The Evolution of Tools

Since our hunter-gatherer ancestors first fashioned spears out of rock, there’s been an unending quest to build better tools. In fact, human advancement has been marked by its mastery of the materials necessary to do just that. The harnessing of metal led the way out of the Stone Age, with the discovery that copper–and later, bronze and iron–could be forged into tools and implements.

For centuries, diamond has been prized for its mechanical properties. Researchers have found evidence of its use as a polishing tool in China, dating back to 2,000 BC.

The first diamond drill was developed in 1751, and in 1871, patents for the first diamond lathe were granted. Despite years of research to create a harder substance, diamond remains the most incompressible of all materials.

Stone tools from the late prehistoric period.

Between a Rock and a Hard Metal

While diamond is super-hard, it’s rare in nature and difficult to synthesize, so it’s also super-expensive. Cost isn’t the only drawback for its industrial application. Because it reacts with iron at high temperatures, it can’t be used for cutting steel. Cubic boron nitride, another extremely hard material, can be used to cut steel and other alloys, but it requires high pressure and high temperature conditions to synthesize, making it an even more expensive material than diamond.

Today’s drill bits and cutting tools are commonly made from tool steel or cemented carbides, all significantly softer than diamond, with a tendency to wear out quickly.

Advancements in machinery and engineering demand superhard, highly incompressible materials, that can withstand grueling conditions and extreme temperatures without degrading. The need for cost-efficient, wear-resistant tooling has driven the search for ultra-incompressible, superhard materials.

Common metal tools in use today.

Targeted Properties For Superhard Materials

Incompressibilty

• Important property of cutting tools
• Resistance to elastic (reversible) deformation
• Materials with high hardness are very incompressible but incompressible materials are not necessarily hard

Hardness

• One of the most important properties for cutting tools and abrasives
• Resistance to plastic (irreversible) deformation

The Next Generation

Scientists have two directions to choose from in making superhard, ultra-incompressible materials. The first, is to imitate natural diamond, by using carbon and combining it with boron or nitrogen to maintain short covalent bonds–but that involves using high-pressure and high temperatures, making it a very expensive process. The second approach is to look for metals that are already incompressible and try to make them hard. Through four generations of experiments with various formations, they’ve created materials hard enough to scratch diamond, but can still be easily cut into tools using a cost- and energy-efficient process called electric discharge machining. These superhard materials have the potential to cut deep into the market by providing a cost-effective more durable alternative to current milling, sawing and drilling tools.

Creating superhard metals to meet industrial-strength challenges.