Acm,
A1, A3, A4 Same
as Aecm, Ae1, and Ae3,
and Ae4.
Abradable
coatings Coatings which are designed to rub down against
the action of a mating surface to form a tight gas or air seal.
Abrasion
Resistance - Degree of resistance of a material to abrasion
or wear.
Abrasive
A substance used for grinding, honing, lapping, superfinishing,
polishing, pressure blasting or barrel finishing. It includes
natural materials such as garnet, emery corundum and diamond and
electric-furnace products like aluminum oxide, silicon carbide
and boron carbide.
Abrasive
blasting A pressurized stream of hard metal or oxide
grit material used to clean and / or roughen surfaces prior to
coating.
Abrasive
wear Wear caused by hard, sharp particles.
Accm,
Ac1, Ac3, and Ac4
Defined under transformation
temperature.
Acetylene
C2H2 - Unsaturated aliphatic
hydrocarbon gas. Used as a fuel gas in combustion thermal spray
processes, welding and cutting. Acetylene has the highest flame
temperature and requires the smallest amount of oxygen to form
a neutral flame.
Acicular
Ferrite A highly sub-structured conequiaxed ferrite
that forms upon continuous cooling by a mixed diffusion and shear
mode of transformation that begins at a temperature slightly higher
than the temperature transformation range for upper bainite. It
is distinguished from bainite in that it has a limited amount
of carbon available; thus, there is only a small amount of carbide
present.
Acoustic
emission Acoustic emissions are sound or ultrasound
pulses generated during crack initiation or propagation in materials
and coatings as a result of being subjected to stress. Acoustic
emissions can be detected by transducers.
Adhesion
- The ability of a coating to remain on the surface without spalling,
flaking or cracking. Adhesion is probably the single most important
property of a coating.
Adhesion
scratch test - Currently the most commonly used method
of assessing coating adhesion. Used in the analysis of organic
and inorganic soft and hard coatings. Examples are thin and multiplayer
PVD, CVD, PECVD, TD, photoresist, paints, lacquers, and many other
types of films, covering optical, micro-electronic, protective,
decorative and other applications. Substrates can be hard or soft,
including metals, alloys, semiconductors, glass, refractive and
organic materials. Scratch testing consists of introducing stresses
at the interface between coating and substrate. This is achieved
by pressing a diamond stylus on the sample surface with a normal
load FN. As the sample is displaced at constant speed,
the resulting stresses at the interface cause flaking or chipping
of the coating. The minimum load at which a specific failure event
is recorded is call the Critical Load (Lc). See Critical
Load.
Adhesive
Wear - Wear caused by sliding surfaces, where surface
asperities interact and adhere.
Aecm,
Ae1, Ae3, and Ae4
Defined under transformation
temperature.
Aerated
bath nitriding A type of liquid nitriding in which
air is pumped through the molten bath creating agitation and increased
chemical activity.
Age
hardening Hardening by aging, usually after rapid cooling
or cold working. See also aging.
Age
softening Spontaneous decrease of strength and hardness
that takes place at room temperature in certain strain hardened
alloys, especially those of aluminum.
Agglomerate
- Several particles adhering together.
Agglomerated
powder - A mechanically mixed combination of fine particles
of different materials held together with an organic binder and
formed into power particles.
Aging
A change in the properties of certain metals and alloys that
occurs at ambient or moderately elevated temperatures after hot
working or a heat treatment (quench aging in ferrous alloys, natural
or artificial aging in ferrous and nonferrous alloys) or after
cold working operation (strain aging). The change in properties
is often, but not always, due to a chemical composition of the
metal or alloy. See also age hardening,
artificial aging, interrupted
aging, natural
aging, overaging,
precipitation
hardening, precipitation
heat treatment, progressive
aging, quench
aging, step aging.
Air
Cap - A component of thermal spray guns used for shaping
the air flow for atomizing the wire or rod feedstock.
Air
classification - The separation of powder into particle
size fractions by means of an air stream of controlled velocity.
Air-hardening
steel steel containing sufficient carbon and other
alloying elements to harden fully during cooling in air or other
gaseous mediums from a temperature above its transformation range.
