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Comparison of low cycle fatigue characteristics of cast nickel base superalloys Inconel 713 LC a Inconel 792-5A
Petrenec, Martin ; Obrtlík, Karel ; Polák, Jaroslav
Cylindrical specimens of cast polycrystalline nickel base superalloys Inconel 713 LC and Inconel 792-5A were cyclically strained under total strain control at room temperature and at 800 °C. Structural characteristics of both materials are documented. Metallographic observations revealed coarse grains with dendrites, shrinkage pores and carbide inclusions. TEM observation shows differences in the morphology of ordered γ´ precipitates in both materials. Cyclic hardening/softening curves, cyclic stress-strain curves, and fatigue life curves were obtained for both temperatures. The cyclic hardening/softening curves depend both on temperature and plastic strain amplitude. The cyclic stress-strain curves can be approximated by power law. Experimental points of fatigue life curves satisfy the Manson-Coffin and Basquin law. Stress-strain response and fatigue life characteristics are compared at both temperatures and discussed in relation to structural parameters of materials studied.
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Fatigue behaviour of nickel base superalloy Inconel 713LC at high temperature
Juliš, M. ; Obrtlík, Karel ; Podrábský, T. ; Petrenec, Martin
Total strain controlled tests have been performed on cylindrical specimens of Inconel 713 LC polycrystals at 800 °C. Cyclic hardening-softening, cyclic stress-strain and fatigue life curves were obtained. Fracture surface was studied using scanning electron microscopy. High amplitude cycling results in early pronounced hardening followed by softening. Low amplitude cycling is characterized by the stable stress response. Manson-Coffin and Basquin laws can reasonably approximate the fatigue life data. Fatigue crack initiation at casting defects is documented.
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Initial stages of fatigue failure of polycrystalline materials
Man, Jiří ; Petrenec, Martin ; Obrtlík, Karel ; Polák, Jaroslav
Geometry of persistent slip markings (PSMs) formed during cyclic loading of polycrystalline stainless steels and superalloy was studied using atomic force microscopy (AFM) and high-resolution scanning electron microscopy (SEM-FEG). Internal dislocation structure was investigated using transmission electron microscopy (TEM). Persistent slip bands with dislocation structure corresponding to the cyclic strain localization were identified and correlated with PSMs observed on the specimen surface.
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