Abstract: The method according to the invention comprises the following operations: a) prepare a substrated formed of the said intermetallic alloy; b) deposit a coating of gold on the surface to be protected of the substrate; and c) subject the substrate thus equipped with the gold coating to annealing in controlled conditions in order to bring about limited diffusion of the gold into the surface to be protected. The invention is applicable in particular to parts of gas turbines, e.g. parts of aircraft engines.

Abstract: The invention relates to a method of brazing a Ti—Al alloy. According to the invention, a layer of nickel (2) is disposed between a part (1) which is made from titanium aluminide and a brazing sheet (3), such as to enable: the aforementioned part (1) to be brazed to another metallic material (4) without the aluminium diffusing from one to the other; and a stable link with good mechanical strength to be produced. The invention can be used for the assembly of aircraft engine parts which are made from titanium aluminide and nickel-based superalloy.

Abstract: Hollow metal spheres are heated in a high vacuum in the presence of an organic substance, at a temperature at least equal to the melting point of a eutectic between carbon and the metallic constituents of the said spheres.

Abstract: In order to protect a monocrystalline superalloy rich in rhenium against corrosion whilst avoiding the formation of progressive secondary reaction zones, a layer (3) formed of tungsten and cobalt is deposited on its surface before aluminisation treatment.

Abstract: The invention concerns a method wherein the substrate (5) to be coated is immersed in an autocatalytic chemical deposit bath (4), for example nickel, contained in a stainless steel vessel (1) and wherein can be optionally mixed a suspended MCrAlY alloy, so as to form a metal deposit (nickel) wherein are optionally included powder particles. The invention is characterised in that, to provide a prolonged operation of the bath, it consists in measuring with a voltmeter (8) the difference of potential between the substrate (5) and a reference electrode (6) immersed in the bath (4), and in imposing between the substrate (5) and the vessel (1) an electric current produced by a generator (10), said current being adjusted by a regulator (11) so as to maintain said potential difference at a selected value.

Abstract: The invention concerns a method wherein the substrate (5) to be coated is immersed in an autocatalytic chemical deposit bath (4), for example nickel, contained in a stainless steel vessel (1) and wherein can be optionally mixed a suspended MCrAlY alloy, so as to form a metal deposit (nickel) wherein are optionally included powder particles. The invention is characterised in that, to provide a prolonged operation of the bath, it consists in measuring with a voltmeter (8) the difference of potential between the substrate (5) and a reference electrode (6) immersed in the bath (4), and in imposing between the substrate (5) and the vessel (1) an electric current produced by a generator (10), said current being adjusted by a regulator (11) so as to maintain said potential difference at a selected value.

Abstract: This relates to an improvement to the process of aluminization or activated cementation in which a donor cement containing the aluminium is attacked at high temperature and in a neutral or reducing atmosphere by a gaseous ammonium halide to form a gaseous aluminium halide which decomposes on contact with a nickel-based substrate depositing aluminium metal thereon.

Abstract: The invention concerns a method comprising a step which consists in producing, on a precursor alloy powder containing at least the elements Cr, Al and Y, using a chemical or electrolytic deposition bath, a deposition containing at least a modifying element such as platinum, palladium, ruthenium or rhenium. The modifying element enhances the capacity of the coating to form from phase &bgr;, by exposure to oxygen at high temperature, an adhesive alumina surface barrier. The invention is useful for protecting against corrosion and oxidation at high temperatures aviation turbine blades.

Abstract: A thermal barrier coating for a superalloy part used, in particular, in turbomachines comprises a ceramic coating and a sub-layer interposed between the superalloy substrate and the ceramic coating, the sub-layer being composed of a nickel and/or cobalt aluminide containing at least one platinum-like metal and at least one metal for promoting the formation of a layer of oxide constituted by the alpha-allotropic variety of alumina.

Abstract: The sealing composition contains powders composed, by weight, of 70 to 90% of aluminium, 5 to 25% of silicon, 0 to 5% of silica and 0.1 to 5% of moderating metal, which are dispersed in a vehicle comprising an organic binder dissolved in a solvent and a mineral binder.It is applied to the faces to be assembled of a ceramic part and of a refractory alloy or superalloy part and the whole is heated in order to eliminate said vehicle and form between the two parts a layer of mullite syncrystallized with the ceramic.

Abstract: A surface layer of a material containing carbon and/or a carbide is produced on the outer surface of a solid carbon-based substrate (1) by selective application of material, said surface layer adhering strongly to the substrate, having a high specific surface area and having open pores (5) of a depth of at least 1 nm, and a metal material having a strong affinity for carbon, comprising at least one metal chosen from cerium, cobalt, chromium, iron, hafnium, iridium, osmium, palladium, platinum, rhodium, ruthenium, lanthanum, manganese, molybdenum, nickel, silicon, tantalum, thorium, titanium, uranium and tungsten, is deposited on said surface layer, substantially filling said pores.The metal deposit (8) may be rectified and polished without peeling off, in order to produce a mirror of low inertia.

Abstract: The bath contains an oxalate of the metal or of each of the metals to be deposited and hydrazine as a reducing agent, together with ethylenediamine as a complexing agent and at least one stabilizing agent, said bath being highly basic and having an autocatalytic effect.

Abstract: A method including aluminization treatment preceded by a palladium predeposition treatment, the palladium being associated with at least one barrier metal selected from nickel, cobalt, and chromium, thereby avoiding hydrogen occlusion.

Abstract: A nickel and/or cobalt chemical plating bath comprises: a salt of the metal(s) to be deposited; one or more complexing agents of said metal(s), a reducing agent based on boron or phosphorous; and a stabilizing agent. To avoid including sources of corrosion and/or toxic substances in the plating, the stabilizing agent comprises a water soluble organic compound which possesses a readily accessible electron pair, and which does not include any metal or metalloid from group IIIa (other than boron or aluminum), IVa (other than carbon), Va (other than nitrogen or phosphorous), VIa (other than oxygen), or VIIa (other than fluorine or chlorine).