The terms should be restricted to steels that are capable of being
hardened by cooling in air in fairly large sections, about 2 in.
(50 mm) or more in diameter. Same as self-hardening
steel.
Alkyd
resin - A type of polyester resin used in paints and
other surface coating. The original alkyd resins were made by
copolimerizing phathalic anhydride with glycerol, to give a brittle
cross. Linked polymer.
Allotropy
A near synonym for polymorphism.
Allotropy is generally restricted to describing polymorphic behavior
in elements, terminal phases, and alloys whose behavior closely
parallels that of the predominant constituent element.
Alloy
A substance having metallic properties and being composed of two
or more chemical elements of which at least one is a metal.
Alloying
element An element which is added to a metal (which
remains within the metal) to effect changes in properties.
Alloy
steel - Steel containing specified quantities of alloying
elements (other than carbon and the commonly accepted amounts
of manganese, copper, silicon, sulfur, and phosphorus) within
the limits recognized for construction alloy steels, added to
effect changes in mechanical or physical properties.
Alpha
ferrite See ferrite.
Alpha
iron - The body-centered cubic form of pure iron, stable
below 910°C (1670°F).
Alumina
- Aluminum Oxide compound used in both abrasive blasting
as an abrasive and in thermal spraying as a consumable feedstock
(powder and rod) for the production of coatings. Alumina is a
hard wear resistance ceramic and can be alloyed with various amounts
of titania (titanium dioxide) to improve certain properties.
Aluminizing
(gas) -- High temperature (approx 900°C) pack or
gaseous diffusion of aluminum into the surface of a component
to enhance high temperature corrosion and oxidation resistance.
Aluminizing (hot dip) - A liquid aluminum submersion
technique at temperatures above 600°C depositing layer of
aluminum (usually on steel sheet) for enhance corrosion protection
Aluminizing
(thermal spray method) - Thermal sprayed coatings of
aluminum usually on substrates of steel or nickel chromium alloys
which are subsequently heat treated to aluminize the surface.
Aluminum
(Al) Used to deoxidize steel and control grain size.
Grain size control is affected by forming a fine dispersion with
nitrogen and oxygen which restricts austenite grain growth. Aluminum
is also an extremely effective nitride former in nitriding steels.
Aluminum
Ion Plating - The deposition of aluminum by a vacuum
evaporative process. Provides galvanic corrosion resistance. Normally
given a passivation treatment.
Amorphous
- Non-crystalline, or devoid of regular structure.
Anion
- A negatively charged ion.
Annealing
A generic term denoting a treatment, consisting of heating to
and holding at a suitable temperature followed by cooling at a
suitable rate, used primarily to soften metallic materials, but
also to simultaneously produce desired changes in other properties
or in microstructure. The purpose of such changes may be, but
is not confined to: improvement of machinability, facilitation
of cold work, improvement of mechanical or electrical properties,
and/or increase in stability of dimensions. When the term is used
without qualification, full annealing is implied. When applied
only for the relief of stress, the process is properly called
stress relieving or stress-relief annealing.
In ferrous alloys, annealing usually
is done above the upper critical temperature, but the time-temperature
cycles vary widely in both maximum temperature attained and in
cooling rate employed, depending on composition, material condition,
and results desired. When applicable, the following commercial
process names should be used: black
annealing, blue annealing, box
annealing, bright annealing,
cycle annealing,
flame annealing,
full annealing,
graphitizing,
intercritical
annealing, isothermal
annealing, malleablizing,
order hardening,
process annealing,
quench annealing,
spheroidizing,
subcritical
annealing.
In nonferrous alloys, annealing
cycles are designed to: (a) remove part or all of the effects
of cold working (recrystallization may or may not be involved);
(b) cause substantially complete coalescence of precipitates from
solid solution in relatively coarse form; or (c) both, depending
on composition and material condition. Specific process names
in commercial use are final
annealing, full
annealing, intermediate
annealing, partial
annealing, recrystallization
annealing, stress-relief annealing, anneal
to temper.
