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Glossary of MinSE


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D

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Any process that produces a surface enriched in another element through solid state diffusion and (usually) resulting in the formation of intermetallic or interstitial compounds.  Processes include aluminising, boriding, chromising, sheradising, siliconising  and vanadising.  By convention, it specifically excludes carburising, carbonitriding, nitriding, and nitrocarburising.

Hungary flag Diffúziós bevonat

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That time of a thermochemical treatment when the active specie(s) diffuse into the substrate.   To provide distinction from, for example, the heating and cooling cycles.

Hungary flag Diffúziós idő

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The concentration of elements in the diffusion zone following a thermochemical diffusion treatment.  Also see concentration profile.

Hungary flag Diffúziós eloszlás

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A  term first invoked by Trent and Loladze in the 1950's, to account for the rake face cratering of cemented carbide cutting tools, observed after cutting plain carbon and low alloy steels at relatively high speed (>100m/min). Other workers have termed this effect "dissoution/diffusion wear" or "solution wear".  For cemented carbide tools, comprising WC-Co or WC-(W,Ti, Ta,Nb)C-Co (termed "straight grade" and "steel cutting grade" carbides respectively),  the WC grains become smoothly worn.   In the case of "steel cutting grade" cemented carbides, microsections, made normal to the rake face surface, reveal that the WC phase is preferentially worn; the (W,Ti,Ta,Nb)C phase being less severely worn, stands proud of the adjacent WC grains.  The preferential wear of the WC phase is attributed to its higher solid solubility limit in g-Fe (present in the steel chip shear zone during cutting) compared to that of the (W,Ti,Ta, Nb)C phase.

Other tool materials, like high speed steel and ceramics can be worn by this type of mechanism, e.g., when sialon tools are used to cut low alloy and plain carbon steels at cutting speeds above 200 m/min; similarly Al2O3-ZrO2 ceramics exhibit a similar effect when used to cut titanium alloys at cutting speeds above 50 m/min.  TiN and TiC coatings, deposited by PVD or CVD, are also worn in this way when used to cut steels above 100 m/min although other mechanisms like discrete plastic deformation make a significant contribution.   For further details see "Metal Cutting" by E.M. Trent, Butterworths, 3rd Edition, 1992.

Hungary flag Diffúziós kopás

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A term used especially in connection with nitrided steels.  In this xample it refers to the zone of coherent nitride precipitation, residing beneath the compound layer, which constitutes 95 to 99% of the depth of the nitrided "case".   The nitrogen content of the diffusion zone ranges from nearly 20at-% adjacent the compound layer to below 1at-% adjacent the core structure

Hungary flag Diffúziós zóna

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Any technique whereby a coating is formed by immersing a solid in a liquid which subsequently bonds to the solid surface.   The most common types include hot dip aluminising or hot dip galvanising.  The term also refers to coating by immersion in ceramic slip or even polymeric solutions (organic paints). 

Hungary flag Mártással történő bevonás

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A common wear mechanism of PVD and CVD ceramic coatings (TiC, TiN and Al2O3) when used to cut steel at speeds above 100 m/min.   The mechanism increases with increasing cutting speed (temperature) and is the principal rake face wear mechanism of Al2O3 coated cemented carbide tools.   The mechanism culminates in the removal of wear fragements through ductle fracture (see daigram, sequence 1 to 4).  It should be appreciated that coating temperatures often exceed 1100°C when cutting steel; at these temperatures TiC, TiN and Al2O3 behave plastically.       Also see P. A. Dearnley,  R. F. Fowle,  N. M. Corbett and D. Doyle,  Surface Engineering, 1993, 9, 312-318.

Hungary flag Diszkrét képlékeny alakváltozás

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See diamond-like coatings

Hungary flag DLC

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The process of removing residues from washing operations by means of hot or cold air, freon, infra-red radiation or contrifugal action.

Hungary flag szárítás

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A combination of two sequential (and mutually compatible, from the treatment temperature perspective) surface engineering methods to achieve a synergistic surface property design.   At the time of writing, much interest is being shown in extending the application range of thin (≈5µm) ceramic coatings (like TiN and TiC) to low yield strength (≈500-1000M.Pa) substrates by prior strengthening via a thermochemical diffusion treatment.  Feasible duplex treatments include: (i) CVD after carburising, followed by quenching (to permit the g-Fe --> a'-Fe transfomation); (ii) PVD after nitriding.   Note: carburising temperatures ≈ CVD temperatures; PVD temperaturs ≈ nitriding temperatures.  Initial trials have been carried out in two distinct operations.  More recent efforts have focused on enabling each process to be carried out sequentially in the same vessel.

Hungary flag duplex felület technológia


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