The flow regime which exists when the Reynolds Number is below 2000. The path lines of the particles are smooth and regular, and there is little interchange of fluid mass between adjacent layers.
A surface imperfection which appears as a seam. It is caused by the folding over of hot metal, fins, or sharp corners and then rolling or forging them into the surface but not welding them. Laps on tubes can form from seams on piercing mill billets.
A deposition technique which uses a pulsed UV laser beam for vaporizing solid source materials. Much of the material ablates as macroparticles rather than vaporizing as atoms or molecules. A key advantage is that it can achieve congruent evaporation of complex materials, such as mixed oxides.
The melting and quenching of a surface to form a fine-grained structure, or ‘glaze’.
A surface-hardening process which uses a laser to quickly heat a surface above 900°C. Heat conduction into the interior of the part will quickly cool the surface, leaving a shallow layer of martensite.
Thermal energy that is absorbed or released when a substance undergoes a phase change.
An element that improves machinability. It does not dissolve in steel but stays instead as globules. As a result of environmental concerns, the use of lead in the steel industry has decreased.
Slower-than-usual cooling rates, associated with a hot vapor blanket that surrounds a part being subjected to quenching in a liquid medium. The gaseous vapor envelope acts as an insulator, thus slowing the cooling rate.
Liquid Impingement Erosion
The progressive loss of material from a solid surface due to continued exposure to impact from liquid drops or jets.
Liquid Spray Quench
Synonymous with spray quenching.
Precipitation from a supersaturated solid solution, similar to continuous precipitation, except that the precipitate particles form at preferred locations such as along slip planes, grain boundaries, or incoherent twin boundaries.
Low Activation Interior Coating
Low Pressure Plasma Spraying (LPPS)
Plasma spraying carried out in a chamber which has been evacuated to a low partial pressure of oxygen. It is then usually partially backfilled with argon to avoid the possibility of forming a glow discharge.
Magnetic Storage Media
Whether magnetic materials are classified as “hard” or “soft” depends on how hard it is to reverse the polarity of, magnetize or demagnetize the magnetic field. Soft magnetic materials, such as the Permalloys (iron [Fe]:40–80% Ni) and Y2Fe5O12 (garnet), are used in memory storage devices where the data are changed often. Hard magnetic materials, such as Fe3O4, Co:Ni:tungsten [W], Co:rhenium [Re], gadolinium [Gd]:Co, and Gd:terbium [Tb]:Fe, are used in more permanent recording media, such as audio tapes. Various techniques are used to define the magnetic domains that act as the storage sites.
A method used to test the heat extraction rates of various quenchants. The test works by utilizing the change in magnetic properties of metals at their Curie point, or the temperature above which metals lose their magnetism.
A synonym for sputtering.
Malleable Cast Iron
A cast iron made by the prolonged annealing of white cast iron (in which decarburization and/or graphitization eliminate some or all of the cementite). The graphite is in the form of temper carbon. If decarburization is the predominant reaction, the product will exhibit a light fracture surface—hence the name “whiteheart malleable”. Otherwise, the fracture surface will be dark (blackheart malleable). Ferritic malleable has a predominantly ferritic matrix. Pearlitic malleable may contain pearlitic, spherodite or tempered martensite, depending on heat treatment and the desired hardness.
An element that deoxidizes the melt and facilitates the hot working of steel by reducing its susceptibility to hot shortness. It combines with sulfur to form MnS stringers, which aid machinability. Manganese contributes to the effectiveness of normalizing for strengthening and to the formation of fine pearlite. It also lowers the M
s Temperature, which increases the probability that some austenite will be retained.
Any coating, excepting unsaturated polyester resin (fiberglass) coatings, that contains volatile organic materials. It is applied to ships, boats, and their appurtenances, buoys and oil drilling rigs intended for the marine environment.
See martempering below.
(1) A hardening procedure in which an austenitized, ferrous work piece is quenched in an appropriate medium whose temperature is equal to the M
s of the work piece, held in the medium until its temperature is uniform throughout (but not long enough to permit the formation of bainite) and then cooled in air. The treatment is frequently followed by tempering.
(2) When the process is applied to carburized material, the controlling M
s Temperature is that of the case. This variation of the process is frequently called marquenching.