Annealing
carbon - Fine, apparently amorphous carbon particles
formed in white case iron and certain steels during prolonged
annealing. Also called temper
carbon.
Annealing
twin - A twin formed in a crystal during recrystallization.
Anneal
to temper - A final partial anneal that softens a cold
worked nonferrous alloy to a specified level of hardness or tensile
strength.
Anode
The positive electrode in a plasma spray torch (gun). Generally
made from copper but can be lined with tungsten to increase life.
See also cathode.
Anodic
coating -A coating that becomes the anode in an electrochemical
cell with the substrate (cathode). The only metals in common use
for thermal spraying which are anodic to iron and steel are zinc
and aluminum.
Anodizing
- The production of an oxide layer on aluminum alloys. The process
is electrolytic, a typical electrolyte being sulfuric acid. Treatment
at room temperature produces thin, decorative layers with some
corrosion protection. Treatment at 0°C produces hard, thicker
layers (up to 100µ) with wear resistance. They can be post
sealed to give improved corrosion resistance.
Antireflection
coating (AR coating) - A coating whose reflection is
zero, used for lenses. They are usually fabricated by the technique
of interference oscillations with a He-Ne laser.
Apparent
density - The weight of a unit volume of powder or coating
Apparent
hardness The value obtained by testing a coating or
sintered material with standard indentation hardness equipment.
See macro hardness.
Since the reading reflects a composite of pores and solid material,
(which may be particles relatively poorly bonded together) it
is usually lower than that of an equivalent solid wrought or cast
material. Not to be confused with particle hardness. See micro
hardness.
Arcm,
Ar1, Ar3, Ar4, Ar, Ar
Defined under transformation
temperature.
Arc
Blow (Plasma) - Arc blow is the deflection of an electric
arc under the influence of the magnetic field associated to the
flow of electrons (electric charge), which results in arc instability.
Arc blow can be reduced and minimized in plasma welding by an
appropriate design of shape and sizes of the electrodes (namely
cathode tip and anodic nozzle plenum).
Arc
Wire Spraying - A thermal spray process in which two
electrically conducting wires are brought together to form an
electric arc. The consequent molten metal is then projected by
an air stream towards the work piece to form a coating.
Argon
(Ar) - Monatomic noble gas, atomic number 18, one of
the most inert elements. Commonly used as a plasma gas for plasma
spraying and providing inert environments for many processes.
Artificial
aging Aging above room temperature. See aging.
Compare with natural
aging.
Athermal
transformation A reaction that proceeds without benefit
of thermal fluctuations; that is, thermal activation is not required.
In contrast, a reaction that occurs at constant temperature is
an isothermal
transformation; thermal activation is necessary in this case
and the reaction proceeds as a function of time.
As
cast - Referring to metal which has not received finishing
(beyond gate removal or sandblasting) or treatment of any kind
including heat treatment after casting. Similarly, as drawn, as
forged and as rolled.
Atomization
- The dispersion of a molten material into particles by a rapidly
moving gas or liquid stream or by mechanical dispersion.
Atomic
force microscopy (AFM) An extremely accurate and versatile
technique for measuring structures or surface forces. A very fine
sensor tip mounted to the end of a small deflecting spring, known
as a cantilever, is brought into contact with the sample surface
to be investigated. The sensor tip is moved across the surface
in numerous line scans. Due to the surface roughness (topography),
the tip and the cantilever move up and down. This movement can
be measured with high resolution and the resulting data allows
imaging of the surface structure. Also called scanning
probe microscopy.
Atomized
powder - A powder produced by the dispersion of a molten
material into particles by a rapidly moving gas or liquid stream
or by mechanical dispersion.
Atmosphere
- The gaseous environment in which the metal being treated is
heated for processing. Atmospheres are used to protect from chemical
change or to alter the surface chemistry of steel through the
addition or removal of carbon, nitrogen, hydrogen, and oxygen
and to add certain metallic elements as chromium, silicon, sulfur,
etc.
Auger
Electron Spectroscopy (AES) - An electron beam technique
applied for near-surface elements identification. well used in
thin film science.
