Equations that relate all of the flow field variables together into nonlinear partial differential equations. The NS equations are basically a reformulation of Newton's 2nd Law of Motion, F=ma. These are probably the most pivotal equations in all of theoretical fluid dynamics.
An element that is used in low alloy steels to reduce their sensitivity to variations in heat treatment and distortion or cracking upon quenching. It also improves low-temperature toughness and hardenability. Nickel is also a base metal for many casting alloys that are resistant to corrosion and high-temperature oxidation. Its melting point is 1455°C (2651°F).
(process) The electrolytic deposition of nickel to form a corrosion barrier or reclaim a worn part. Hard ceramic particles are sometimes added to form a wear-resistant composite coating.
(substance) The coating that is applied by the nickel plating process.
Hard, white cast iron containing 4% Ni and 2% Cr. Niobium (Nb) (Columbium - Cb). It lowers the transition temperature and raises the strength of low-carbon steel. Niobium increases strength at elevated temperatures, resulting in finer grain size and forming stable carbides, which lowers the hardenability of the steel.
The process of introducing nitrogen into the surface layer of a solid ferrous alloy by holding it, at a suitable temperature (below Ac1 for ferritic steels), in contact with an appropriate nitrogenous composition. Quenching is not required to produce a hard case. See aerated bath nitriding, bright nitriding and liquid nitriding.
Any of several processes in which both nitrogen and carbon are absorbed into the surface layers of a ferrous material at temperatures below the lower critical temperature and, by diffusion, create a concentration gradient. Nitrocarburizing is done mainly to provide an antiscuffing surface layer and to improve fatigue resistance. Compare with carbonitriding.
An element that increases the strength, hardness and machinability of steel while decreasing its ductility and toughness. In aluminum killed steels, nitrogen combines with the aluminum to provide grain size control, thereby improving both toughness and strength. Nitrogen can reduce the effect of boron on the hardenability of steels.
Used in a numerical simulation to attach the adjacent elements.
Irregular particles having knotted, rounded or other, similar shapes.
Non Transferred Arc (Plasma)
The plasma arc which transfers heat energy to plasmagenic gas (argon, helium, hydrogen, nitrogen) in order to promote the plasma state according to Saha's law. This arc strikes between the tungsten electrode (cathode) and the constricting nozzle (anode). The term Pilot Arc is also used in plasma transferred arc processes (PTA welding).
Notched Coating Adhesion (NCA)
Nuclear Reaction Analysis (NRA)
An ion beam technique which profiles light-of-mass elements into materials. It analyses to a depth of up to one micrometer.
The initiation of a phase transformation at discrete sites, the new phase growing on nuclei.
The first structurally-stable particle capable of initiating the recrystallization of a phase or growth of a new phase while possessing an interface with the parent matrix. The term also applies to a foreign particle that initiates such action.
A quench-hardening treatment that entails the use of oil for cooling.
The type of quenching process that uses oil as a quenchant. Typically, an object being quenched in this way is made of carbon steel. Oils are categorized into conventional, fast, martempering, and hot quenching.
Films that affect the optical transmission or reflection of a surface. They are usually multilayer films, or stacks. They are generally composed of alternating layers of materials that have high (germanium [Ge], Si, TiO2, zirconium dioxide [ZrO2], SiO, cerium dioxide [CeO2]) and low (magnesium fluoride [MgF2], SiO2) indices of refraction. A major application is the antireflection (AR) coatings on lenses. Optical film stacks can be used as optical filters. Neutral density or gray filters reduce the light intensity equally for all wavelengths; broadband filters affect the transmission of radiation over a wide wavelength range, while narrow or monochromatic filters affect transmission over a very narrow wavelength region. Some film stacks are a special type of optical film whose color relates to the angle of observation (OVIDs). These films allow pseudo-holographic imaging. These OVID films are used as security devices to prevent counterfeiting. These films are an outgrowth of the interference-colored films used for decorative films and, when pulverized, for pigment.
An instrument for measuring the temperature of heated material by comparing the intensity of the emitted light with that of an incandescent lamp filament whose intensity is known.
A finish resembling the dimpled appearance of an orange peel.
A phase change among two solid solutions having the same crystal structure, but in which the atoms of one phase (disordered) are randomly distributed; in the other, the different kinds of atoms occur in a regular sequence upon the crystal lattice, which is in an ordered arrangement. Compare with dissociation.
