From research to cost effective directional solidification and single crystal production - an integrated approach - part C

Abstract

The integrated approach to automated production technologies has required work in three broad areas. 1. Process Development 2. Material Development 3. Quality Assurance It necessitates bringing together a multidisciplined task force with specialists in metallurgy, ceramics, a non-destructive testing, x-ray diffraction, plant and equipment design, control systems and manufacturing engineering. The result of these programmes has been to develop and prove an automated technology for the production of high quality cost effective Directionally Solidified (DS) and Single Crystal (SC) Castings and in the latter case has led to the use of the seeding technique which, though technically more difficult, allows greater flexibility. As a result of carefully optimised furnace design, enhanced thermal gradients are achieved resulting in improved casting quality coupled with a greater flexibility for the alloy developer. This has led to the development of a series of three alloys to meet specific turbine applications. The need to provide rapid, accurate and audited measurement of single crystal orientation has been met by the development of SCORPIO which is a real time rapid orientation measurement system for the production environment. In the continual search to raise the quality and reliability of the product much development work has been carried out to match process capability with component design intent leading to development of new methods, processes and production control techniques for dimensional control, cleanliness, solution treatment and orientation control. The enabling factor has been the deliberate bringing together of the component design team, the manufacturing engineers and metallurgists into one team for the earliest design stages right through to the production mature process. The success of the integrated approach is best judged by the precise measurement of labour times and material costs for the identical blade made on production by equiaxed, DS and SC casting process and by the complexity and quality of the casting that can be achieved.