Hiroshima University researchers use AM to produce cemented carbides
Researchers from Hiroshima University, Japan, have published a study titled ‘Effect of the hot-wire laser irradiation method and a Ni-based alloy middle layer on mechanical properties and microstructure in Additive Manufacturing of WC–Co cemented carbide’ in the International Journal of Refractory Metals and Hard Materials. The reported work utilises Additive Manufacturing and hot-wire laser irradiation to produce cemented carbides without sacrificing hardness and durability, while also reducing material waste and overall cost.
Tungsten carbide–cobalt (WC–Co) is prized for its hardness, but that same property makes it difficult to shape. Conventional processing is material-intensive and costly, the authors stated.
The study focuses on the use of AM, specifically hot-wire laser irradiation, along with two fabrication methods for the experiment. Hot-wire laser irradiation is a technique in which a laser beam and a preheated filler wire are combined to increase the deposition rate and efficiency of the process.
One fabrication method used in this study involves direct irradiation on top of the cemented carbide rod, with the rod leading the direction of fabrication. In the second method, the laser leads the process and irradiates the region between the bottom of the cemented carbide rod and the base material (iron). In both methods, the metals are softened instead of completely melted to form the cemented carbide.
Corresponding author Keita Marumoto, assistant professor at Hiroshima University’s Graduate School of Advanced Science and Engineering, shared, “Cemented carbides are extremely hard materials used for cutting tool edges and similar applications, but they are made from very expensive raw materials such as tungsten and cobalt, making reduction of material usage highly desirable. By using additive manufacturing, cemented carbide can be deposited only where it is needed, thereby reducing material consumption.”
The results reportedly demonstrated that this method is effective in maintaining the hardness and mechanical integrity of conventionally manufactured WC-Co cemented carbides, achieving a base material with hardness of over 1400 HV (a unit representing resistance to penetration), without introducing any defects or decomposition. Materials at this hardness level reportedly rank among the toughest used in industry. The researchers claimed that it does appear possible to produce the cemented carbide molds without defects, which is the main goal of the study, though some results varied.
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For example, the rod-leading method appears to lead to the decomposition of WC on the upper part of the build, leading to defects in the final product. The laser leading method also had issues maintaining the hardness necessary for success. The researchers found that adding a nickel-based middle layer, while maintaining the temperature above cobalt’s melting point but below that associated with grain growth, enabled the production of AM cemented carbide without a significant loss of hardness.
The researchers now aim to address cracking and fabricate more complex shapes.
“The approach of forming metal materials by softening them rather than fully melting them is novel, and it has the potential to be applied not only to cemented carbides, which were the focus of this study, but also to other materials,” said Marumoto.
The team intends for future work to focus on cutting-tool fabrication, the use of other materials, and further durability improvements.
Keita Marumoto and Motomichi Yamamoto of the Graduate School of Advanced Science and Engineering at Hiroshima University and Takashi Abe, Keigo Nagamori, Hiroshi Ichikawa and Akio Nishiyama of the Mitsubishi Materials Hardmetal Corporation contributed to this research.
The full study is available here.
