Strength and Fracture of a Nickel-Base Superalloy Subjected to Different Waveforms of Loadings in Hot Corrosion Environment

Yoshiba Masayuki, Miyagawa Ohmi, Hamanaka Tatsuya

doi:10.3323/jcorr1974.39.3_132

In order to clarify an environmental effect of hot corrosion on the strength properties and fracture behavior of a nickel-base superalloy subjected to different waveforms of loadings, the fatigue, creep and three kinds of combined creep-fatigue tests were performed at 800°C of Inconel 751 specimens coated with the synthetic salt mixture composed of 90% Na₂SO₄-10% NaCl. Hot corrosive environment was found to induce serious degradation of the rupture life depending on the loading conditions. In particular, the combined creep-fatigue tests resulted in the minimized rupture life in the corrosive environment, while a monotonic creep caused the most prolonged life. A fatigue component in the loading was also found responsible for the corrosion-induced premature fracture together with a creep component, although in air it plays little important role in the fracture behavior. Hot corrosive environment was also characterized by the intergranular fracture in a brittle manner regardless of the loading conditions, which is directly caused by the stress-enhanced intergranular penetration of sulfides, oxides and/or chlorides. The possible effects of the fatigue and creep components on such a predominant intergranular attack behavior were discussed.

Strength and Fracture of a Nickel-Base Superalloy Subjected to Different Waveforms of Loadings in Hot Corrosion Environment

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