Applications of superplastic forming and diffusion bonding to hollow engine blades

摘要

The practical application of technology based on superplastic forming combinedwith diffusion bonding (SPFIDB) to advanced aircraftengine blade manufacturing is investigated in this paper.Four-sheet hollow engine blades, a Ti-6Al-4Vsandwich structure, have been fabricated through theSPF/DB process after determining the designdimensions and deformation procedures. Some noveldesigns and special auxiliary techniques have beendeveloped to facilitate the superplastic SPF/DBprocess. The finished blades can meet the property andprofile demands, particularly in the boundary region(the leading and the trailing). The effects of themicrostructure on the SPF/DB process were discussed.Slight grain growth was observed after the thermalexposure. Tensile tests show a strength reduction of30percent from the as-received sheets to the formedsheets. The microstructures at the interfaces indicatethat a bonding ratio of 100percent can be reached inmost bonding areas. Low bonding ratios in someregions such as cell comers and triple angles wereunavoidable. The bonds present in the blade structurescan be divided into four types, based on their formationquality characteristics. The distribution in thicknessand bonding ratio within a formed cell wereinvestigated, revealing two deformation localizationzones and a poor-bonding area. Further processing ofthe formed structures involves electric spark machining and surface polishing.