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Glossary of MinSE


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B

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The usual configuration of sputter deposition, whereby a negative bias is applied to the substrate during sputter deposition, the purpose of which is to raise the substrate ion density, causing heating and much improved coating adherence. The chamber walls are held at positive-ground potential. The magnitude of the substrate negative bias depends upon the type of sputter source and the point of time in the coating cycle. At the commencement of the treatment, a large negative bias (≈1000 volts) maybe applied to effect a "clean-up" of the components surfaces, through glow discharge sputtering. At the commencement of sputter deposition, the substrate bias voltage is reduced: (i) for a conventonal balanced magnetron source to ≈500 volts; (ii) for a modern unbalanced source to ≈ 50 - 200 volts. Also see balanced magnetron and unbalanced magnetron.
Hungary flag
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(i) The main component of a polymeric coating material, which binds the pigment and filler particles together and creates a durable bond with the substrate. Also known as a film former. (ii) The metallic Co phase in WC-Co spray deposited coatings.
Hungary flag Kötőanyag
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A surface finishing process leading to the formation of a thin black oxide film on the surface of a metallic object, performed with the aim of improving corrosion resistance, usually for decorative applications. Steel objects are most frequently blackened in an oxidizing bath or furnace.
Hungary flag Feketedés
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A technique of non-eqilibrium carburising to enable rapid carbon transfer. See vacuum carburising and plasma carburising.
Hungary flag Gyors-diffúz kör
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This thermochemical treatment involves diffusing interstitial boron into (mainly) steel or cemented carbide components at a temperature such that highly durable surface mono- or multi-layers of transition metal borides are formed through a reaction between the boron and one or more metals in the substrate. For steels, treatment temperatures are in the range of 750 to 1050°C; for cemented carbides temperatures are ≈1000°C. Other substrates, like titanium and nickel base alloys can be treated in principle but industrial boriding of these alloys is comparatively rare. Various boriding media are available: plasma, gas, salt bath (electroless and electrolytic), pack and paste. Salt bath media are mainly exploited in Eastern Europe; their negative environmental draw backs has prevented wider exploitation in Western Europe, North America and Japan. The main-stay technique outside Eastern Europe remains the pack process, despite notable development efforts in gaseous and plasma boronizing. A common pack comprises (by weight) 90% SiC, 5% B4C and 5% KBF4. The SiC acts as a diluent, the B4C acts as the principal boron source while the KBF4 serves as an activating and fluxing agent. The latter can be satisfactorily replaced by NH4Cl. Boriding has the ability to convey improvements in wear resistance while simultaneously imparting resistance to corrosion by mineral acids and molten metals (especially zinc and aluminium). Boride layers produced through boriding tend to lack the toughness required for high contact loads especially those delivered at high strain rates; in this regard they are inferior to nitrided or carburised steels. The duplex FeB/Fe2B produced on boriding steels, under moderate boron potential, results in the creation of detrimental residual elastic stresses in the vicinity of the FeB/Fe2B interface. This is one factor that is responsible for the observed brittleness of borided surfaces. In the case of plain carbon and low alloy steels, boride layer toughness can be improved by boriding under low boron potential to produce a mono-phased layer of Fe2B. Another possibility is to conduct a post boriding annealing treatment ≈850°C, in vacuo, thereby converting the duplex FeB/Fe2B into a mono-phased Fe2B layer. The latter option is obviously less economic.
Hungary flag Boridálás
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See gaseous carburising
Hungary flag Boudouard reakció
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Any lubricant that serves to enable stable boundary lubrication. If the lubricant fails, seizure will result. Boundary lubricants are often added to oils as "additives". Various types exist, which include hexadecanol, oleic acid amide and stearic acid.
Hungary flag Határ kenőanyag
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A condition taking place in lubricated machine components where two sliding bearing surfaces pass over each other but are prevented from making metal on metal contact by a very thin boundary film of organic lubricant. It is argued that the film may only be a few molecules or even one molecule thick. This condition only arises under very high contact pressures or when sliding speeds are low. An example of this is the die-workpiece interface in wire drawing.
Hungary flag Határ kenés
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A bainite-like decomposition product of Fe-N austenite, induced by appropriate isothermal cooling, after austenitic nitriding.
Hungary flag Braunit
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A ball of WC-Co is pressed by a heavy load (often 3,000 kg) into the surface of a metal and the diameter of the depression is measured. The Brinell Hardness Number (BHN) is the ratio of the load (kg) to surface area (mm2) of the indentation, hencethe units are actually in kg/mm2. Both macro and microindentation versions exist. The technique is widely used in the steel heat treatment sector. Named after J. A. Brinell (1849-1925).
Hungary flag Brinell keménység

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