Abstract: A method of locally repairing parts coated with a thermal barrier including a ceramic outer layer and a metal underlayer of alumina-forming alloy for protecting the substrate against oxidation and for bonding with the ceramic outer layer, includes: defining the zone for repair with a mechanical mask adapted to the shape of the part and the zone for repair; scouring the zone for repair so as to remove the ceramic, the alumina layer, and the damaged portions of the underlayer; supplying materials for repairing the underlayer to the repair zone by subjecting the partially-scoured part to metal deposition by use of an electrical current; and subjecting the part to a heat treatment in order to enable the added metals to diffuse into the remaining underlayer in the repair zone for repair and to enable a surface film of alumina to form. After the underlayer has been reconstituted, the zone for repair is again defined by a mechanical mask and a new ceramic layer is deposited thereon.

Abstract: The invention provides a method of locally repairing parts coated in a thermal barrier constituted by a ceramic outer layer (5) and a metal underlayer (3) of alumina-forming alloy for protecting the substrate (1) against oxidation and for bonding with the ceramic outer layer (5), characterized by the following steps: a) defining the zone (6) for repair with a mechanical mask (8) adapted to the shape of the part (1) and the zone (6) for repair; b) scouring the zone (6) for repair so as to remove from said zone the ceramic, the alumina layer (3b), and the damaged portions of the underlayer (3); c) supplying materials for repairing the underlayer (3) to said zone (6) by subjecting the partially-scoured part to metal deposition by means of electrical current; and d) subjecting the part to heat treatment in order to enable the added metals to diffuse into the remaining underlayer in the zone (6) for repair and to enable a surface film (3b) of alumina to form.

Abstract: The invention relates to a method of overall repair for a part (1) coated in a thermal barrier constituted by a ceramic outer layer (5) and a metal underlayer (3) of alumina-forming alloy, the method being characterized by the following steps: a) subjecting the metal part (1) for repair to thermochemical treatment under fluorine-containing halogen gas for a length of time that is sufficient to eliminate the aluminum contained in the underlayer (3) and any oxides and sulfur compounds that might be present at the surface of the part (1) and in cracks (6), thereby causing the ceramic layer (5) to be removed and causing the part (1) to be passivated; b) restoring mechanical integrity to the part (1) by methods of repairing any cracks (6) by adding material; c) enriching the surface of the part in aluminum, if necessary; and d) depositing a new layer (5) of ceramic. The invention is particularly applicable to the blades of the high pressure turbine of a turbomachine.

Abstract: At least one gaseous precursor of the deposit to be made comprising an aluminum compound is brought by means of a carrier gas into contact with the surfaces of the part which is placed inside an enclosure. The carrier gas is selected from helium and argon and the pressure inside the enclosure is selected in such a manner that the mean free path of the carrier gas molecules is at least twice as long as that of argon molecules under atmospheric pressure. The method is suitable in particular for aluminizing gas turbine blades that have internal holes and cavities.

Abstract: At least one gaseous precursor of the deposit to be made and comprising an aluminum compound is brought with the help of a carrier gas into contact with the surfaces of parts placed in an enclosure. The carrier gas is selected from helium and argon, and the pressure inside the enclosure is selected in such a manner that the mean free path of the carrier gas molecules is at lest twice as long as that of argon molecules under atmospheric pressure. The method is particularly suitable for aluminizing a low pressure turbine ring sector of a turbomachine, the sector being provided with an abradable honeycomb coating.

Abstract: A process for producing a coating for protecting superalloy articles against high temperature oxidation and hot corrosion comprises forming, on the surface of the article, a first deposit of an agglomerated powdered alloy containing at least chromium, aluminum and an active element, and filling the open pores of the powder deposit by a second, electrolytically applied, deposit of a precious platinum group metal. An appropriate thermal treatment is then carried out to effect interdiffusion between the powder based deposit and the electrolytic deposit and produce a coating including chromium, an active element such as yttrium, and a precious platinum group metal throughout its thickness.

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: In a process for the simultaneous deposition of a protective coating, e.g. an aluminuim based coating, on internal and external surfaces of heat-resistant alloy parts, the parts are placed in a box containing a donor material, preferably in the form of granules, comprising the metal to be deposited, and an activator separate from the donor and comprising at least an anhydrous powder of chromium fluoride CrF.sub.3 to provide a source of fluorine. The box is heated to a temperature above 1000.degree. C. and a controlled flow of a carrier gas, reducing or neutral, is introduced into the box so as to establish a circulation of gases in the box whereby fluorinated vapors from thermal decomposition of the CrF.sub.3 activator contact the donor to form a volatile fluoride of the metal to be deposited, and the volatile vapor is carried into contact with the external and internal surfaces of the parts to be coated to deposit the coating thereon.

Abstract: In a process for the simultaneous deposition of a protective coating, e.g. an aluminium based coating, on internal and external surfaces of heat-resistant alloy parts, the parts are placed in a box containing a donor material, preferably in the form of granules, comprising the metal to be deposited, and an activator separate from the donor and comprising at least an anhydrous powder of chromium fluoride CrF.sub.3 to provide a source of fluorine. The box is heated to a temperature above 1000.degree. C. and a controlled flow of a carrier gas, reducing or neutral, is introduced into the box so as to establish a circulation of gases in the box whereby fluorinated vapors from thermal decomposition of the CrF.sub.3 activator contact the donor to form a volatile fluoride of the metal to be deposited, and the volatile vapor is carried into contact with the external and internal surfaces of the parts to be coated to deposit the coating thereon.

Abstract: The instant invention describes a method of repairing heat-resistant alloy parts which have been cracked or otherwise damaged due to exposure of combustion gases from a turbojet engine. The method includes chemically cleaning the surface of the part to remove the layer of contaminants and subjecting the part to a thermochemical treatment to thoroughly clean the cracks and other narrow, damaged areas. A diffusion brazing process is then utilized to fill the cracks or damaged areas.