Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Materials researchers micromanage atoms in hard metal

14.06.2010
Drilling bits in the mining industry and cutting tools for metalworking in the manufacturing industry are often made of hard metal – a material nearly as hard as diamond.

Researchers have long tried to control the manufacturing process for the material to be able to steer in detail the hardness and other key properties to make it more durable. By combining theory and experiments, researchers at Chalmers University of Technology in Sweden have now taken a crucial step toward being able to micromanage the performance of the material, down to the level of the atom.

“The size of bore can vary, from a diameter of 10 meters for large tunnel bores down to three hundredths of a millimeter, thinner than a human hair, for applications in the electronics industry. This places great demands on the manufacturing process to attain precise properties. The results of Sven Johansson’s and Jonathan Weidow’s research are of great interest to industry, and what they have managed to do is unique,” says Göran Wahnström, professor of physics.

Hard metal is a mixture of a hard carbide phase, wolfram carbide (WC), and a tougher metal phase, cobalt (Co). It is produced by sintering, whereby fine powders of WC and Co are heated up so the cobalt melts and the material is pulled together by capillary force. The result is a solid material consisting of a hard skeleton of wolfram carbide grains surrounded by the tougher cobalt-rich cement phase.

The size of the wolfram carbide grains is key to the hardness of the hard metal. The great challenge is to be able to control the growth of these grains during the sintering process. By combining experimental and theoretical methods, the researchers now understand how they can control the structure of the material in detail, down to the level of the atom, during the production process. The work was carried out as a twin doctoral project with funding from the Swedish Research Council and the industry (Sandvik and Seco Tools) and in collaboration with a research team in Grenoble.

“Our work has focused on characterizing and understanding the interfaces in the material, on the one hand between the wolfram carbide grains, so-called granular interfaces and, on the other hand, between the wolfram carbide grain and the cementing phase, what are called phase interfaces. The theoretical part made use of quantum mechanical density-functional theory to describe and understand how the electrons in the material bind together the material,” says Göran Wahnström.

By doping the material (adding another substance in tiny portions) scientists have known that the growth of the grain can be dramatically limited. A tiny addition of vanadium can limit the growth of the grains to one tenth, from a particle size of one thousandth of a mm down to one ten-thousandth mm. But they did not know why.

In the doped materials, the research group in Grenoble found, using high-resolution electron microscopy, that an extremely thin layer, only two atom layers thick, of a cubical structure can be built on the wolfram carbide grains. At Chalmers, Jonathan Weidow used atom-probe tomography, a technology unique in Sweden, to analyze the interfaces atom by atom.

“These films can affect the growth, but the question is whether they are there during the actual sintering process when the WC particles are growing, when the experimental microscopy technology cannot be used. The theoretical prediction is that these films can also exist at the high sintering temperatures. Large grains with the composition of the film are then thermodynamically unstable, but the thin film is stabilized by strong bindings on the interface between the film and the cementing phase,” says Göran Wahnström.

Sven Johansson’s dissertation is titled A computational study of interface structures and energetics in cemented carbides and steels.

Jonathan Weidow’s dissertation is titled Effect of metal and cubic carbide additions on interface chemistry, phase composition and grain growth in WC-Co based cemented carbides

Contact:
Sven Johansson, Division of Material and Surface Theory; sven.johansson@chalmers.se. Tel. +46 (0)31-772 3669

Jonathan Weidow, Division of Microscopy and microanalysis; jonathan.weidow@chalmers.se. Tel. +46 (0)31-772 3137

Supervisors:
Göran Wahnström, +46 (0)31-772 3634
Hans-Olof Andrén, +46 (0)31-772 3309
Pressofficer Åsa Ekvall:Phone +46(0)31-772 4891; mail: asa.ekvall@chalmers.se

Åsa Ekvall | idw
Further information:
http://publications.lib.chalmers.se/cpl/record/index.xsql?pubid=119780
http://publications.lib.chalmers.se/cpl/record/index.xsql?pubid=121196

More articles from Machine Engineering:

nachricht Scientists from Hannover develop a novel lightweight production process
27.09.2017 | IPH - Institut für Integrierte Produktion Hannover gGmbH

nachricht PRESTO – Highly Dynamic Powerhouses
15.05.2017 | JULABO GmbH

All articles from Machine Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Los Alamos researchers and supercomputers help interpret the latest LIGO findings

18.10.2017 | Physics and Astronomy

Study shows how water could have flowed on 'cold and icy' ancient Mars

18.10.2017 | Physics and Astronomy

Navigational view of the brain thanks to powerful X-rays

18.10.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>