Melting and Refining of Superalloys and Titanium Alloys.

Abstract

The processes used for the manufacture of both superalloys and titanium for the aerospace industry i.e. vacuum induction melting, vacuum arc melting and electroslag remelting, are to be considered as mature technologies. They have been developed over many years in regard to both the equipment used and the process techniques. They have been found to have advantages and have been manifestly successful in producing high quality material as attested to by the impressive reliability of turbines in service. However, in the present progress of turbine manufacture we have arrived at a position where the operational improvements in engine performance require alloy components of even higher reliability–beyond that which can be guaranteed by the present processes, for reasons which are discussed below. We are hence at an interesting stage in the development of the melting processes where we have little potential left in the present techniques and must therefore introduce the next stage in the technical development. The discussion below outlines the rationale for the choice of this type of new process, based on both absolute quality and also on quality assurance through process control. It is concluded that for both titanium alloys and superalloys, electron-beam melting can provide the incremental improvement which we need, as is being presently demonstrated by the industrial introduction of electron beam technology.