Effect of hot corrosion on low cycle fatigue behavior of superalloy IN718

Low cycle fatigue behavior of the superalloy IN718 was studied with Type-A (Na2SO4 + NaCl) and Type-B (Na2SO4 + NaCl + V2O5) salt coatings, at 650 °C in total strain controlled mode. Fatigue life of the salt coated specimens was found to be drastically reduced at all the total strain amplitudes. In general there was cyclic softening both in the bare as well as salt coated specimens. Variation of fatigue life with plastic strain amplitude followed Coffin-Manson relationship. Reduction in fatigue life from salt coating was found to be associated with early crack initiation from the roots of corrosion pits on the surface and faster crack propagation.