident from the above that there is room for a materials science investigation of processing/composition/heat treatment-microstructure-property relationships but, in contrast to much previous work, focusing on the conditions of importance to the application such as mechanical properties at the temperatures encountered in service (~ 800 C) and cyclic loading. In addition, state-of-the-art electron optical and other characterisation techniques, using Oxford's extensive range of equipment and expertise, will be used to investigate the differences in microstructure caused by processing variations and subsequent heat treatment and deformation.
Research Areas: "Manufacturing Technologies" and "Materials Engineering - Ceramics" in the Manufacturing the Future Theme.
An important example is the effect of grain size. Fine grained PCD has excellent wear resistance compared with coarser grained grades but tends to undergo catastrophic failure well before the diamond table has worn away to a great extent. Conversely, coarser grades wear more quickly but are less prone to fracture. This suggests an inverse relationship between damage tolerance and wear resistance. However, all microstructures do not plot on the same line of wear resistance against damage tolerance. The ambition is to understand the factors that move PCD towards the top right hand corner of such a plot, i.e. high wear resistance and long life in service, and hence to be able to tailor the microstructure to achieve this in different conditions.
There is now a reasonably rich literature concerning (i) the general processes occurring during service and (ii) the room temperature, monotonic mechanical properties of PCD. However, (i) suggests that both high local temperatures during service (which could cause graphitisation, modification of residual stresses or of innate properties) and gradual damage accumulation are important, which is entirely inconsistent with the conditions of the laboratory work in (ii). In addition, it is thought that subtle differences in processing conditions have a significant effect (e.g. different manufacturers' apparently similar products give different results in different environments).
It is evident from the above that there is room for a materials science investigation of processing/composition/heat treatment-microstructure-property relationships but, in contrast to much previous work, focusing on the conditions of importance to the application such as mechanical properties at the temperatures encountered in service (~ 800 C) and cyclic loading. In addition, state-of-the-art electron optical and other characterisation techniques, using Oxford's extensive range of equipment and expertise, will be used to investigate the differences in microstructure caused by processing variations and subsequent heat treatment and deformation.
Research Areas: "Manufacturing Technologies" and "Materials Engineering - Ceramics" in the Manufacturing the Future Theme.
Planned Impact
Students: A CDT is first and foremost a training activity. The students will benefit from an interdisciplinary programme taught by leaders in their respective fields from our eight partner universities and industrial collaborators, focusing on the fundamentals of material science, from the classical to the quantum, but with an emphasis on diamond and related materials and application driven themes. Students will be recruited from a wide range of disciplines, maximising both quality and diversity to provide a richer experience. Our structure ensures that our students will experience at least three different research environments during their studentship; the PhD home university and two different partner institutes (of which one can be industry or that of our international academic partners). This greatly enhances the student experience, promotes mobility and encourages research across disciplines. When they graduate Diamond Science and Technology (DST) students, with a breadth of training no one institution could deliver alone will be ideally placed for employment in academia and industry. Our students will also be able to communicate across disciplines and make the required DST transformative breakthroughs in a wide range of societally important areas, e.g. electronics, optics, quantum computing, photonics, composite materials, energy efficiency and sensing.
Industry and Economy: Our industrial partners are focused on products, jobs and wealth creation. To achieve this they need appropriately skilled people and university R&D to sustain and grow their business in a world where competition is intense. The training programme has been devised to produce graduates who understand the interdisciplinary challenges faced and can communicate across fields, for employment in industries innovating in DST or other high performance material enabled products, businesses that exploit these materials or new businesses created. The industrial letters of support clearly demonstrate the demand for our students and the enthusiasm for the research. Market sectors such as electronics, photonics, sensors, defence and security, materials, abrasives, communications and healthcare will benefit. Through collaboration, industry will gain access to world-class academics and facilities. The training programme is also accessible to industrialists who will profit from accessing MSc modules. With the knowledge gained, companies will be able rapidly exploit DST technologies to position themselves at the cutting-edge. This CDT CDT will enable joined-up and efficient collaboration between universities, companies and users, greatly strengthening impact.
Society: Diamond is so much more than a gemstone. This CDT will actively drive DST in areas of huge societal impact such as, energy (e.g. efficient power devices, nuclear safety), the environment (e.g. decontamination, water quality monitoring), food safety (e.g. sensing contaminants) and health (e.g. ultra-high resolution functional imaging). Inside Science (11/7/13; www.bbc.co.uk/programmes/b036kxv8) very recently reported on the growing importance of DST to many aspects of modern society and highlighted the £20M Element Six Ltd investment in a new diamond research centre in the UK. We will ensure that DST is used to motivate school children via innovative approaches such as "How to grow a diamond" BBC Bang Goes the Theory, 2011, (>81,000 hits on www.youtube.com/watch?v=s8qgE4LkZa4). To bring diamond to the forefront of public attention we will showcase the work through exhibitions using thought provoking and fun demonstrations, host public understanding lectures, produce podcasts/videos about our work, and host an interactive web-based forum where people have an opportunity to contact "the scientist" in order to ask questions about DST. This is in addition to publishing the results of our research in leading scientific journals, at international conferences and through the DST CDT website.
Industry and Economy: Our industrial partners are focused on products, jobs and wealth creation. To achieve this they need appropriately skilled people and university R&D to sustain and grow their business in a world where competition is intense. The training programme has been devised to produce graduates who understand the interdisciplinary challenges faced and can communicate across fields, for employment in industries innovating in DST or other high performance material enabled products, businesses that exploit these materials or new businesses created. The industrial letters of support clearly demonstrate the demand for our students and the enthusiasm for the research. Market sectors such as electronics, photonics, sensors, defence and security, materials, abrasives, communications and healthcare will benefit. Through collaboration, industry will gain access to world-class academics and facilities. The training programme is also accessible to industrialists who will profit from accessing MSc modules. With the knowledge gained, companies will be able rapidly exploit DST technologies to position themselves at the cutting-edge. This CDT CDT will enable joined-up and efficient collaboration between universities, companies and users, greatly strengthening impact.
Society: Diamond is so much more than a gemstone. This CDT will actively drive DST in areas of huge societal impact such as, energy (e.g. efficient power devices, nuclear safety), the environment (e.g. decontamination, water quality monitoring), food safety (e.g. sensing contaminants) and health (e.g. ultra-high resolution functional imaging). Inside Science (11/7/13; www.bbc.co.uk/programmes/b036kxv8) very recently reported on the growing importance of DST to many aspects of modern society and highlighted the £20M Element Six Ltd investment in a new diamond research centre in the UK. We will ensure that DST is used to motivate school children via innovative approaches such as "How to grow a diamond" BBC Bang Goes the Theory, 2011, (>81,000 hits on www.youtube.com/watch?v=s8qgE4LkZa4). To bring diamond to the forefront of public attention we will showcase the work through exhibitions using thought provoking and fun demonstrations, host public understanding lectures, produce podcasts/videos about our work, and host an interactive web-based forum where people have an opportunity to contact "the scientist" in order to ask questions about DST. This is in addition to publishing the results of our research in leading scientific journals, at international conferences and through the DST CDT website.
People |
ORCID iD |
| Richard Todd (Primary Supervisor) | |
| Tuoran Chen (Student) |