Organic Metal Chemical Vapor Deposition (OMCVD)
An atmosphere analysis device in which gases are absorbed selectively (volumetric basis) by passing them through a series of preselected solvents.
Aging under conditions of time and temperature greater than those required to obtain maximum change in a certain property, resulting in the property being altered in the direction of the initial value.
Heating a metal or alloy to such a high temperature that its properties are impaired. When the original properties cannot be restored by further heat treating and/or mechanical working, the overheating is termed burning.
(1) A reaction in which there is an increase in valence resulting from a loss of electrons.
(2) A corrosion reaction in which the corroded metal forms an oxide; usually applied to reaction with a gas containing elemental oxygen, such as air.
Oxidized Surface (on steel)
Surface having a thin, tightly-adhering, oxidized skin (from straw to blue in color) that extends inwards from the edge of a coil or sheet. Sometimes called an annealing border.
A compound that causes oxidation, thereby causing itself to be reduced.
A gas flame produced with excess oxygen in the inner flame.
A coating composed of resin, a solvent, additives, pigments and sometimes a diluent. Paints are generally opaque, and commonly represent the portion of the industry known as the architectural coating industry.
An imprecise term used to denote a treatment given cold-worked material to either reduce the strength to a controlled level or relieve stress. For the term to be meaningful, one must state the type of material, the degree of cold work, and the time-temperature schedule.
A solid, tiny object that, together with other tiny objects, makes up a powder. This powder can be used for plasma spraying.
The elements, and their ratios to one another, that make up one particle.
Particle Size Distribution
The percentage by weight, or by number, of each fraction into which a powder sample has been classified with respect to sieve number or microns.
Particles Induced Gamma-ray Emission (PIGE)
An ion beam technique particularly well suited for the determination of light-mass element concentrations into materials. It can analyse to a depth of up to a few micrometers.
Particles Induced X-ray Emission (PIXE)
In wiremaking, a heat treatment applied to medium carbon or high-carbon steel before the drawing of wire or between drafts. This process consists of heating to a temperature above the transformation range and then cooling to a temperature below Ae1 in air or in a bath of molten lead or salt.
Perfluro Alkyle Ether (PFA)
A graphical representation of the temperature and composition limits of phase fields in an alloy system as they actually exist under the specific conditions of heating or cooling (synonymous with constitution diagram). A phase diagram may be an equilibrium diagram, an approximation to an equilibrium diagram, or a representation of metastable conditions or phases.
An element which is generally restricted to below 0.04 weight percent to minimize its detrimental effect on ductility and toughness. Certain steels may contain higher levels to enhance machinability, strength and/or atmospheric corrosion resistance.
Photothermal NDE (Non-Destructive Evaluation)
An NDE technique for sprayed coatings. A repeated pulse of heat, from a laser source, flows through the coating and substrate. The thermal signature is detected and related to the input signal, thereby indicating the thickness of the coating.
Properties of a metal or alloy that are relatively insensitive to structure and can be measured without the application of force. Example physical properties are density, electrical conductivity, coefficient of thermal expansion, magnetic permeability, and lattice parameter. Chemical reactivity is not a physical property. Compare with mechanical properties.
Physical Vapor Deposition (PVD)
An operation by which surface oxide (scale) is removed by chemical action. Sulfuric acid is typically used to pickle carbon and low-alloy steels. After the operation, which is carried out in an acid bath, the steel is rinsed in water.
A measuring device used to determine wear characteristics of material samples. A pin, which is a flat or spherical contact, is loaded with precisely-known force onto the disk, which is the test sample. The pin is mounted to a stiff lever designed to transduce force without friction. As the disk rotates, miniscule deflections of the lever (triggered by the action of frictional forces between pin and disk) are measured. Wear coefficients for both the pin and disk material are calculated from the volume of the material lost during a specific friction run. This simple method facilitates the determination and study of friction and wear behavior of almost every solid-state material combination, with variations in time, contact pressure, velocity, temperature, humidity, lubricants etc.
An instrument that measures the stagnation pressure of a flowing fluid, consisting of an open tube pointing into the fluid and also connecting to a device that indicates pressure.
The fourth state of matter. It is formed when a gas (usually argon, helium, nitrogen, hydrogen) has been heated to a temperature of sufficient heat to cause the gas to become partially ionized and therefore electrically conductive. The term was introduced by Irving Langmuir in 1930.
