Method for forming an article extension by melting of an alloy preform in a ceramic mold

摘要

A method for providing an integral extension on an article comprising the steps of: (a) selecting an article (100) comprising an extension end , an extension bonding surface and an outer surface defined by the cross sectional shape. The extension end also having a superalloy composition and a directionally oriented crystal structure. (b) attaching a mandrel (200) to the extension bonding surface, the mandrel having a cross sectional shape that is compatible with the cross sectional shape of the extension end and an outer surface that communicates with the outer surface of the extension end. (c) forming a ceramic mould (300) over the outer surface of the mandrel and a portion of the outer surface of the extension end. The mould having a cavity with a shape that is defined by the mandrel and defines the shape of the integral extension. (d) removing the mandrel (180). (e) inserting an alloy preform (500) having an alloy composition that is compatible with the superalloy composition into the mould cavity and melting the preform under controlled conditions by application of external heating. The article, alloy and mould being oriented either prior to or during the melting so that the molten alloy contacts the extension bonding surface for a time sufficient to permit the extension bonding surface to be heated by and interact with the molten alloy as a microstructure growth seed. (f) cooling the extension end (700) under controlled thermal conditions so as to cause the molten alloy to solidify on the growth seed at an interface between them that moves from the extension bonding surface into the molten alloy, as an integral extension that conforms to the shape of the mould cavity and has a directionally oriented microstructure that is compatible with the microstructure and is an epitaxial extension of the extension end. The controlled thermal conditions comprising maintaining a temperature gradient within the article such that the temperature is highest at the interface and decreases within the article as a function of increasing distance from the interface. Also claimed are a method in which the article is an airfoil and a method in which the ceramic mould is preformed.