As already emphasised in the last article by our developer Dominik Zug, our aim is to develop boron nitride ceramics that are not available on the market in this form or fulfil special requirements that cannot be met or can only be met inadequately with conventional materials. With our HeBoSint® SL-N 300, a composite ceramic consisting of boron nitride and a silicon-aluminium oxynitride, we have succeeded in developing a material with a strong character.
What makes HeBoSint® SL-N 300 so special?
A strong character in every respect, but what does this mean in concrete terms? If we take a look at the spider web diagram, it quickly becomes clear where the strengths of our BN-SiAlON are:
high wear resistance
high flexural strength
good thermal shock behaviour
low thermal expansion
outstanding gas tightness
very good separation behaviour
and excellent electrical insulation capacity
Last but not least, this combination of materials ensures very good chemical resistance. All these properties form a strong character.
The mechanical properties
Flexural strength [MPa]: The flexural strength represents the maximum value that a component can withstand in compression or tension before it breaks under load due to bending. It is one of the most important properties for estimating the strength and dimensioning of components. Influencing variables for the factors that determine the flexural strength of the component are structural homogeneity, grain size, grain morphology and surface quality. In general, technical ceramics are characterised by very high flexural strength at high temperatures. This makes it particularly suitable for use in high-temperature processes. Our HeBoSint® SL-N 300 usually has a value of around 120 MPa perpendicular to the pressing direction and around 95 MPa parallel to the pressing direction. This enables a variety of geometries and also low wall thicknesses, which allows many degrees of freedom when designing the component.
Young's Modulus [GPa]: The young's modulus is another parameter for assessing strength and, put simply, indicates elasticity, i.e. how well a material can withstand deformation caused by the application of force.
The values here are 45 GPa perpendicular to the pressing direction and 30 GPa parallel to the pressing direction. For comparison: A pure boron nitride ceramic is approx. 23 GPa and 20 GPa respectively.
Compressive strength [MPa]: This parameter indicates how well a material can withstand a compressive force from one or more sides. The compressive strength of technical ceramics is often 5-10 times higher than the flexural strength, which is why a compressive load should be favoured when planning the use of the material.
The compressive strength values with 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 already mentioned, technical ceramics are usually characterised by high mechanical properties. The above-mentioned values for flexural strength, modulus of elasticity and compressive strength of our material can be classified as moderate compared to other ceramics. Compared to oxide ceramic materials such as aluminium oxide and zirconium oxide, the advantages of HeBoSint® SL-N 300 lie primarily in its resistance to thermal shock and its ability to separate from metallic melts. While aluminium oxide, for example, can withstand temperatures of up to 1600 °C, HeBoSint® SL-N 300 can reach temperatures of up to 1800 °C in the application. The thermal expansion of 2.5 to 4.6-10-6 K-1 is also significantly lower than that of aluminium oxide (approx. 7-10-6 K-1) or zirconium oxide (approx. 10-10-6 K-1), which leads not least to the aforementioned high thermal shock resistance. In direct comparison to carbide materials, such as silicon carbide, which has a similarly low thermal expansion (approx. 3.5-10-6 K-1) and also a high temperature resistance, the specific electrical resistance should be emphasised in addition to the higher reactivity compared to molten steel. This is around 105 Ωcm for silicon carbide and is therefore significantly lower than for HeBoSint® SL-N 300 with a value of around 1015 Ωcm.
Customer experience and outlook
Initial customer experience shows that we can offer real added value with the development of this ceramic. Over the next few weeks, we will be looking at the other properties in order to provide as comprehensive an overview as possible of how the individual properties are to be interpreted and how they relate to each other. Because only the interaction of the various parameters makes it possible to select the right material.
If you would like to find out more or would like advice, our technical sales team will be happy to help. We will be happy to advise you and work with you to find out whether our HeBoSint® SL-N 300 could be the right solution for you.
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