Nickel-containing superalloy laser weld qualities and properties

Hot section jet engine and elevated temperature corrosion-resistant applications can both require high integrity welding of nickel-containing superalloy components, both in original fabrication and subsequent repair operations. However, it is recognized that there can be a number of difficulties when welding these alloys, including the introduction of cracks, pores, distortion, and/or the degradation of mechanical properties. Laser welding, being a low heat input process, has potential for low distortion fabrication. However, concerns remain around the weld qualities that can be achieved in these materials [Khan et al., “Meeting weld quality criteria when laser welding Ni-based alloy 718,” in ICALEO, Anaheim, USA (2012), Paper No. 1707], and the effect laser welding could have on material properties. In this work, TWI and NLR have examined the development and application of fiber laser welding for a number of superalloys, of different grades and thicknesses. The weld qualities and microstructures were evaluated (e.g., using X-ray radiography, metallographic sectioning, and microscopic examination). Selected static and dynamic mechanical properties were also measured, both at room temperature and at elevated temperatures, more representative of service conditions. In this way, the relative qualities, tensile strengths, ductility, and low cycle fatigue behaviors of a range of different laser welds have been compared.