Centre Stephanois De Recherches Mecaniques Hydromecanique Et Frottement

Tecmachine

Centre Stephanois De Recherches Mecaniques Hydromecaniques Et Frottement

Centre Stephanois De Recherches Mecanmiques Hydromecanique Et Frottement

H.e.f.

Jean-Paul Terrat

Philippe Maurin-Perrier

Christophe Heau

Antoine Gaucher

Andre Aubert

Jean-Marc Poirson

Pascal Fort

Michel Martin

Hocine Hadj-Rabah

Fr&eacute;d&eacute;ric Faverjon

Daniel Viviani

Stéphane Chomer

Janick Moreau

Jacques Chevallier

A device () for amplifying the current of an abnormal electrical discharge, characterized in that it comprises an electrode which is positively polarized () and associated with a magnetic circuit () producing a magnetic field () which is uniformly divergent, whereby the intensity on the surface of the electrode is more than approximately 6.10Tesla, the electrode being positioned in the region where the magnetic field is at its most intense.

Device for amplifying the current of an abnormal electrical discharge and system for using an abnormal electrical discharge comprising one such device

A method for obtaining a ferrous alloy part that supports a very high seizure load with very low dispersion includes steps of covering the part with an iron sulphide coating having an appropriate thickness and Fe/S ratio, where the coating is selected from among those with surfaces having a fractal dimension that is at least equal to 2.6.

Method for treating ferrous alloy parts in order to improve the rubbing properties thereof without causing hardness loss or deformation

The metal alloy based on aluminium and titanium includes an aluminium content between 80 and 90 atomic percent and a titanium content between 10 and 20 atomic percent. The alloy is microcrystalline and outside thermodynamic equilibrium, the alloy is thereby resistant to oxidation and corrosion and has at the same time remarkable adhesion to polymer materials. The metal alloy can be in the form of a reflecting coating of a thickness ranging between 0.01 and 3 &mgr;m, covered with a protective film of a polymer material. A mirror having specular reflectivity not less than about 65%, good resistance to corrosion and oxidation includes a substrate of a polymer material supporting the reflecting coating.

Aluminum-titanium alloy with high specular reflectivity, reflecting coatings comprising same and mirrors and parts comprising said coating

In a nitriding method intended to confer upon ferrous metal parts, in addon to surface properties resulting directly from nitriding, corrosion resistance comparable to that obtained when the nitriding treatment is followed by an oxidizing treatment, in particular in a salt bath, the parts are treated by immersion for an appropriate time in a molten salt bath containing in the known manner essentially alkali metal carbonates and cyanates and a small quantity of a sulfur-containing substance. The parts are held at a positive potential relative to a counter-electrode in contact with the bath so that a high current flows through the bath from the parts to the counter-electrode and the concentration of cyanides formed by secondary reaction is kept below 6%. It is preferable to use a constant average current; the typical current densities are from 300 amperes to 800 amperes per m.sup.2, the typical temperature ranges are from 450.degree. C. to 650.degree. C. and the typical treatment times are from 10 minutes to 150 minutes.

Method of nitriding ferrous metal parts having improved corrosion

A salt bath composition is adapted to form a layer of magnetite Fe.sub.3 O.sub.4 on the surface of ferrous metal parts, including nitrided ferrous metal parts, to protect the underlying iron against corrosion. This layer is impermeable and of good crystalline order, as indicated by a deep black color and a corrosion potential greater than 1 000 mV. The composition includes at least nitrate anions and sodium and lithium cations, the latter in a proportion by weight relative to the bath between 0.1% and 5%, preferably between 0.5% and 1.75%. Preferred compositions contain sodium, potassium and lithium cations and nitrate, carbonate and hydroxyl anions, within the following percentage ranges:

Salt bath composition based on alkali nitrates for oxidizing ferrous

Coating for conferring good friction properties upon a substrate and comprising a non-equilibrium alloy of chromium and nitrogen. The alloy comprises, per one hundred atoms, from 87 to 68 atoms of chromium and from 13 to 32 atoms of nitrogen and two phases, a cubic microcrystalline chromium phase containing included nitrogen and a quadratic chromium nitride phase with a stoichiometric deficient nitrogen content relative to the Cr.sub.2 N nitride. The ratio of the quadratic nitride lattice parameters is between 1.02 and 1.5. This quadratic nitride was previously unknown and probably can exist only in association with chromium. It resists wear up to five times better than known single-phase chromium-nitrogen alloys and is free of the inherent fragility of two-phase alloys containing hexagonal Cr.sub.2 N nitride. The coatings are obtained by magnetron cathode sputtering of chromium with a nitrogen partial presure in a rare gas atmosphere between a maximum and a minimum determined experimentally.

Chromium-nitrogen alloy surface coating composition

By cathode sputtering in a reactive environment, a coating of a solid solon of chromium and an element such as nitrogen, carbon, phosphorus, boron or silicon is deposited. The content of the above element is higher than the saturation limit of the solid solution in chromium. It ranges between T.sub.m =0.2% and T.sub.M =3% by weight for carbon and between T.sub.m =0.04% and T.sub.M =3.5% by weight for nitrogen.

Chromium coating with high hardness capable of resisting wear, strain

An antifriction alloy containing iron, molybdenum and sulphur, and having a low coefficient of friction, even in the dry state, is disclosed. The alloy contains 8.0-26.6% iron, 41.0-62.5% molybdenum and 23.3-40.5% sulphur. The alloy may comprise a matrix of Fe.sub.x Mo.sub.3+y S.sub.4, where x and y are less than 1. (e.g. FeMo.sub.4 S.sub.5) in which is dispersed FeMo.sub.2 S.sub.4 and/or the .epsilon. phase of the Fe/Mo/S equilibrium diagram. The alloy reacts with a material against which it rubs, to form the sulphide of that material on the rubbed surface. The alloy may be made by chemical reaction, fusion, vacuum deposition, or powder metallurgy. It can be used alone, or as a surface layer on, or inclusion in, another material, or it can be dispersed as a powder in a lubricant.

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Saint-Etienne, France

Jean-Paul Terrat