Strain ratio effect on microstructural evolution during low cycle fatigue exploitation of nickel base superalloy IN 740H

Kumar, C and Jena, P S M and Singh, R K and Harmain, G A and Sahu, J K (2021) Strain ratio effect on microstructural evolution during low cycle fatigue exploitation of nickel base superalloy IN 740H. International Journal of Pressure Vessels and Piping, 194 Part B .

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Abstract

Strain ratio (Re) is varied during isothermal strain-controlled fatigue tests of nickel-base superalloy IN740H at 760 degrees C; R-epsilon = -1, 0, 0.5. Unlike most alloys, highest fatigue life is observed under R-epsilon = 0 test condition compare to R-epsilon = -0.5 and -1. From extensive electron microscopy, i.e. energy-filtered TEM (EF-TEM), WDS and EDS studies, it is confirmed that the creep effect due to tensile mean stress under R-epsilon = 0 condition was offset due to segregation of Nb at dislocation and formation of Nb(CN) at grain boundaries, which proved to be fatigue strengthening. Debonding of Nb(CN) and. matrix provided preferential fatigue crack initiation sites and resulted in lowering the fatigue life for R-epsilon = 0.5 test condition.

Item Type:Article
Official URL/DOI:https://doi.org/10.1016/j.ijpvp.2021.104551
Uncontrolled Keywords:Low-cycle fatigue; fatigue life; dislocation; Ni-base superalloy; mean stress; behavior
Divisions:Material Science and Technology
ID Code:8443
Deposited By:Dr Mita Tarafder
Deposited On:01 Nov 2021 12:18
Last Modified:01 Nov 2021 12:18
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