SIALON II VERSUS SYALON, SILICON NITRIDE AND SI3N4.

 

Sialon II is the second generation of technical ceramics for foundries and other applications. This new isostatically pressed ceramic shows a major improvement with regards to the impact fracture toughness (> 10Mpa) compared to syalon, si3n4 or Silicon Nitride. Sialon is considered to have superior properties over silicon nitride and syalon.

 

Our Sialon heater tubes, thermocouple protection tubes, riser tubes, Westofen dosing tubes, impellers, ladles, hooks, extrusion dies, cutting tools and welding pins have excellent non-wetting properties and a smooth surface.

 

With regards to Sialons, there is substitution of silicon by aluminum with corresponding atomic replacement of nitrogen by oxygen, to satisfy valency requirements.

The resulting 'solution' has superior properties to the original pure solvent, syalon, silicon nitride or Si3N4.

 

Silicon Nitride like ceramics have found extensive use in non-ferrous molten metal handling, particularly aluminum and its alloys, including metal feed tubes for aluminum die casting, burner and immersion heater tubes, injector and degassing for nonferrous metals, thermocouple protection tubes, crucibles and ladles.

 

In metal forming, it is used as a cutting tool for machining chill cast iron and as brazing and welding fixtures and pins, particularly for resistance welding.

 

Other applications include in the chemical and process industries and the oil and gas industries, due to the excellent chemical stability and corrosion resistance and wear resistance properties.
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Sialon is produced by first combining a mixture of raw materials including silicon nitride, alumina, aluminum nitride, silica and the oxide of a rare earth element such as yttrium.

 

The powder mix is fabricated in to a 'green' compact by isostatic powder compaction or slipcasting, for example. Then the shaped form is then densified, typically by pressure less sintering or hot isostatic pressing.

The sintered Sialon part may then need to by machined by diamond grinding (abrasive cutting).

Sialons are ceramic alloys based on the elements Silicon (Si), aluminium (Al), oxygen (O) and nitrogen (N). They are alloys of silicon nitride(Si3N4) and exist in three basic forms.

 

Each form is iso-structural with one of the two common forms of silicon nitride, beta and alpha and with silicon oxynitride. The relationship between that of sialon and silicon nitride is similar to that between brass and pure copper.

 

The later case, copper atoms are replaced by zinc to give a better stronger alloy than the mother metal. In the case of sialon, there is substitution of silicon by aluminium with corresponding atomic replacement of nitrogen by oxygen, to satisfy valency requirements.

 

The resulting 'solution' (sialon) has superior properties to the original pure solvent (silicon nitride) or syalon.