Weldability of AD730 Nickel alloy
AD730TM is a new nickel base superalloy designed by Aubert&Duval for high temperature applications. It presents very good properties and is cost effective. This type of precipitation-hardened alloy is usually prone to hot cracking and strain age cracking. Thus, it is considered difficult to weld. The aim of this project was to study the weldability of AD730TM using Linear Friction Welding, Electron Beam Welding and Arc Welding with Tungsten Inert Gas.
The material underwent a solution treatment before welding and a post-welding heat treatment after. The later intended to age the material while relieving residual stress.
Firstly, Linear Friction Welding gave really good results on 14.2mm thick samples: homogeneous welds, good microstructure and mechanical properties close to the standard material (ambient and hot tensile, creep tests). Different post welding heat treatment were performed to determine the best way to avoid strain aged cracking.
Secondly, Tungsten Inert Gas welding was performed in both autogenous and with Waspaloy as a filler wire. Fine welds were obtained on 2.5mm and 8mm thick samples respectivelly. Mechanical test on 8mm thick samples presented good tensile properties.
Finally, some preliminary Electron Beam Welding tests were performed on 2.5mm and 27mm thick samples.
Among the three different processes tested, two already presented good results: Linear Friction Welding and Tungsten Inert Gas welding. The third process exhibited few indications of hot cracking but further investigation are on-going. To conclude, the results demonstrated that AD730TM can be welded and gave encouraging mechanical properties.