Inner and outer surfaces of structural components are aluminized by an aluminum gas diffusion process. For this purpose a gas mixture of a halogenous gas, aluminum monohalide gas, hydrogen, and negligible proportions of aluminum trihalide gas is caused to flow over the outer and inner surfaces of the component to be coated. The process is performed in a vessel in which at least two different temperature zones are maintained for keeping one or more aluminum sources at a higher temperature than the component to be coated. Especially gas turbine engine blades are protected against oxidation and corrosion by the so formed aluminum diffusion coatings on outer and inner surfaces of the blades.
In a gas phase coating process for coating turbines blades or housing parts, one or more workpieces to be coated are arranged in a container that is heated. Propellant is supplied to the container via a propellant pipe. A donor substance is arranged at the floor of the container together with an activator and forms a coating gas that is circulated pulse-like in the interior of the container by means for circulation, for example, a Venturi nozzle from which the propellant emerges.
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.According to the invention the aluminium halide is at least partly replaced by a zirconium halide leading to the inclusion of zirconium in the deposit.Improvement in the protection of the hot parts of aircraft engines made of nickel-based superalloy.No figure is to be published.
In a method for coating workpieces with a coating material by a gas phase diffusion coating process, the coating material is conveyed in the form of a metal halide compound from a coating material source (9A, 9B, 9C) to the workpiece (7) by means of a metal halide gas circulation flow (F). The gas circulation flow (F) is physically induced due to convection by establishing a temperature gradient between the workpiece (7) and the coating material source (9A, 9B, 9C), and is reinforced by the chemical reactions taking place. An apparatus for carrying out a gas phase diffusion process includes a reaction vessel (3) enclosing a reaction chamber (1) in which the workpiece (7) is arranged. The apparatus further includes a metal halide generator (9A, 9B, 9C) arranged in the reaction chamber (1), and a heater (5) as well as a cooling device (6) and a thermal conduction arrangement (8) for establishing a temperature gradient between the workpiece (7) and the metal halide generator (9A, 9B, 9C). The method and apparatus produce a diffusion coating having a uniform thickness and a high quality smooth surface, even on large workpiece surfaces.
In a method for coating workpieces with a coating material by a gas phase diffusion coating process, the coating material is conveyed in the form of a metal halide compound from a coating material source (9A, 9B, 9C) to the workpiece (7) by means of a metal halide gas circulation flow (F). The gas circulation flow (F) is physically induced due to convection by establishing a temperature gradient between the workpiece (7) and the coating material source (9A, 9B, 9C), and is reinforced by the chemical reactions taking place. An apparatus for carrying out a gas phase diffusion process includes a reaction vessel (3) enclosing a reaction chamber (1) in which the workpiece (7) is arranged. The apparatus further includes a metal halide generator (9A, 9B, 9C) arranged in the reaction chamber (1), and a heater (5) as well as a cooling device (6) and a thermal conduction arrangement (8) for establishing a temperature gradient between the workpiece (7) and the metal halide generator (9A, 9B, 9C). The method and apparatus produce a diffusion coating having a uniform thickness and a high quality smooth surface, even on large workpiece surfaces.
A gas distributor suitable for introducing a carrier gas at the top of a coating container used to provide a metallic coating on articles. The gas distributor includes a gas inlet and a gas outlet head in communication with the gas inlet for receiving a flow of gas from the gas inlet. A plurality of gas outlets through which the gas flow exits as a gas stream are spaced along the peripheral surface of the gas outlet head. A plurality of gas deflectors, each proximate to one of the gas outlets, at least initially direct the gas stream exiting the gas outlet in at least a generally centripetal path. This gas distributor can be used in vapor coating apparatus having a coating container, at least one holder for each article to be coated positioned within the coating container and below the gas outlet head of the gas distributor and at least one holder for the source of the metallic coating positioned within the coating container and below the gas outlet head of the gas distributor. A method is also provided for introducing the carrier gas as a plurality of carrier gas streams proximate the top of the coating container so that each carrier gas stream flows at least initially in at least a generally centripetal path, as well as a method for coating the articles with a metallic coating in the coating container.
