Deposition Technologies for High Strength Ni Alloys
A. Wisbey, P. Holdway, H. S. Ubhi, QinetiQ, Farnborough, United Kingdom; J. Segal, I. Pashby, Nottingham University, Nottingham, United Kingdom; S. Jones, Rolls-Royce, Derby, United Kingdom; J. Allen, Medtronic Vascular, Santa Rosa, CA
Reducing the cost of manufacturing high performance aero-engine components is crucial for the introduction of new high fuel efficiency engine technology and designs. One particular area is that of large wrought nickel alloy components, which have been traditionally produced from oversize wrought products and then machined to final size, with significant wastage. An alternative approach may be to employ conventional welding to assemble pre-formed parts, however, many of the higher strength wrought nickel alloys are considered unweldable. The new additive manufacturing routes now available may offer a solution to some or all of these problems.
In the work reported here the high strength nickel alloy, Waspaloy, has been evaluated using various deposition technologies. These have included four different heat sources – GTAW, diode laser, Nd-YAG laser and electron beam, and both wire and powder feed. Simple wall type deposits have been manufactured using these techniques and the deposits have then been examined microstructurally, along with their tensile performance. Some investigation of the role of deposition parameters has been evaluated, especially for the GTAW and diode laser heat source techniques.
Large columnar grains were found with most of the processes used, however, the GTAW system gave the largest grain size, with the Nd-YAG the smallest. Some anisotropy in the tensile properties was found with all of the deposition processes. The work reported here has shown that the deposition technology selected is very dependent on the geometry of the target component and the level of subsequent machining tolerable.
Summary: Reducing the cost of manufacturing high performance aero-engine components is crucial for the introduction of new high fuel efficiency engine technology and designs. Large wrought nickel alloy components are conventionally produced significantly oversize, to permit overall machining, with the attendant high scrap level. An alternative approach may be the use of the developing additive manufacturing techniques to assemble or produce closer to near net shape components. In this paper four different manufacturing techniques have been examined for use with a high strength nickel alloy, which is often considered unweldable conventionally. The microstructure developed, along with the tensile behaviour are presented.