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| A tungsten carbide ring |
For decades, the manufacturing industry has relied on a super-material known as tungsten carbide–cobalt (WC–Co) to build the tools that build our world. Prized for its incredible hardness—often rivaling that of sapphire and diamond—this cemented carbide is the go-to choice for drill bits, cutting tools, and wear-resistant parts.
But there has always been a catch: shaping it is a nightmare.
Traditional methods of forming WC–Co, such as powder metallurgy, are notoriously expensive and wasteful. Machining this ultra-hard material often requires diamond abrasives, and creating complex geometries can be a logistical and financial challenge. However, a breakthrough from researchers at Hiroshima University is poised to change that, proving that you can teach an old material new tricks.
In a study published in the International Journal of Refractory Metals and Hard Materials, the Japanese research team has successfully 3D-printed tungsten carbide-cobalt without sacrificing the legendary toughness that makes it so valuable.
The "Hot-Wire" Solution to a Hard Problem
The core issue with 3D printing metals as hard as WC–Co is that traditional additive manufacturing methods, which rely on fully melting the feedstock, often result in cracking, porosity, or a loss of the material's desired properties.
The Hiroshima University team circumvented this by utilizing a technique known as hot-wire laser irradiation. Unlike standard laser powder bed fusion that melts material completely, this method takes a different approach. It combines a high-powered laser beam with a preheated filler wire. Instead of obliterating the structure of the metals, the heat merely softens them enough to create a strong, dense bond.
"Cemented carbides are extremely hard materials... but they are made from very expensive raw materials such as tungsten and cobalt, making reduction of material usage highly desirable," explained Assistant Professor Keita Marumoto, the corresponding author of the paper, in a recent statement. "By using additive manufacturing, cemented carbide can be deposited only where it is needed, thereby reducing material consumption."
This "directed energy deposition" approach means manufacturers could soon print parts exactly where they are needed, with minimal waste—a massive advantage given the high cost of raw tungsten.
Overcoming the Heat
The path to success wasn't without its hurdles. The team initially experimented with two fabrication orientations: "rod-leading" and "laser-leading." However, these early attempts were plagued by defects and unwanted material decomposition. The intense heat required to fuse the materials was causing the cobalt binder to behave unpredictably, leading to grain growth that weakened the final product.
As detailed in a report on the breakthrough from TechXplore, the researchers pivoted their strategy. They discovered that by introducing a nickel alloy-based middle layer and strictly controlling the temperature to stay above cobalt’s melting point but below the threshold where grain growth occurs, they could achieve a pristine result.
The final product was a defect-free material boasting a hardness of over 1,400 HV (Vickers Pyramid Number)—a figure that puts it on par with conventionally manufactured carbides. This proves that the additive method does not compromise the structural integrity that engineers depend on.
The Future of Cutting Tools
The implications of this research extend far beyond the lab. For industries reliant on cutting, drilling, and wear-resistant components, this could signal a major shift in supply chains.
Currently, creating a custom carbide tool often requires specialized molds or extensive machining time. With this new 3D-printing technique, manufacturers could theoretically print custom tools on-demand, reducing lead times from weeks to hours.
The researchers are now focused on refining the process to prevent micro-cracking and to allow for the fabrication of even more complex shapes. If they succeed, we could see a future where the hardest materials on earth are as easy to print as plastic, revolutionizing everything from aerospace engineering to medical device manufacturing.