Ausforming
Thermo mechanical treatment of steel in the metastable austenitic
condition below the recrystallization temperature followed by
quenching to obtain martensite and/or bainite.
Austempering
A heat treatment for ferrous alloys in which a part
is quenched from the austenitizing temperature at a rate fast
enough to avoid formation of ferrite or pearlite and then held
at a temperature just above Ms until transformation to bainite
is complete. Although designated as bainite in both austempered
steel and austempered ductile iron (ADI), austempered steel consists
of two phase mixtures containing ferrite and carbide, while austempered
ductile iron consists of two phase mixtures containing ferrite
and austenite.
Austenite
A solid solution of one or more elements in face-centered cubic
iron. Unless otherwise designated (such as nickel austenite),
the solute is generally assumed to be carbon.
Austenite
Steel - Any steel containing sufficient alloy to produce
a stable austenitic (gamma iron) crystalline structure at ambient
temperatures.
Austenitic grain size The size by the grains of steel when heated
to the austenitic region; may be revealed by appropriate etching
of cross sections after cooling to room temperature.
Austenitizing
Forming austenite by heating a ferrous alloy into the transformation
range (partial austenitizing) or above the transformation range
(complete austenitizing). When used without qualification, the
term implies complete austenitizing.
Autoclaving
- The production of a stable, protective oxide on steel parts
by treatment in a pressurized, high temperature steam containing
atmosphere.
Bainite
A metastable aggregate consisting of dispersed carbide in ferrite
resulting from the transformation of austenite at temperatures
below the pearlite range but above Ms. Its appearance is in the
form of relatively coarse ferrite laths between which carbides
are precipitated as platelets if formed in the upper part of the
bainite transformation range; acicular, resembling tempered martensite,
if formed in the lower part.
Bainitic
hardening Quench-hardening treatment resulting principally
in the formation of bainite.
Banded
structure - A layering effect that is sometimes developed
during the hot rolling of steel.
Bark
- An older term used to describe the decarburized skin that develops
on steel bars heated in a non-protective atmosphere.
Base
coats for electroplating - Materials that are difficult
to electroplate because of rapid oxide formation can have an adherent
base coat applied by PVD processes and then the coating built-up
by electrodeposition. Examples are plating on titanium, uranium,
and zirconium where a base coat of a material like nickel or copper
is applied by a PVD process before the electroplated coating is
built up.
Batch
furnace A furnace used to heat treat a single load
at a time. Batch-type furnaces are necessary for large parts such
as heavy forgings and are preferred for complex alloy grades requiring
long cycles. See car
furnace, horizontal
batch furnace.
Belt
furnace A continuous-type furnace which uses a mesh-type
or cast-link belt to carry parts through the furnace.
Beta
annealing Producing a beta phase by heating certain
titanium alloys in the temperature range of which this phase forms
followed by cooling at an appropriate rate to prevent its decomposition.
Billet
- A solid semi finished round or square that has been
hot worked usually smaller than a bloom. Also a general term for
wrought starting stock for forgings or extrusions.
Binder
- A cementing medium used in producing composite or agglomerate
powders.
Black
annealing Box annealing or pot annealing ferrous alloy
sheet, strip, or wire to impart a black color to the oxidized
surface. See box annealing.
Black
oxide A black finish on a metal produced by immersing
it in hot oxidizing salts or salt solutions.
Blackadizing
- A pressurized stream of some materials (Glass, plastic, metal,
ahs, etc) applied on a surface to clean and/or roughen. It can
be, depending on the media, abrasive or non-abrasive.
Blank
annealing Simulating the carburizing operation without
introducing carbon. This is usually accomplished by using an inert
material in place of the carburizing agent, or by applying a suitable
protective coating to the ferrous alloy.
Blank
Carburizing - Simulating the caruburizing operation without
introducing carbon. This is usually accomplished by using an inert
material in place of the carburizing agent, or by applying a suitable
protective coating to the ferrous alloy.
Blank
nitriding Simulating the nitriding operation without
introducing nitrogen. This is usually accomplished by using an
inert material in place of the nitriding agent or by applying
a suitable protective coating to the ferrous alloy.