Plasma Assisted Chemical Vapor Deposition (PACVD)
This process allows coating via CVD to be carried out at greatly reduced temperatures. PACVD's temperature range lies between 150° and 250°C, whereas the temperature range for CVD is 800°–1000°C. The significance of this difference is that the variety of base materials that can be coated expands considerably.
See ion carburizing.
Plasma Enhanced Chemical Vapor Deposition (PECVD)
A jet of plasma usually produced from a plasma torch, which is a tool used to ionize gas (gas turns into a plasma when it is ionized) and then send it in the direction to which it is aimed. An electric arc is struck between a cathode and anode and is then blown through a nozzle to form this jet.
See ion nitriding.
Plasma Transferred Arc (PTA)
Another name for transferred arc.
Plasma-Based Ultra-Fine Particle Synthesis
A process wherein a liquid precursor is atomized and injected into the plasma flame. The plasma-synthesized particles are collected either as a deposit on a substrate or as a powder on an electrostatic precipitator.
Permanent distortion of metals. Plastic, as a descriptive word, is the opposite of elastic. This distortion is the result of stresses being applied to a metal and pushing the strain to beyond the material's elastic limit.
A space or chamber in a plasma torch, confined by the inner wall of the constricting nozzle and the cathodic electrode. The shape and size of this annular chamber play the highest role in plasma arc torches (welding, spraying).
The formation of grooves, by plastic deformation, in the softer of two surfaces in motion relative to one another.
A substance having large molecules consisting of repeated units. There are a number of natural polymers, such as polysaccharides, and synthetic polymers are used extensively in plastics.
Films of polymer. Interest is growing in regards to depositing organic and inorganic polymer films in vacuum. These films can be formed by condensation of a monomer, followed by E-beam or UV curing to polymerize the monomer, or by plasma polymerization of the monomer. The monomer precursor can yield a carbon, silicon or boron-based polymer material that often contains hydrogen, chlorine or fluorine. Films that contain fluorine are used to form hydrophobic surfaces.
A long chain polymer with orientated structure, providing low friction. It is applied as a coating (via spraying or dipping and curing) or as powder additions to other coatings (e.g. electroless nickel).
Another term for box annealing.
The transfer of molten metal from a furnace to a ladle, a ladle to another ladle, or a ladle to a mold.
Powder Gas Flow Rate
Powder Injection Angle
Precipitation Heat Treatment
A type of artificial aging in which a constituent precipitates from a supersaturated solid solution.
Heating that occurs before another thermal or mechanical treatment. It is done differently depending on the material and circumstances. Tool steel is preheated to an intermediate temperature immediately before final austenitizing. Some nonferrous alloys are heated to a high temperature for a long time to Homogenize the structure before working. In welding and related processes, heating is to an intermediate temperature for a short time immediately before welding, brazing, soldering, cutting, or thermal spraying.
A quench in which hot dies are pressed and aligned with a part before the quenching process begins. The part is then placed in contact with a quenching medium in a controlled manner. This process prevents distortion of the part.
A coating process wherein the coating contains no more than 12% solids by weight and at least .5% acid by weight and is used to provide surface etching. It is applied directly to metal surfaces to provide corrosion resistance, adhesion and ease of stripping.
An imprecise term denoting various treatments used to improve workability. For the term to be meaningful, one must state the condition of the material and the time-temperature cycle used.
A system of locating and tolerancing developed to control the orientation of rough parts in machine fixtures. From locating points on the casting, a "perfect profile" is established for all surfaces and features. A tolerance envelope surrounding that profile defines the limitations of an acceptable part.
Aliphatic hydrocarbon gas. It is used as a fuel gas in thermal spray processes.
(1) In a CFD simulation, fluid properties are density, viscosity and volume of expansion; particle properties are density and specific heat of evaporation.
(2) Properties are the characteristics of objects, substances, or processes that make these things unique. See mechanical properties and physical properties.
See blank carburizing.
See blank nitriding.
A type of continuous-type furnace in which parts to be heated are periodically charged into the furnace in containers, which are pushed along the hearth against a line of previously charged containers; thus advancing the containers toward the discharge end of the furnace where they are removed.
A device for measuring temperatures above the range of liquid thermometers.