As our developer Dominik Zug highlighted in his previous post, our goal is to develop boron nitride ceramics that are not currently available on the market or that meet specific requirements which cannot be met—or can only be met inadequately—by conventional materials. With our HeBoSint® SL-N 300, a composite ceramic consisting of boron nitride and a silicon-aluminum oxynitride, we have succeeded in developing a material with exceptional properties.
What makes the HeBoSint® SL-N 300 so special?
A strong material in every respect, but what does that actually mean? If we take a look at the spider web diagram, it quickly becomes clear where the strengths of our BN-SiAlON lie.
high wear resistance
high bending strength
good thermal shock resistance
low thermal expansion
excellent gas tightness,
excellent separation performance
and excellent electrical insulation properties.
Last but not least, this combination of materials ensures excellent chemical resistance. All these properties combine to create a robust product.
Mechanical properties
Flexural strength [MPa]: Flexural strength represents the maximum value a component can withstand under compression or tension before it breaks under bending stress. It is one of the most important properties for estimating the strength and sizing of components. Factors influencing the flexural strength of a component include microstructural homogeneity, grain size, grain morphology, and surface finish. In general, technical ceramics are characterized by very high flexural strengths at high temperatures. This makes them particularly well-suited for use in high-temperature processes, among other applications. Our HeBoSint® SL-N 300 typically exhibits a value of approximately 120 MPa perpendicular to the pressing direction and approximately 95 MPa parallel to the pressing direction. This allows for a wide variety of geometries and even thin wall thicknesses, providing a high degree of design freedom when configuring the component.
Modulus of elasticity [GPa]: The modulus of elasticity is another parameter used to assess strength; simply put, it indicates a material’s elasticity—that is, how well it resists deformation when a force is applied.
Here, the values are 45 GPa perpendicular to the pressing direction and 30 GPa parallel to the pressing direction. By comparison, a pure boron nitride ceramic has values of approximately 23 GPa and 20 GPa, respectively.
Compressive strength [MPa]: This parameter indicates how well a material withstands compressive forces applied from one or more sides. The compressive strength of technical ceramics is often 5 to 10 times higher than their flexural strength, which is why compressive loading is preferred when planning the application of the material.
The compressive strength values for HeBoSint® SL-N 300 are 270 MPa perpendicular to the pressing direction and 315 MPa parallel to the pressing direction.
Comparison with other ceramic materials on the market
As mentioned earlier, engineering ceramics are typically characterized by high mechanical properties. In this context, the values mentioned above for the flexural strength, modulus of elasticity, and compressive strength of our material are considered moderate when compared to other ceramics. Compared to oxide ceramics, such as alumina and zirconia, the advantages of HeBoSint® SL-N 300 lie primarily in its thermal shock resistance and its ability to separate from molten metals. While, for example, alumina withstands temperatures of up to 1600 °C, HeBoSint® SL-N 300 can be used at temperatures of up to 1800 °C. Likewise, the thermal expansion of 2.5 to 4.6·10⁻⁶ K⁻¹ is significantly lower than that of aluminum oxide (approx. 7·10⁻⁶ K⁻¹) or zirconia (approx. 10·10⁻⁶ K⁻¹), which contributes significantly to the aforementioned high thermal shock resistance. In direct comparison to carbide materials, such as silicon carbide, which exhibits a similarly low thermal expansion (approx. 3.5 × 10⁻⁶ K⁻¹) and also high temperature resistance, the specific electrical resistivity stands out in addition to the higher reactivity toward molten steel. For silicon carbide, this is approximately 105 Ωcm and is thus significantly lower than that of HeBoSint® SL-N 300, which has a value of approximately 1015 Ωcm.
Customer Experiences and Outlook
Early customer feedback indicates that we can offer genuine added value with the development of this ceramic. Over the next few weeks, we will delve into its other properties to ultimately provide as comprehensive an overview as possible of how to interpret each property and how they relate to one another. After all, it is only through the interplay of these various parameters that it becomes possible to select the right material.