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Glossary of MinSE


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N

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A recent method of microhardness or ultramicrohardness using very small indentation loads ≈10µN to 5mN in conjunction with a Berkovich (triangular base pyramid) diamond indenter.   Machines record the penetration depth as a functin of indenter displacement.  The technique is able to determine the hardness of very thin coatings (<1µm thick); from the slope of the load-unload curves elastic moduli can also be derived.   A disadvantage of technique is its high sensitivity to sample surface roughness.

Hungary flag Nano-benyómódás keménység

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A solid-state laser in which an yttrium-aluminium-garnet (YAG) crystal, doped with neodymium (Nd) ions, constitutes the laser active medium.  With this laser it is possible to achieve laser pulses of a very short duration (several ns) each being of extremely high power (up to 1 GW).   Hence, this laser is ideally suited for laser glazing.

Hungary flag Nd-YAG lézer

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An electroplating process in which nickel is deposited from a Watts, sulphamate or fluoborate bath.  Nickel electroplating is applied for corrosion protection, primarily to steel but also brass and zinc.  To a minor degree it is also used for decorative purposes.   Also see electroless nickel plating.

Hungary flag nikkelezés

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The ability of a material, usually a steel, to increase its surface hardness by the solution of nitrogen.   For steels, it is essential they contain elements that develop coherent nitride precipitates during nitriding.  Typically, these elements are Cr, Mo, Ti, V and Al.   Nitridability also refers to the rate of nitride case development.    A steel of high nitridability is one which develops a nitrided case of significant thickness, at a given temperature, after a relatively short time.

Hungary flag Nitridálási képesség

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Thermochemical diffusion treatment involving the enrichment of a metallic surface with nitrogen.  Plasma, gaseous and salt bath media can be used.   Due to its dependence on cyanide based salts, the latter is now less widely practised.

Hungary flag Nitridálás

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Low alloy steels typically containing ≈0.25 wt-%C and 3.0 wt-% Cr with minor additions of molybdenum (≈0.50 wt%).   Among the most popular types of nickel-chromium-molybdenum steels are BS970:722M24.  Chromium can be reduced and replaced by aluminium.   This serves to enable higher prior tempering tempertures, without impairing nitridability. (Note: chromium carbide precipitation is significant on tempering above 550°C; such chromium is not able to participate in subsequent nitriding reactions.   Hence the virtue of aluminium bearing steels like BS970:905M31.) 

Hungary flag Nitridáló acélok

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A thermochemical diffusion treatment applied to plain carbon steels whilst in the ferritic state.  Nitrogen (the major solute) and carbon (the minor solute) are simultaneously diffused into the steel surface at temperatures ≈550-590°C for times that are typically less than 3 hours.   The treatment produces an external compound layer comprising mainly e-Fe2-3N although some g'-Fe4N may also exist as a minor constituent.  Small increases in fatigue strength and endurance can be achieved by developing compressive residual stresses in the diffusion zone beneath the compound layer.  This is achieved by  quenching the components into water or an oil/water emulsion after completion of the diffusion stage.     Although first popularised as a cyanide based salt-bath technique, environmental legislation has lead to significant developments in gaseous (see Nitrotec and NitrotecS ) and plasma nitrocarburising methods.   These are now replacing salt bath methods.

Hungary flag cementálás

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Variation in nitrogen distribution as a function of depth below the surface.

Hungary flag Nitrogén eloszlás

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Any coating that inhibits sticking or fouling by solids or suspended solids.    Apart from obvious domestic applications, such coatings are often applied to the internal surfaces of pipes used in the dairy and food processing industries for the conveyance of food products.   Sometimes known as "release coatings".    Also see PTFE coating.

Hungary flag Nem-ragadó bevonat


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