(Session 8A)Performance of iridium containing nickel base superalloy tool for friction stir welding of Ti-6Al-4V alloy

摘要

The authors have developed a FSW tool made of Ir-containing Ni base superalloy strengthened by precipitation of stable γ' phases, (Ni, Ir)3 -(Al, W) with L12 structure. The purpose of this research is to examine wear behaviour of the Ir-containing Ni base superalloy tool during FSW of Ti-6Al-4V alloy. During FSW of Ti-6Al-4V alloy using the Ir-containing Ni base superalloy tool without water cooling, the probe length hardly changed, although the tool was severely worn on the shoulder and the lateral side of the probe and broken at weld length of 1800 mm. On the other hand, the water cooling could extend the tool life of the Ir-containing Ni base superalloy successfully, although the tool experienced the severe were. In either case, fine γ' phases were observed in the vicinity of the tool surface, suggesting that the tool wear was not attributed to the decrease in strength caused by dissolution of γ' phases. These results implied that the Ir-containing Ni base superalloy tool was mainly damaged by mechanical effects during FSW.