Niobium carbide
Encyclopedia
Niobium carbide is an extremely hard refractory
ceramic
material, commercially used in tool bit
s for cutting tools. It is usually processed by sintering
and is a frequent additive in cemented
carbides. It has the appearance of a brown-gray metallic powder with purple lustre. It is highly corrosion
resistant.
Niobium carbide is a frequent intentional product in microalloyed
steels due to its extremely low solubility product in austenite
, the lowest of all the refractory metal carbides. This means that micrometre-sized precipitates of NbC are virtually insoluble in steels at all processing temperatures and their location at grain boundaries helps prevent excessive grain growth in these steels. This is of enormous benefit, and the cornerstone of microalloyed steels, because it is their uniform, very fine grain size that ensures both toughness and strength.
The only commonly occurring compound with a lower solubility and hence, greater potential for restricting the grain growth of steels is titanium nitride
.
Its CAS number is 12069-94-2.
Depending on grain size, niobium carbide may burn at 200-800 °C in air.
A layer of niobium carbide can be created by chemical vapor deposition
.
Zirconium carbide
and niobium carbide can be used as refractory coatings in nuclear reactor
s.
Refraction (metallurgy)
In metallurgy, refraction is a property of metals that indicates their ability to withstand heat. Metals with a high degree of refraction are referred to as refractory. These metals derive their high melting points from their strong intermolecular forces...
ceramic
Ceramic
A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
material, commercially used in tool bit
Tool bit
The term tool bit generally refers to a non-rotary cutting tool used in metal lathes, shapers, and planers. Such cutters are also often referred to by the set-phrase name of single-point cutting tool. The cutting edge is ground to suit a particular machining operation and may be resharpened or...
s for cutting tools. It is usually processed by sintering
Sintering
Sintering is a method used to create objects from powders. It is based on atomic diffusion. Diffusion occurs in any material above absolute zero, but it occurs much faster at higher temperatures. In most sintering processes, the powdered material is held in a mold and then heated to a temperature...
and is a frequent additive in cemented
Cementation
Cementation may refer to:*Cementation , the process of deposition of dissolved mineral components in the interstices of sediments*Cementation , a small deposit of calcium, similar to a cyst...
carbides. It has the appearance of a brown-gray metallic powder with purple lustre. It is highly corrosion
Corrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
resistant.
Niobium carbide is a frequent intentional product in microalloyed
HSLA steel
High-strength low-alloy steel is a type of alloy steel that provides better mechanical properties or greater resistance to corrosion than carbon steel. HSLA steels vary from other steels in that they are not made to meet a specific chemical composition but rather to specific mechanical properties...
steels due to its extremely low solubility product in austenite
Austenite
Austenite, also known as gamma phase iron, is a metallic non-magnetic allotrope of iron or a solid solution of iron, with an alloying element. In plain-carbon steel, austenite exists above the critical eutectoid temperature of ; other alloys of steel have different eutectoid temperatures...
, the lowest of all the refractory metal carbides. This means that micrometre-sized precipitates of NbC are virtually insoluble in steels at all processing temperatures and their location at grain boundaries helps prevent excessive grain growth in these steels. This is of enormous benefit, and the cornerstone of microalloyed steels, because it is their uniform, very fine grain size that ensures both toughness and strength.
The only commonly occurring compound with a lower solubility and hence, greater potential for restricting the grain growth of steels is titanium nitride
Titanium nitride
Titanium nitride is an extremely hard ceramic material, often used as a coating on titanium alloys, steel, carbide, and aluminium components to improve the substrate's surface properties....
.
Its CAS number is 12069-94-2.
Depending on grain size, niobium carbide may burn at 200-800 °C in air.
A layer of niobium carbide can be created by chemical vapor deposition
Chemical vapor deposition
Chemical vapor deposition is a chemical process used to produce high-purity, high-performance solid materials. The process is often used in the semiconductor industry to produce thin films. In a typical CVD process, the wafer is exposed to one or more volatile precursors, which react and/or...
.
Zirconium carbide
Zirconium carbide
Zirconium carbide is an extremely hard refractory ceramic material, commercially used in tool bits for cutting tools. It is usually processed by sintering. It has the appearance of a gray metallic powder with cubic crystal structure...
and niobium carbide can be used as refractory coatings in nuclear reactor
Nuclear reactor
A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...
s.