Welding of superalloys

Superalloys are metals mainly consisting of nickel, alloyed with a lot of other metallic elements. These superalloys are used for example in aerospace engines, for parts becoming extremely hot. Other metals, like steel, cannot be used at these temperatures, since they loose their strength. Superalloys are used in both cast and forged conditions and as sheets.

Welding of superalloys is very difficult. Special welding processes as GTAW, laser and electron beam welding are use. One problem that may arise is cracking in aand around the weld. One of the research projects at University West is dealing with a special kind of cracks called "strain-age cracking". These often appear in conjunction with heat treatment after welding, but may also occur in connection to weld repair of cast material. In the project the mechanism behind these cracks and how they can be avoided will be studied. The problem is very complex and both experimental investigations as well as modelling of the welds will be made. A cooperation with University of Cambridge in UK is planned. 

In another project the effect of heat treatment of cast material (so called homogenisation) on the properties of welded joints will be studied. There exists a number of different recommendations for how the homogenisation shall be performed, but the knowledge about how these recommendations in combination with different welding methods affect the welded joint is limited. The aim of the project is to achieve a fundamental understanding how the microstructure after homogenisation affects the weldability and come up with recommendations about how the homogenisation shall be performed to achieve optimised properties.