Microstructural evolution during high temperature dwell-fatigue of austenitic stainless steels

Nanoindentation characterization on competing propagation between the transgranular and intergranular cracking of 316H steel under creep‐fatigue loading

“…Under the CF loading with dwell time of 1,800 s, a transgranular cracking interlink with pre‐initiated creep void was proposed as fracture mechanism of 316H steel 30 . Moreover, the increased density of geometrically necessary dislocations and formation of numerous recrystallized grains near the transgranular cracking were observed for the 316H steel under the low cycle fatigue loadings 29 .…”

“…However, the CF behaviors and microstructures of the austenite stainless steel (316H) and martensitic steel are totally different. Under CF loading, the cyclic softening behavior and enhanced block grains were observed in martensitic steel, 23–28 while the occurrence of an initial hardening period and small recrystallized grains was reported in the austenite stainless steel 29,30 . Based on these experimental results of the austenitic stainless steel AISI 316, Hales 31 proposed four kinds of damage mechanisms: transgranular cracking (fatigue driven only), intergranular cracking (creep driven only), transgranular cracking interlink with creep voids (CF interaction), and transgranular competing propagation where both fatigue and creep (obey their own failure criteria without interaction).…”

“…Moreover, the increased density of geometrically necessary dislocations and formation of numerous recrystallized grains near the transgranular cracking were observed for the 316H steel under the low cycle fatigue loadings 29 . As for CF test, the formation of tiny recrystallized grains near the main crack 30 could also result in the variation in local mechanical properties, which is unable to be captured by the conventional mechanical testing methods. Nanoindentation technology is widely used to measure the mechanical properties at micro/nano scale, e.g., hardness, elastic modulus, creep resistance, and strain rate sensitivity ( m ), particularly for those heterogeneous structure, thin film, nanopillar, and difficult‐to‐machine specimen 32–35 .…”

Design of a novel creep testing machine to investigate the creep life history of austenitic steel foil at elevated temperature

“…These materials need to have premier long‐term mechanical and sustained properties under elevated temperature, high pressure, and altering environmental parameters such as locations exposed to chloride and water 3–5 . Among the metal alloys, austenitic stainless steels have a spread range of applications for those types of components working in the abovementioned situations 6 . These types of steels with a chromium content of 10.5 wt% or greater possess desirable properties of strength, corrosion resistance, and formability at a competitive price in comparison to nickel‐based and titanium alloys.…”

“…[3][4][5] Among the metal alloys, austenitic stainless steels have a spread range of applications for those types of components working in the abovementioned situations. 6 These types of steels with a chromium content of 10.5 wt% or greater possess desirable properties of strength, corrosion resistance, and formability at a competitive price in comparison to nickel-based and titanium alloys. The addition of 12 wt% of Cr allows a stable chromium oxide layer to cover the alloy surface that protects the base metal from further oxygen attack to some extent.…”