Glossary | Q & R (The vocabulary of the coating and heat-treating industries—explained)

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Quality Control (QC)

All aspects of the control of the spraying process, including the surface preparation, spraying, control of thickness deposited and the oxide and porosity levels, surface finish and NDE checks, as specified.

Quarter Hard

A temper of nonferrous alloys and some ferrous alloys, characterized by tensile strength about midway between that of dead soft and half hard tempers.

Quench-Age Embrittlement

Embrittlement that affects low-carbon steels as a result of precipitation of solute carbons at existing dislocations and from precipitation hardening of the steel. It is caused by rapid cooling of the steel from temperatures slightly below Ac1, and can be minimized by quenching from lower temperatures.

Quench Aging

Aging induced by rapid cooling after solution heat treatment.

Quench Annealing

Annealing an austenitic, ferrous alloy by solution heat treatment followed by rapid quenching.

Quench Crack

(1) A crack resulting from thermal stress induced during rapid cooling or quenching, or from stresses induced by delayed transformations some time after the article has been fully quenched.
(2) The fracture of a metal during or resulting from quenching from elevated temperature. Most frequently observed in hardened carbon steel, alloy steel, or tool steel parts of high hardness and low toughness. Cracks often emanate from fillets, holes, corners, or other stress raisers and result from high stresses due to the volume changes accompanying transformation to martensite.

Quench Hardening

(1) Hardening suitable alpha-beta alloys (most often certain copper to titanium alloys) by solution treating and quenching to develop a martensitic-like structure.
(2) In ferrous alloys, hardening by austenitizing and then cooling at a rate such that a substantial amount of austenite transforms to martensite.


Rapid cooling. When applicable, the following more specific terms should be used: brine quenching, caustic quenching, cold die quenching, forced-air quenching, intense quenching, oil quenching, press quenching, spray quenching, direct quenching, fog quenching, hot quenching, interrupted quenching, and water quenching.



To place parts that will be heat treated onto a rack or tray. This is done to keep parts in a proper position, to avoid heat-related distortions and to keep parts separated. See fixturing.


A phenomenon associated with the transformation of gamma iron to alpha iron on cooling (supercooling) of iron or steel, and which is revealed by the brightening (reglowing) of the metal surface. The reglowing is caused by a sudden increase in temperature due to the fast liberation of the latent heat of transformation. Contrast with decalescence.


(1) To increase the carbon content of molten cast iron or steel by adding carbonaceous material, high-carbon pig iron, or a high-carbon alloy.
(2) To carburize a metal part to return surface carbon lost in processing; also known as carbon restoration.


The reduction or removal of work-hardening effects, without motion of large-angle grain boundaries.


(1) The formation of a new, strain-free grain structure from that existing in cold-worked metal; usually accomplished by heating.
(2) The change from one crystal structure to another, as occurs upon heating or cooling through a critical temperature.

Recrystallization Annealing

Annealing cold-worked metal to produce a new grain structure without phase change.

Recrystallization Temperature

The approximate minimum temperature at which complete recrystallization of a cold-worked metal occurs within a specified time.


Equipment for transferring heat from gaseous products of combustion to incoming air or fuel. The incoming material passes through pipes surrounded by a chamber through which the outgoing gases pass.

Reducing Agent

A substance that causes reduction, thereby itself becoming oxidized.

Reducing Flame

A gas flame produced with excess fuel in the inner flame.


A reaction in which electrons are added to the reactant. More specifically, the addition of hydrogen or the abstraction of oxygen.

Reduction of Area

(1) Commonly, the difference, expressed as a percentage of original area, between the original cross-sectional area of a tensile test specimen and the minimum cross-sectional area measured after complete separation.
(2) The difference, expressed as a percentage of original area, between original cross-sectional area and that after straining of the specimen.


(as a substance) A material of very high melting point with properties that make it suitable for such uses as furnace linings and kiln construction.
(as a descriptive word) The quality of resisting heat.


Similar to a recuperator, the differences being that the gaseous products of combustion heat brick checkerwork are in a chamber connected to the exhaust side of the furnace, while the incoming air and fuel are being heated by the brick checkerwork in a second chamber connected to the entrance side. At intervals, the gas flow is reversed so that incoming air and fuel contact hot checkerwork while that in the second chamber is being reheated by exhaust gases.

Residual Stress

An internal stress independent of external forces and which results from such factors as cold working, phase changes and temperature gradients.


Either a synthetic polymer or one that occurs naturally.


A vessel used for the distillation of volatile materials, as in the separation of some metals and in the destructive distillation of coal.

Reverberatory Furnace

A furnace with a shallow hearth, usually nonregenerative, and which has a roof that deflects the flame and radiates heat toward the hearth or the surface of the charge.

RFI (Radio Frequency Interference) Shielding

Thermal spray coatings of electrically conductive metals—such as zinc, aluminum and copper—that are used on non-conducting, composite casing materials to shield sensitive electronic devices from radio frequency electromagnetic interference.

Rhodium Plating

The electrodeposition of rhodium to provide oxidation resistance and increased surface hardness.

Rimmed Steel

A low-carbon steel with enough iron oxide to give a continuous evolution of carbon monoxide during solidification, producing a rim of material that is virtually free of voids.

Rockwell Hardness Test

An indentation hardness test based on the depth of penetration of a specified penetrator into the specimen under certain arbitrarily fixed conditions.

Rotary Retort Furnace

A continuous-type furnace in which the work advances by means of an internal spiral, which gives good control of the retention time within the heated chamber.


(defect) A casting defect caused by incomplete filling of the mold due to molten metal draining or leaking out of some part of the mold cavity during pouring.
(process) The escape of molten metal from a furnace, mold or melting crucible.

Rutherford Backscattering Spectrometry (RBS)

A relevant ion beam technique for analyzing surface composition (analyzed depth of up to 1 micrometer). It is widely used in thin film science.

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