In this interview, Michael Davies from Micro Materials Ltd (MML) talks about the importance of high-temperature nanomechanical testing for a variety of industries, and how the NanoTest can help researcher and engineers characterize the mechanical and tribological properties of their materials at elevated temperatures.
WS: Please can you give us a brief introduction to nanomechanical testing.
MD: Nanomechanical testing describes a wide range of experimental techniques which are used to probe the mechanical properties and tribological behaviour of thin films, coating systems and small volumes of material.
The test techniques used by the NanoTest are based on depth sensing indentation technology originally used to make nanoscale impressions in materials to determine properties such as hardness and Young’s modulus without the need for optical imaging.
Over time, additional capabilities such as scratch and wear testing, high strain rate impact testing and fretting have been developed, to allow researchers to examine a wider range of behaviour.
WS: Why is testing at high temperatures important?
MD: Testing at elevated temperature allows the researcher to gain insight into their materials’ behaviour in relevant working conditions.
Across a wide range of applications, it has been demonstrated that room temperature testing alone cannot give the full picture the way a coating system or material will behave at operating temperatures. Extrapolation from room temperature data can often give a poor indication of in-service properties which will directly affect performance.
As a result, high temperature testing has become an invaluable tool for researchers working in many areas allowing them to obtain reliable data for performance prediction.
The next generation of aerospace materials will have to operate at ever higher temperatures, making mechnical testing at elevated temperatures crucial. Image credit: Shutterstock/superjoseph
WS: What properties of materials are affected most drastically by temperature?
MD: Changes in temperature can affect a wide range of mechanical properties. Typically the greatest changes are seen in the hardness, Young’s modulus and creep behaviour, although it depends on the materials. These changes in mechanical properties have a knock-on effect on the wear behaviour of those materials.
WS: What applications/industries is this most relevant for?
MD: In many sectors, there is a big push to find the next generation of materials which will enable improved efficiency or additional capabilities. For industries such as power generation, high speed machining and aerospace, this means developing materials which can operate at higher temperatures.
These industries represent some of the most extreme temperature requirements out there, anything up to 1000˚C and above. In other applications, such as lead free solder development, microelectronics, and polymer research, the temperature requirements are not as severe, but elevated temperature behaviour is just as relevant.
WS: How does your NanoTest platform help with this type of elevated-temperature testing?
MD: The NanoTest allows researchers to explore mechanical properties and tribological behaviour at temperatures up to 850˚C. Our high temperature test capability has been proven to allow experimentation even at the highest temperatures without sacrificing data quality and reliability.
Elevated temperature tests are not limited to indentation - we also offer a full range of nanomechanical test techniques at high temperature, including scratch and wear and high strain rate impact testing.
This capability is supported by the track record of peer reviewed scientific publications produced by researchers using the NanoTest. We have the highest number of publications at elevated temperature, and also the highest ever published temperature for nanomechanical testing at 750˚C.
The NanoTest from Micro Materials
WS: What are the main advantages of the NanoTest compared to other instruments?
MD: Micro Materials have pioneered high temperature nano-mechanical testing since its earliest days, making the company experts in this area. The unique design of the NanoTest means that we can achieve industry leading low levels of thermal drift, critical to measurement reliability, even at the highest operating temperatures.
This stability is built on the fundamental design of the instrument, but also the research and development into high temperature test techniques that the company has done over the last 15 years. This has led to improvements such as independently heated samples and probes to ensure isothermal contact, and a patented control algorithm which allows all our users to achieve the highest possible levels of measurement reliability.
We have also in recent years developed a vacuum instrument which allows us to push the temperature envelope even higher, currently allowing reliable measurements to 850˚C, the highest temperature available for this type of instrument.
WS: Can you give us an example of a study where one of your customers was able to achieve superior results thanks to the NanoTest?
MD: In some work from the University of Oxford recently publicised in Materials World, Dr David Armstrong was able to use the NanoTest to examine the properties of irradiated materials for Generation IV nuclear reactor research at relevant reactor operating temperatures.
This involved using the NanoTest to obtain mechanical properties as a function of depth into the irradiated surface at temperatures up to 750˚C. This is just one example of how the NanoTest is aiding researchers trying to meet the material demands of modern industries.
WS: How do you think the high-temperature testing field will move forward in the next few years?
MD: In many industries, ongoing development in this area is primarily focussed on pushing the operating environment to even greater extremes of temperature. To meet this goal we are continually working to allow researchers to perform experiments at even higher temperatures.
We are already in the process of testing the hardware required to extend the testing window up to 1000˚C, and anticipate release of this capability during 2016. In the future we will work to further extend both the temperature and the range of test techniques available to meet researchers developing needs.
About Michael Davies
Michael graduated with a degree in Physics at the University of Nottingham, and went on to complete a PhD focusing on the characterisation of the mechanical properties and creep behaviour of power station structural materials at their operating temperatures using high temperature nanoindentation technques.
He joined MML in 2011, bringing a wealth of high temperature experience and knowledge to the existing applications team. Since joining MML, Mike has worked on a wide range of projects and developments further expanding his nanomechanical testing expertise.
For more information about the NanoTest, download the PDF brochure, or visit the Micro Materials website.
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