Blasting
- A pressurized stream of particulates (ceramic, plastic, metal,
etc.) applied on a surface to clean, peen or abrade.
Blended
Powder - A powder consisting of two or more different
powder materials thoroughly mixed.
Bloom
- A semi-finished hot rolled rectangular product. The
width of the bloom is no more than twice the thickness and the
cross-sectional area is usually not less that 36 square inches.
Blue
annealing Heating hot-rolled ferrous steel in an open
furnace to a temperature within the transformation range and then
cooling in air, in order to soften the metal. The formation of
a bluish oxide on the surface is incidental.
Blue
brittleness Brittleness exhibited by some steels after
being heated to some temperature within the range of about 205
to 370°C (400 to 700°F), particularly if the steel is
worked at the elevated temperature. Killed steels are virtually
free of this kind of brittleness.
Bluing
Subjecting the scale-free surface of a ferrous alloy to the
action of air, steam, or other agents at a suitable temperature,
thus forming a thin blue film of oxide and improving the appearance
and resistance to corrosion. Note: This term is ordinarily applied
to sheet, strip, or finished parts. It is used also to denote
the heating of springs after fabrication to improve their properties.
Bond
- This represents the state of adhesion between the coating
and the substrate. Its strength will depend on the details of
the thermal spraying process and the materials used. Bonding mechanisms
may be mechanical, physical or metallurgical or a combination
of these.
Bond
coat - A coating applied as an intermediary between the
main or top coating and the substrate in order to improve the
bond strength.
Bond
strength - The strength of the adhesion between the coating
and the substrate. A number of test methods are in use to measure
the bond strength of coatings.
Boriding
Thermo chemical treatment involving the enrichment of the surface
layer of an object with borides. This surface-hardening process
is performed below the Ac1 temperature.
Boron
(B) - is usually added between .0005-.003% to significantly
increase the hardenability, especially for low carbon alloys.
It does not affect the strength of ferrite, therefore not sacrificing
ductility, formability or machinability in the annealed state.
Boronizing
- The diffusion of boron into the surface of a component (usually
steel) by a high temperature (approx. 900°C) gas or pack process.
Produces hard phases within the surface (Typically 100µm
deep).
Boundary
condition - The loads, displacements, temperatures, densities
etc. at the periphery of the domain or mesh in a numerical simulation.
Box
annealing Annealing a metal or alloy in a sealed container
under conditions that minimize oxidation. In box annealing a ferrous
alloy, the charge is usually heated slowly to a temperature below
the transformation range, but sometimes above or within it, and
is then cooled slowly; this process is also called close annealing
or pat annealing. See black annealing.
Breaks
Creases or ridges usually in untempered or in aged material
where the yield point has been exceeded. Depending on the origin
of the break, it may be termed a cross break, a coil break, an
edge break, or a sticker break.
Bright
annealing Annealing in a protective medium to prevent discoloration
of the bright surface. Compare with blank
nitriding.
Brinell
hardness test A test for determining the hardness of
a material for forcing a hard steel or carbide ball of specified
diameter into it under a specified load. The result is expressed
as the Brinell hardness number, which is the value obtained by
dividing the applied load in kilograms by the surface area of
the resulting impression in square millimeters.
Brine
quenching A quench in which brine (salt water-chlorides,
carbonates, and cyanides) is the quenching medium. The salt addition
improves the efficiency of water at the vapor phase or hot stage
of the quenching process.
Brittle
fracture Separation of a solid accompanied by little
or no macroscopic plastic deformation. Typically, brittle fracture
occurs by rapid crack propagation with less expenditure of energy
than for ductile
fracture.
Brittle
tempering range - Some hardened steels show an increase
in brittleness when tempered in the range of about 450°F to
700°F even though some tempering causes some softening.
Burning
(1) Permanently damaging a metal or alloy by heating to cause
either incipient melting or intergranular oxidation. See overheating,
grain-boundary
liquidation. (2) In grinding, getting the work hot enough
to cause discoloration or to change the microstructure by tempering
or hardening.
