New titanium and iron diboride composite developed for cutting tools

Scientists at Tomsk Scientific Center SB RAS have determined the optimal process conditions for making a composite material based on affordable titanium and ferroboron alloy powders using self-propagating high-temperature synthesis (SHS). The resulting material promises to extend the life of heavy duty cutting tools, like those used in the woodworking industry. The research was published in the high-impact International Journal of Refractory Metals and Hard Materials .

– Titanium diboride is an in-demand industrial material, it’s hard and wear resistant, but in its pure, non-modified form it doesn’t hold up well to impact. Our goal was to find a way to make it stronger and more durable, – says Olga Lepakova, a researcher at the Laboratory of Heterogeneous Metallic Systems at Tomsk Scientific Center.

On the face of it, it may seem odd: how can something that’s hard also be fragile? To visualize this, imagine holding a large crystal vase. It may seem hard to the touch, but if you drop it, it will shatter. The same applies to titanium diboride. Figuratively speaking, the challenge was to make the vase shatterproof! According to Olga Shkoda, senior researcher at the Laboratory of Mathematical Modeling of Physicochemical Processes in Heterogeneous Systems, the solution is in adding iron to the mix.

By introducing a metallic binder, the researchers were able to significantly enhance the strength and toughness of titanium diboride, creating a composite material that resists breakage while maintaining its hardness. The process involves several steps. First, sintered material is synthesized in a reactor at a temperature of around 2000°C via SHS. This process fuses the titanium diboride with iron, which helps to hold the material together and gives it improved strength. Once sintered, the material is ground into a fine powder and then finally pressed into molds before undergoing the annealing stage. The resulting material combines the best of both worlds: the hardness of titanium diboride with the toughness of iron.

If we were to bake a cake or a pie, the right temperature and the time we set the alarm for would be crucial. The same applies here. As Olga Lepakova explained, it took a series of runs to determine the perfect temperature and timing for the annealing process. The optimal conditions for achieving the desired material properties were 1400°C for one hour.

The scientists compared two methods for incorporating iron into titanium diboride. One approach used pure titanium, iron, and expensive boron powders, while the other used more affordable ferroboron alloy powders. Not only does the latter reduce costs considerably, it also, as the optical and electron microscopy analyses show, improves the microstructure of the material, resulting in improved mechanical properties such as greater strength, hardness, and wear resistance.

The new composite material has already been put to the real-world test. 360 mm circular saw blades equipped with tips made of a tungsten-free hard alloy based on titanium diboride and iron were successfully tested at a fiberboard manufacturing plant. These tips proved to increase the tool’s wear resistance by more than 20 % compared to traditional, expensive tips made from tungsten carbide and cobalt (VK15), providing a significant boost to tool life. The titanium diboride-based blades were able to operate for 14 hours without needing sharpening, compared to 12 hours for the tungsten carbide blades.

The new titanium diboride and iron composites could also be used in a range of industrial applications, including abrasive pastes, magnetic abrasive powders, sintered hard alloys for tools and construction, and wear-resistant coatings. Looking ahead, the researchers plan to explore more possibilities by synthesizing materials based on titanium borides with the addition of nickel and other metals.