ON THE INFLUENCE OF COLD WORK ON RESISTIVITY VARIATIONS WITH THERMAL EXPOSURE IN IN-718 NICKEL-BASE SUPERALLOY

Journal Article · Mon Feb 22 00:00:00 EST 2010 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.3362221· OSTI ID:21371009

Madhi, Elhoucine; Nagy, Peter B ^[1]

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1. Department of Aerospace Engineering, University of Cincinnati, Cincinnati, OH 45221 (United States)

In nickel-base superalloys, irreversible electrical conductivity changes occur above a transition temperature where thermally-activated microstructural evolution initiates. The electrical conductivity first decreases above about 450 deg. C then increases above 600 deg. C. However, the presence of plastic deformation results in accelerated microstructure evolution at an earlier transition temperature. It was recently suggested that this well-known phenomenon might explain the notable conductivity difference between the peened near-surface part and the intact part at sufficiently large depth in surface-treated specimens. The influence of cold work on the electrical conductivity change with thermal exposure offers a probable answer to one of the main remaining questions in eddy current residual stress assessment, namely unusually fast and occasionally even non-monotonic decay of the apparent eddy current conductivity (AECC) change that was observed at temperatures as low as 400 deg. C. To validate this explanation, the present study investigates the influence of cold work on low-frequency Alternating Current Potential Drop (ACPD) resistivity variations with thermal exposure. In-situ resistivity monitoring was conducted throughout various heating cycles using the ACPD technique. IN-718 nickel-base superalloy specimens with different levels of cold work were exposed to gradually increasing peak temperatures from 400 deg. C to 800 deg. C. The results indicate that the initial irreversible rise in resistivity is approximately one order of magnitude higher and occurs at about 50 deg. C lower temperature in cold-worked samples of 30% plastic strain than in the intact material.

• OSTI ID: 21371009
• Journal Information: AIP Conference Proceedings, Vol. 1211, Issue 1; Conference: Review of progress in quantitative nondestructive evaluation, Kingston, RI (United States), 26-31 Jul 2009; Other Information: DOI: 10.1063/1.3362221; (c) 2010 American Institute of Physics; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALTERNATING CURRENT
COLD WORKING
EDDY CURRENTS
ELECTRIC CONDUCTIVITY
HEAT RESISTING ALLOYS
HEAT TREATMENTS
MICROSTRUCTURE
NICKEL BASE ALLOYS
PLASTICITY
RESIDUAL STRESSES
STRAINS
SURFACES
TEMPERATURE DEPENDENCE
TRANSITION TEMPERATURE
VARIATIONS
ALLOYS
CURRENTS
ELECTRIC CURRENTS
ELECTRICAL PROPERTIES
FABRICATION
HEAT RESISTANT MATERIALS
MATERIALS
MATERIALS WORKING
MECHANICAL PROPERTIES
NICKEL ALLOYS
PHYSICAL PROPERTIES
STRESSES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT ALLOYS