Engineering breakthrough: Scientists 3D-print one of the world's hardest metals

The breakthrough could eventually help make complex industrial components with less material waste, while avoiding damage to their internal structure.

In Short

• Japanese scientists 3D print tungsten carbide-cobalt without losing hardness
• Hot-wire laser irradiation softens rather than melts the metal
• Nickel alloy layer prevents defects and maintains material quality

Scientists in Japan have found a new way to 3D print one of the hardest materials used in industry, and that too, without destroying the very properties that make it so valuable.

Researchers at Hiroshima University have successfully produced tungsten carbide-cobalt (WC-Co), cemented carbide using a laser-based 3D-printing technique.

The resulting material had a hardness of more than 1,400 HV, a measure of how strongly a material resists being scratched or indented.

That does not make it the world's strongest metal. But it does put the material among the hardest engineering materials commonly used in industry.

WHY IS THIS MATERIAL SO HARD?

WC-Co is widely used for cutting tools, drills, machining equipment and construction tools because it can withstand intense wear and repeated use.

It combines tungsten carbide, which provides the extreme hardness, with cobalt, which acts as a metallic binder holding the carbide particles together.

The problem is that making these components is difficult and expensive.

Conventional manufacturing generally involves compressing tungsten carbide and cobalt powders and heating them through a process called sintering. Because tungsten and cobalt are costly, wasting material is a major drawback.

This is where 3D printing could make a difference.

Instead of shaping a large amount of material and removing what is not needed, additive manufacturing builds an object by depositing material where it is required.

THE TRICK TO MAKING THE METAL PERFECTLY

The researchers used a process called hot-wire laser irradiation, which combines a laser with preheated filler wire.

The key breakthrough was to soften the material rather than fully melt it.

Completely melting tungsten carbide can change its internal structure and damage the properties that give it its exceptional hardness.

The team tested different ways of directing the laser.

One approach produced defects because some tungsten carbide decomposed. Another suppressed that problem but allowed iron from the base material to enter the structure, reducing its hardness.

Researchers overcame this by adding a middle layer made from a nickel-based alloy and carefully controlling the temperature.

The final material exceeded 1,400 HV without tungsten carbide decomposition or major defects.

The achievement could eventually make it easier to manufacture complex carbide components while using less expensive raw material.

- Ends