Microstructure-Based Lifetime Assessment of Austenitic Steel AISI 347 in View of Fatigue, Environmental Conditions and NDT

Abstract

The assessment of metallic materials used in power plants’ piping represents a big challenge due to the thermal transients and the environmental conditions to which they are exposed. At present, a lack of information related to degradation mechanisms in structures and materials is covered by safety factors in its design, and in some cases, the replacement of components is prescribed after a determined period of time without knowledge of the true degree of degradation. In the collaborative project “Microstructure-based assessment of maximum service life of nuclear materials and components exposed to corrosion and fatigue (MibaLeb)”, a methodology for the assessment of materials’ degradation is being developed, which combines the use of NDT techniques for materials characterization, an optimized fatigue lifetime analysis using short time evaluation procedures (STEPs) and numerical simulations. In this investigation, the AISI 347 (X6CrNiNb18-10) is being analyzed at different conditions in order to validate the methodology. Besides microstructural analysis, tensile and fatigue tests, all to characterize the material, a pressurized hot water pipe exposed to a series of flow conditions will be evaluated in terms of full-scale testing as well as prognostic evaluation, where the latter will be based on the materials’ data generated, which should prognose changes in the material’s condition, specifically in a pre-cracked stage. This paper provides an overview of the program, while the more material’s related aspects are presented in the subsequent paper.

High-Resolution Characterization of Deformation Induced Martensite in Large Areas of Fatigued Austenitic Stainless Steel Using Deep Learning

“…Deformation-induced martensitic transformation and its impact on the deformation behavior of ASSs during monotonic or cyclic loading via the TRIP or TRIP/TWIP effect has been the subject of numberless studies; for a recent review, see [6,8,11,12,15,16]. Among other areas in which the role of DIM is of outstanding importance, we may include (i) grain refinement via reversion annealing after prior cold working [8,17,18], (ii) magnetic stability at cryogenic temperatures (superconducting magnets) [19,20], (iii) non-destructive monitoring of fatigue damage and assessment of residual fatigue life [21][22][23][24][25], (iv) delayed cracking after deep drawing of lean-nickel alloyed ASSs [26,27], (v) the role of DIM in hydrogen environment embrittlement [28][29][30][31][32], and (vi) pitting corrosion and stress corrosion behavior [33][34][35][36].…”