Interaction of hot corrosion and creep in Alloy 617

• The salt-deposit melts at the elevated temperature and penetrates into the creep cracks.
• Hot corrosion leads to the formation of intergranular voids and oxides, thereby the earlier start of tertiary creep.
• Hot corrosion promotes the direct-decohesion of grain boundaries.
• The damage by hot corrosion and creep accumulates and decreases the fracture ductility and creep life.

In the present work, Alloy 617 was subjected to creep in the absence and presence of hot corrosion (i.e. with and without a deposit of sodium salts) under different load magnitudes at 850 °C. Additionally, a sample of the alloy was exposed to hot corrosion without applying creep. The results revealed that the creep behavior of Alloy 617 was substantially affected by hot corrosion which accelerated creep and led to a considerable reduction in the fracture ductility and creep life of the alloy. Microscopic examinations demonstrated that the strain-to-rupture decreased due mainly to the damage accumulation during tertiary creep. Various mechanisms of hot-corrosion/creep interaction were discussed that highlighted the destructive role of M23C6 precipitates in the interaction. It was explained that hot corrosion contributed to the reduction of grain-boundary cohesive-strength followed by extensive cavitation at transvers grain boundaries.