Gas Pressure Sintered Silicon Nitride
Gas Pressure Sintered Silicon Nitride, GPSN Ceramic
Gas Pressure Sintered Silicon Nitride
Gas Pressure Sintered silicon nitride ceramics is the most common method for producing high-strength and complex geometric silicon nitride parts. Therefore, when we usually refer to silicon nitride ceramics, they are assumed to be gas-pressure silicon nitride ceramics without any remarks.
To greatly improve the high-temperature performance of the material, scientists replaced MgO with Y2O3 as a sintering aid, but the effect of Y2O3 as an aid in promoting liquid phase sintering is not as good as MgO, so the sintering temperature needs to be further increased. However, the increase in temperature will make the high-temperature decomposition of silicon nitride more significant, and it is necessary to further improve the process to inhibit the high-temperature decomposition of silicon nitride and promote the densification of the sintered body, so gas pressure sintering of silicon nitride was developed. The process is: usually use silicon nitride powder that has been fully mixed with a sintering aid to promote liquid phase sintering (usually yttrium oxide, magnesium oxide, and/or aluminum oxide), and mix part of the binder to improve the mechanical strength of the green ceramic body. Silicon nitride powder is pressed into the desired shape, then green body processing is performed, and finally, the pressed green body is placed in a sintering furnace filled with nitrogen and sintered at high temperature to form.
The common conditions of gas pressure sintering are sintering temperature controlled at about 2000℃ under a pressure of 1~10MPa, which is slightly higher than other sintering methods. When adding fewer sintering aids, can also promote Si3N4 grain growth. The final sample prepared is a long columnar grain ceramic with high density and strength. Silicon nitride prepared by gas pressure sintering has high strength, toughness, and wear resistance. At the same time, products of various complex shapes can be formed and sintered, so it has a wider range of uses than silicon nitride prepared by other processes.
Advantages of Gas Pressure Sintered Silicon Nitride
Si3N4 Ceramic Rods
High density, high strength, good wear resistance, can manufacture products with complex shapes, suitable for large-scale production
Disadvantages of GPSN
Process conditions are relatively difficult to control
Applications
In addition to the thermocouple protection tubes, melting metal crucibles, rocket nozzles, ceramic tools, bearing balls, sealing rings, and roller rings in the metallurgical industry, and vessels for carrying molten metal, Gas pressure sintered silicon nitride ceramics are widely used in ceramic turbine engine components, such as vortex chamber silver blocks, tappets, rocker arm silver blocks, glow plugs, turbocharger rotors and valves in the engine; in addition, it is also widely used in high temperature and high-stress components in gas turbines, such as stator blades, moving blades, volutes, etc.
