Product Code: ICA12_1707

Meeting Weld Quality Criteria When Laser Welding Ni-Based Alloy 718
Authors:
Ali Khan, TWI Ltd; Cambridge Great Britain
Paul Hilton, TWI Ltd; Cambridge Great Britain
Jon Blackburn, TWI Ltd; Cambridge Great Britain
Chris Allen, TWI Ltd; Cambridge Great Britain
Presented at ICALEO 2012

Significant numbers of aero-engine parts are manufactured with Ni-based superalloys because of their excellent heat and corrosion resistant properties. Weld imperfections, such as those associated with bead geometry, sub-surface porosity and liquation cracking are of concern, given the high-performance service requirements of fabricated Ni-based components in the aerospace sector. Weld quality criteria are stipulated in AWS D17.1:2001, a standard for the fusion welding of aerospace components and it is known that more stringent criteria, usually company-specific to various aero-engine manufacturers, also exist. In this paper, a high beam quality 1 m laser source was used to determine the effects of different process parameters on the quality of welds made in 3 and 5mm thickness Alloy 718. The principal focus of the project was to compare the results obtained for bead geometry, sub-surface porosity and liquation cracking to Class A of AWS D17.1:2001 and a generic, more stringent company-specific standard.
A general summary of the results shows AWS D17.1:2001 geometry and porosity criteria can be met over a fairly wide range of speed and power with this type of laser. This window is greatly reduced if liquation crack free welds are required. If, in addition, it is also required to meet the more stringent company-specific criteria for porosity and geometry, the window is even further reduced.