Karbid křemíku - vysoká pevnost a odolnost

Karbid křemíku je vysoce výkonný materiál, který je odolný vůči chemické korozi a teplotám dosahujícím 1 900 °C. Karbid křemíku se vyrábí smícháním jemného prášku a-SiC s neoxidovými spékacími přísadami a zhutňuje se pomocí běžných keramických tvářecích procesů, jako je izostatické lisování, tlakové lití nebo vstřikování, a obvykle se vyrábí ve velkých objemech pro použití jako keramické tvářecí nástroje.

Reaction sintering is one of the most appealing manufacturing processes for silicon carbide ceramic due to its density, low processing temperature and good shape capability. Unfortunately, reaction sintered silicon carbide has lower bending strength compared to standard sintered sic.

Vysoká pevnost

Silicon carbide offers superior strength, abrasion resistance, chemical stability and temperature resistance – ideal characteristics for industrial applications that demand long-term durability.

Pressureless sintering is the go-to production technique. This technique utilizes fine SiC powders mixed with sintering additives and produces dense ceramic structures at a relatively low processing temperature, offering several benefits such as lower costs and good shape ability; however, particle size limitations and additive content must also be taken into consideration.

Other production techniques, including reaction bonded and direct sintered SiC, produce denser structures at higher processing temperatures that alter its microstructure. Reaction bonded SiC is more suitable for applications not demanding such high properties as it features coarse grain structure with lower costs compared to pressureless sintered. Saint-Gobain Hexoloy SA SiC provides excellent wear resistance, flexural strength, thermal shock resistance, etc.

High Hardness

Silicon carbide is one of the hardest ceramics on Earth, boasting an astounding Mohs hardness of 9.5. This provides exceptional abrasion resistance and wearability even under harsh environmental conditions, along with exceptional high temperature resistance that makes it suitable for gas turbine blades and nuclear reactors.

Reaction-bonded and direct sintered silicon carbide production techniques exist. Reaction bonded SiC is produced by infiltrating molten silicon into porous carbon or graphite preforms with the aim of reacting with carbon to form b-SiC which then bonds with existing a-SiC particles for full density without shape shrinkage. Direct sintered SiC production occurs via thermal treatments combining melting liquid silicon and graphite particles.

Direct sintered silicon carbide is produced by mixing pure silica powder with oxide-free sintering aids in an inert atmosphere and pressing them using conventional ceramic forming techniques, before sintering at high temperature to form dense ceramic with excellent mechanical properties.

Vysoká odolnost proti korozi

Silicon carbide is a dense material with excellent resistance to corrosion, oxidation and wear. Furthermore, its thermal impact and tribological properties make it highly sought-after by manufacturers.

SiC’s corrosion resistance is determined by its composition, additives and crystal orientation within a sintered ceramic. Reaction bonded silicon carbide (RSiC) commercially available has an exceptional room temperature bending strength exceeding 300 MPa with low crack strength sensitivity.

Pressureless sintered silicon carbide can be made using ultrafine SiC powder blended with non-oxide sintering aids, compacting it using traditional ceramic forming methods such as isostatic pressing and die pressing, then sintering at high temperatures in an inert atmosphere at temperatures exceeding 600 oF (304oC). Usually this produces an average grain size of 1.5 mm with an excellent relative density greater than 95% that can then easily be machined using precision diamond-coated tools into tolerances and shapes – an economical method of producing precise wear-resistance parts for demanding applications that will deliver reliability in production time and cost efficiency!

Low Density

Silicon carbide ceramic is denser than other ceramics and is therefore capable of withstanding extreme impacts and stresses that would fracture other materials, thanks to its dense structure, made up of compact crystalline structures that offer exceptional resistance.

Sintered silicon carbide boasts low electrical resistivity, making it an ideal material for pump seals that must operate in challenging environments. Furthermore, its ceramic composition provides both abrasion resistance and corrosion protection.

Denser ceramic can be produced using various techniques, including reaction sintering where liquid silicon or silicon alloy is infiltrated into a porous green body to react and form silicon carbide, which then reacts with existing a-SiC particles and forms silicon carbide. Pressureless sintering also used ultra-pure submicron a-SiC powder mixed with non-oxide binders to form paste; then sintered at high temperatures to produce denser ceramic composition.