Effect of solution heat treatments on superalloys Part 1 - alloy 718

Artikel i vetenskaplig tidskrift, 2012

The hot ductility as measured by Gleeble testing of Alloy 718 at four different solution heat treatments (954 degrees C/15 h, 954 degrees C/1 h, 982 degrees C/1 h and 1050 degrees C/3 h+954 degrees C/1 h) has been investigated. It is concluded that constitutional liquation of NbC assisted by delta phase takes place and deteriorates the ductility. Parameters established by analysing the ductility dependence on temperature indicate a reduced weldability of the material in the coarse grain size state (ASTM 3) while indicating an increased weldability when containing a large amount of delta phase due to a grain boundary pinning effect. The accumulation of trace elements during grain growth at the highest temperature is believed to be the cause for the observed reduced on-cooling ductility.