A generic term for microstructures formed by diffusionless phase transformation in which the parent and product phases have a specific crystallographic relationship. Martensite is characterized by an acicular pattern in the microstructure in both ferrous and nonferrous alloys. In alloys where the solute atoms occupy interstitial positions in the marensite lattice (such as carbon in iron), the structure is hard and highly strained; but where the solute atoms occupy substitutional positions (such as nickel in iron), the martensite is soft and ductile. The amount of high-temperature phase that transforms to martensite on cooling depends to a large extent on the lowest temperature attained, there being a rather distinct beginning temperature (M
s) and a temperature at which the transformation is essentially complete (M
Martensitic Stainless Steels
The effect that the mass of a component has on the properties of the material from which the part is made. In castings, such effects may arise due to the effect of mass on solidification and on the rate of temperature change heat treatment.
The properties of a material that describe its elastic and inelastic behavior when force is applied, thereby indicating its suitability for mechanical applications. For example: modulus of elasticity, tensile strength, elongation, hardness, fatigue limit. Compare with physical properties.
Any effort to determine a material's mechanical properties.
The area made up of elements and nodes (or grid points) in a numerical simulation.
An opaque and lustrous elemental chemical substance that is a good conductor of heat and electricity and which, when polished, is a good reflector of light. Most elemental metals are malleable and ductile, and are generally denser than other elemental substances.
The natures, distributions and amounts of the metallographic constituents in a metal.
Produced either by chemical bonding between areas of the coating and substrate that are in intimate contact or by diffusional interaction between the coating and substrate. Metallurgical bonding can be enhanced by post-diffusion heat treatments.
The science and technology of metals and alloys. Process metallurgy is concerned with the extraction of metals from their ores and with refining of metals; physical metallurgy with the physical and mechanical properties of metals as affected by composition, processing and environmental conditions; and mechanical metallurgy with the responses of metals to applied forces.
A micrograph is produced when a section of the coating is taken, polished to show the particulate layers, and then photographed through a microscope.
The hardness of a material as determined by forcing an indenter, such as a Vickers or Knoop indenter, into the surface of a material under very light load; usually, the indentations are so small that they must be measured with a microscope. Capable of determining hardness of different microconstituents within a structure, or a measuring steep hardness gradients such as those encountered in case hardening.
One millionth of an inch; 0.000001”.
One millionth of a meter; 0.001 mm.
Residual stresses that vary from tension to compression in a distance (presumably approximating the grain size) that is small compared with the gage length in ordinary strain measurements. They are not detectable by dissection methods, but can sometimes be measured from the line shift or line broadening in an x-ray diffraction pattern.
Segregation within a grain, crystal, or small particle.
The structure of a metal as revealed at high magnification, usually at 100× and higher.
A device for measuring powder particle size distributions.
One thousandth of an inch; 0.001”.
The portion of a powder sample that passes through a standard sieve of a specified number. Contrast with plus sieve.
Modulus Of Elasticity (E)
In tension, it is the ratio of stress to the corresponding strain within the limit of elasticity (Yield Point) of a material. For carbon and low alloy steels of any composition and treatment, the value is approximately 200 GPa or 30,000,000 psi.
Modulus of Resilience (Ur)
The amount of strain energy per unit volume required to stress a material from zero to the yield stress limit. The modulus of resilience is proportional to the area under the elastic portion of the stress-strain diagram. Units are Pa or psi.
Modulus of Rigidity
Modulus of Rupture
Used in both bending and torsion testing. In bending, the modulus of rupture is the bending moment at fracture divided by the section modulus. In torsion, modulus of rupture is the torque at fracture divided by the polar section modulus.
Modulus of Toughness (Ut)
Mold Coating (Mold Facing, Dressing)
An element with atomic number 42. It increases the hardenability of steels, helps maintain a specified hardenability, and increases high temperature tensile strength and creep strength. Molybdenum hardened steels require higher tempering temperatures for softening. It is used as an alloying element for other metals and as a hardening element for steels and diecasting dies. Its melting point is 2620°C (4748°F).
Molybdenum Disulphide (MoS2)
The ability of a solid to exist in two or more forms (crystal structures), one of which is the stable modification at all temperatures and pressures. For example, ferrite and martensite are a monotropic pair below Ac1in steels. Its alternate spelling is monotrophism.
Multiport Nozzle (Plasma)
A constricted nozzle with two or more internal bores. This distinction's purpose is to provide more control over the shape and stability of a plasma arc.