Hiroshima University 3D Prints Tungsten Carbide-Cobalt With Less Waste

The Material Problem

Tungsten carbide-cobalt, or WC-Co, is one of the hardest materials used in industry. It shows up in cutting tools, drill bits, mining equipment, and anything that grinds against other materials for a living. The problem is that making it is expensive and wasteful. Conventional powder metallurgy compresses fine tungsten and cobalt powders under high pressure, then sinters them at high temperatures. The process works, but it uses more raw material than ends up in the finished part, and tungsten and cobalt are not cheap.

The New Approach

Researchers at Hiroshima University and Mitsubishi Materials Hardmetal Corp. tested a hot-wire laser irradiation process that deposits WC-Co only where it is needed. A preheated filler wire feeds into a laser beam, softening the material without fully melting it. That distinction matters. Fully melting tungsten carbide can change its internal structure and reduce the hardness that makes it useful.

The team ran two experimental setups. In the first, the laser hit the top of a cemented carbide rod while material built ahead of the rod. In the second, the laser led the process and heated the area between the rod and the base material. Both arrangements avoided full melting, depositing softened carbide instead.

Results

The printed structures reached hardness levels above 1400 HV on the Vickers scale. That puts the material among the toughest commonly used in industrial settings. The researchers had to clear two major hurdles. First, the rod-leading arrangement caused some tungsten carbide to decompose near the top of the build, creating defects. Second, the laser-leading arrangement initially failed to hold the target hardness.

The team solved both problems by adding a nickel alloy intermediate layer and controlling the temperature carefully. The heat stayed above cobalt's melting point but below the temperature where grain growth occurs. Grain growth enlarges the microscopic crystals inside the material, which softens it and ruins wear resistance. With those controls in place, the process produced defect-free carbide without sacrificing hardness.

What Comes Next

The researchers want to reduce cracking, produce practical cutting tools, and test the method with other advanced materials. If the technique scales, it could let manufacturers place expensive carbide only where wear actually happens. That would cut material costs and waste while keeping the extreme hardness required for industrial tools.

The study was published in the International Journal of Refractory Metals and Hard Materials. The lead author is Keita Marumoto, assistant professor at Hiroshima University's Graduate School of Advanced Science and Engineering.