Nitride Bonded Silicon Carbide

Nitride-bonded silicon carbide (NbSC) is a high-temperature ceramic material widely used across a range of applications. To produce it, silicon powder and gaseous nitrogen are mixed at elevated temperatures with the aid of magnesium as a sintering aid.

Nitride-bonded silicon carbide was discovered to have much higher wear resistance than steel in light soil with loose grains of sand, and over six times greater in heavy soil; however, its wear pattern varied depending on the type of soil in which it was placed.

High Temperature Strength

Nitride-bonded silicon carbide offers excellent thermal shock resistance and can withstand sudden temperature shifts without cracking or fracture. Furthermore, its surface resists chemical attacks and oxidation for maximum protection against degradation.

NB SiC’s strength lies in its production process: nitridation. This involves casting/pressing/injection moulding a mixture of silicon carbide grains and metallic silicon powder into an injection mold and heating in a nitrogen rich atmosphere until all metallic silicon powder has been transformed into ceramic-rich phases that bond silicon carbide grains together into one solid mass, creating an impenetrable ceramic phase and shatter-proof and shrinkage-free product, perfect for producing bricks that will be used in furnaces and kilns.

Nitride-bonded silicon carbide outshines reaction infiltrated silicon carbide by far. Reaction infiltrated material usually has pores of 5- 15% and should only be used in low stress applications without being directly attacked from nonferrous metals or molten slags. Nitride bonded silicon carbide also outperforms hot-pressed and hot isostatic pressed varieties which both feature higher porosities, restricting application in small geometries only.

Extreme Hardness

Nitride-bonded silicon carbide (NBSC) is an extremely tough material with exceptional wear resistance, boasting a hardness of 1080, much higher than steel, which enables near net shapes that replicate metal components to be machined from it. As such, NBSC makes for an ideal replacement of alloys or other refractory materials in severe service conditions; and can also serve as an abrasion resistance application such as cyclone liners in mineral plants and coal power stations as well as corrosion-resistant applications in chemical plants.

Nitride-bonded silicon carbide displays strong impact wear resistance in light soil conditions, but its wear resistance suffers in heavier ones due to loose abrasive grains of sand attacking its surface. This type of wear is often described by scratching and furrowing rather than aggressive erosion like that seen with materials like XAR 600 steels or F-61 padding welds.

Sintered silicon carbide offers excellent thermal shock and creep resistance, making it the ideal material for high temperature uses between 1300-1650oC. Furthermore, its unique mechanical strength, low coefficient of linear expansion, good chemical stability and easy working microstructure make this material extremely user friendly. At IPS Ceramics we can supply sintered silicon carbide batts, setsters tubes or beams to meet all your kiln furniture requirements.

Good Mechanical Strength

Nitride-bonded silicon carbide’s high mechanical strength makes it an excellent material for abrasion resistance. In light soil conditions, its higher resistance than steels such as boron steel or F-61 padding weld makes it even more resilient against wear than their steel counterparts; its precise path of wear ultimately depends on how abrasive particles interact with friction surfaces – loose grains of sand moving freely around may scratch these surfaces while hard-wearing particles may chip them.

Nitride-bonded silicon carbide is produced by nitriding a moulded body of SiC granulate and metallic silicon powder in an atmosphere of nitrogen. During this process, metallic silicon transforms to silicon nitride that bonds tightly to SiC grains to form a dense structure.

The resultant material is not only resistant to chemical attack and corrosion at temperatures up to 1600oC, but also offers excellent mechanical strength – qualities which make NB SiC ideal for applications such as kiln furniture, wafer tray supports and paddles or any other high temperature low pressure applications. IPS Ceramics provides both open porous and fully dense forms of this material.

Chemically Inert

Nitride-bonded silicon carbide is not vulnerable to chemical attack, making it suitable for applications involving aggressive chemicals. Furthermore, it provides excellent thermal shock resistance.

Refractory ceramic is an ideal material to use when it comes to road construction projects where heavy trucks are in use, thanks to its excellent wear properties in abrasive soil mass and ability to withstanding vehicle pressure at high temperatures. As such, it makes an excellent choice for pavement and road paving applications where heavy trucks may be utilized.

How nitride-bonded silicon carbide wears away depends on the nature and grain size distribution of an abrasive soil mass. Light soil typically results in loose sand grains moving freely across its surface scratching friction surfaces; with heavier soil masses, abrasive effects are reduced and micro-cutting takes place, leading to the removal of any soft layers (Figure 1).

Reaction bonded silicon carbide (RB SiC) is created by injecting molten silicon into porous carbon material packed into the desired part, leading to its reaction and formation as SiC. RB SiC is an extremely hard material with excellent mechanical strength, capable of being produced into various shapes and sizes for use as mechanical seals, bearings or flow control chokes.

Corrosion Resistance

Nitride-bonded silicon carbide (NiC) is an extremely strong ceramic material composed of SiC particles fused together via nitridation. Nitride bonded SiC is ideal for applications requiring high load bearing capacities and temperature resistance, such as heavy machinery.

NBSiC is resistant to corrosion caused by acids, molten salts and halogens. Furthermore, this material demonstrates good slag resistance and high thermal shock resistance; furthermore it can withstand temperatures up to 1650 degrees Celsius while maintaining excellent mechanical properties.

Corrosion of NBSiC is a multistep process, affected by various species, impurities, sintering aids, grain boundary phases, porosity and surface morphologies. Sacrificiarised oxide layers on substrates have been known to promote parabolic reaction kinetics that reduce oxygen diffusion rate.

NBSiC wear resistance was found to depend on the type of soil mass it was exposed to. Light soil showed its best wear characteristics compared to steels and padding weld, while medium and heavy soil displayed its least wear attributed to slag penetration that causes soft particles from NBSiC to chip off over time.

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