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Glossary of MinSE



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Fluidized beds can be used to provide rapid thermochemical diffusion treatments; since heat transfer is rapid the time to achieve the required treatment temperature is shorter than for many other thermochemical diffusion methods (except salt bath methods).   The most common examples where fluidized bed technology is exploited are nitroarburising, nitriding and carburising; boriding has also received investigation but is not very commonly practised.   All these processes utilise a fluidised bed of inert material (often aluminium oxide - corundum) through which appropriate gases (similar to those already described for the equivalent gaseous treatments) are passed.    Fluidised-bed operations are intrinsically dusty and stringent working practices are required in order to maintain an acceptable level of workshop cleanliness.

Hungary flag Fluid-ágyas termokémiai diffúzós módszerek

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In the context of surface engineering, the ability of a plastic or metallic coating to adapt to changes in shape without flaking or cracking.   A common quality required of coated steel sheet.

Hungary flag alakíthatóság

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A relatively low cost method of applying polymeric coatings (>200 µm thick) to metals, especially steels.   The workpieces are preheated and immersed into a bed comprising fluidised polymeric particles, which melt on coming into contact with the pre-heated surfaces, thereby forming a dense polymeric coating.  The technique requires significant operator skill.   Before coating, it is important to vapour degrease and grit blast the component surfaces, followed by phosphating or chromating.  Also see electrostatic fluidized-bed coating  and electrostatically sprayed plastic coatings

Hungary flag Fluid-ágyas bevonatolás műanyagokkal

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Sometimes called shorterizing.   A convenient method of transformation hardening, requiring less capital investment than induction hardening.   Oxyacetylene or oxygen-propane gas torch(es) provide the required heating to raise the surface temperature of medium carbon steels (≈0.3-0.5wt-%C) into the austenitic range; susbsequently the heated parts are quenched by spraying with water jets or by immersion in a quench tank, thereby developing the required martensitic case.    There are three main types of flame hardening:  (i) manual hardening comprises heating the objects to be hardened with a hand held torch. This method is useful for hardening small surface areas and small numbers of parts; (ii) spin hardening is employed for components with rotational symmetry; here the torches are mechanically fixed while the components are rotated on a motorised platform-fixture; (iii) progressive hardening is used for hardening flat surfaces or long sections, like machine slide-ways.   The torch is passed over the surface, or the part is passed under a fixed torch,  at speeds ≈50 to 200 mm/min.   Immediately located behind the torch is a cold water jet which provides the quench medium.  Also see induction hardening.

Hungary flag lángedzés

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A term widely used in the electronics  industries relating to thin (usually  <1 µm) coatings applied to so called thin-film devices.   Such coatings are frequently insulating or semi-conducting in their electrical character.

Hungary flag film

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A well established computational technique for determining the distribution of stresses in engineering structures under load.  FEM has found recent use in surface engineering for  the prediction of elastic stresses in low modulus metals coated with high modulus ceramic coatings during point contact loading.

Hungary flag Végeselem módszer (F.E.M.)

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A device, such as an electron beam or electric arc, used to vapourise the solid source component of a coating in evaporative source PVD.   

Hungary flag párologtató berendezés

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See spalling

Hungary flag rétegszétválasztás

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(i)  a shallow chemical cleaning aimed at removing surface oxides or passive films by immersion in an appropriate acid or alkaline solution;  (ii) a glow discharge cleaning process for the removal of passive oxide layers; usually achieved more efficiently with an RF rather than a DC plasma.  Plasma etching is frequently a preparatory step before plasma assisted PVD.

Hungary flag maratás

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Wear taking place by the mechanism of erosion.  Commonly found in soil engaging tools, hydro-electric plant, beach-landing marine craft and aircraft components operating in desert environments

Hungary flag Eróziós kopás


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