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

摘要

A method for providing an integral extension on an article comprises 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 has a superalloy composition and a directionally oriented crystal structure. A mandrel (200) is attached to the extension bonding surface. The mandrel has 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. The mandrel also has an alloy composition that is compatible with the superalloy composition. A ceramic mould (300) is formed over the outer surface of the mandrel and a portion of the outer surface of the extension end. The mould has a cavity with a shape that is defined by the mandrel and defines the shape of the integral extension. The mandrel is melted under controlled conditions by application of an external heating means, the article, mandrel and mould being oriented either prior to or during the melting so that the molten mandrel contacts the extension bonding surface, for a time sufficient to permit the extension bonding surface to be heated by and interact with the molten mandrel as a microstructure growth seed. The extension end (700) is cooled under controlled thermal conditions so as to cause the molten mandrel to solidify on the growth seed, at an interface between them that moves from the extension bonding surface into the molten mandrel, as an integral extension that conforms to the shape of the mould cavity and has a microstructure that is compatible with the microstructure of the extension end. The controlled thermal conditions comprise 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 is a second method for providing an integral extension on an article.