Carbides, Mechanical Engineering


Carbides of titanium, zirconium, boron and silicon are significant refractory materials. Though, the carbides have extremely high melting points so they lack oxidation resistance.

Carborundum, a well identified abrasive material is silicon carbide or SiC. Such material has extremely high hardness, high thermal conductivity, extremely high refractoriness, and has semi-conducting nature. Silicon Carbide's electrical conductivity is low at low temperature but raises by order of magnitude at high temperatures. When 60 percent sand and 40 percent coke along with some saw salt and dust and heated in an electric arc furnace at a temperature of about 1425oC, the resulting product is Silicon Carbide. The SiC removed from the furnace is a mass of interlocking crystals. Several shapes may be acquired when SiC is ground, mixed along with binding agent, fixed and shaped. The most widely and oldest utilized is the clay bonded material. Within this material refractory clay is added as the bonding agent. The bond in such combination softens at 1200-1500oC. Silicon and silicon nitride, are other binding materials. Silicon bonded Silicon Carbide also has its employ limited to a temperature below 1500oC due to loss in bond strength. Silicon nitride bonded SiC, though, retains its strength at great higher temperature and shows also much better shock resistance. Though a monoxide, a layer of SiO2 is formed on SiC. Such oxide layer protects SiC from more oxidation. Adding of 0.5 to 1% B throughout sintering helps uniform structure and imparts stability. SiC fibres have been utilized as reinforcement in metal and ceramics. Reaction bonded SiC is made via two distinct processes. In one procedure a compact of SiC, an organic and carbon binder is infiltrated via liquid Si that bonds the particles by formation of additional SiC. The free Si might be leached out along with acid to leave an open porous refractory. Thin walled coating or components of SiC is produced via decomposition of gas mixture containing both Silicon and C on a heated substrate. The fuel elements of high temperature gas cooled elements are produced via this process. Recently slip casting has also been utilized for silicon carbides. It has resulted in products of superior refractoriness, density, abrasion resistance and high strength, and good chemical resistance also. Silicon carbide refractories are characterized via low thermal expansion and high thermal conductivity. They tend to oxidize gradually in air at a temperature range of 900-1300oC.

Posted Date: 2/27/2013 1:50:33 AM | Location : United States

Related Discussions:- Carbides, Assignment Help, Ask Question on Carbides, Get Answer, Expert's Help, Carbides Discussions

Write discussion on Carbides
Your posts are moderated
Related Questions
Theore m of perpendicular axis It states that if I X X and I Y Y   be the M.I. of plane section about the two mutually perpendicular axes meeting at a point. Th

Design varies with scale of operation The design of a fermenter varies with scale of operation from lab (1-20L), to pilot (up to 5000L) to production (to >200,000L) scales. Th

Gun fires - projectile motion: A gun fires a projectile along with a muzzle velocity of 300 m/sec as illustrated in Figure. Find its angle of inclination so that it strikes a

What are relevant design considerations? The relevant design considerations may be summarized as follows: a. Main reinforcement (uniformly distributed) is placed in a longit

Stroke: The nominal distance through which a working piston moves between two successive reversals of its direction of motion is called the stroke and is designated by the letter

Frictionless pulley: The frictionless pulley A is being supported by two bars AB and AC which are hinged at points B and C to a vertical wall. The flexible cable D

Can you Differentiate between : Dynamometer and Brakes. Absorption Dynamometer and Transmission Dynamometer.

Determine the value of the maximum shear stress: A circular beam of 100 mm diameter is subjected to a shear force of 5 kN. Determine the value of the maximum shear stress & al

Method of section: Define the method of section? How can you solve the problems with the help of method of section? Sol.: This method is powerful method for determining

Friction: you have learnt laws of friction and problems involving dry friction. The relative sliding motion of one body on another body is resisted by forces called as frictio