Silicon Nitride in Metal Working and Cutting Tools

Silicon nitride saw its first major industrial application in abrasive and cutting tools. Due to its hardness, thermal stability, and wear resistance, silicon nitride was found to work well with cutting tools, especially during high-speed machining of cast iron1. The superior material properties of Si3N4 can cut cast iron and hard steel as well as nickel-based alloys with surface speeds up to 25 times faster than conventional machining materials such as tungsten carbide. The benefits of using silicon nitride inserts range from doubling cutting speed, extending tool service life from one part to six parts per edge, and reducing the average cost of inserts by 50 percent as compared to conventional tungsten carbide tools.

Hard and Chemically Resistant

Ceramics based on silicon nitride offer increased resistance to abrasion and thermal shock and have high fracture toughness. These ceramic tools have a needle-like structure that is embedded in a temperature-resistant grain-boundary. These structures enhance crack deflection, crack bridging, and pull-out effects, and lead to superior fracture toughness.

When used with powerful machine tools, silicon nitrides enable high cutting speeds (more than 800 in./min.) and feeds (0.2 to 0.3 in./min.) for rough boring cast iron2.

Advantages of Silicon Nitride

High mechanical strength
Silicon nitride maintains high mechanical strength over a wide temperature range. The outstanding strength characteristics with relative low density make it easy to handle compared to conventional materials.

Chemical stability
Silicon nitride is inert against molten metal even at high temperature. It ensures longer work life with low maintenance.

Superior thermal shock resistance
Silicon nitride has exceptional thermal shock resistance, making it ideal for applications with high dynamic stresses, high operating temperature, and demanding reliability requirements3.

References

1. https://www.sciencedirect.com/science/article/pii/0261306986900531

2. https://www.nextgentooling.com/technical/five-types-of-cermamic-cutting-tools

3. https://www.elsevier.com/books/ceramic-cutting-tools/whitney/978-0-8155-1355-1

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