On massive carbide precipitation during high temperature low cycle fatigue in alloy 800H

Journal Article · Mon Aug 15 04:00:00 EDT 1994 · Scripta Metallurgica et Materialia; (United States)

OSTI ID:7167297

Bhanu Sankara Rao, K; Halford, G R ^[1]; Schuster, H ^[2]

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1. National Aeronautics Space Agency, Cleveland, OH (United States). Lewis Research Center
2. KFA, Juelich (Germany). Inst. for Reactor Materials

Alloys engineered for high-temperature application are frequently put into use in a thermodynamically unstable condition. Subsequent exposure to service temperatures may promote many thermally-assisted reactions such as formation, coarsening, and/or coalescence of precipitates. Superposition of cyclic straining may accelerate the kinetics of these reactions but also may cause reaction products having specific features not observed under simple thermal exposure. The influence of cyclic strain-induced microstructural changes on the fatigue behavior has to be considered in terms of their effects on both cyclic strength and life. The occurrence of massive (cellular) precipitation of M[sub 23]C[sub 6] on grain boundaries during elevated temperature low cycle fatigue testing has been reported in Type 304 stainless steel, Type 316 stainless steel, and Inconel 617 superalloy, and its presence has already been linked with reduction in high temperature ductility, an important engineering property on which low cycle fatigue (LCF) life depends to a large extent. Massive precipitation may render the austenitic engineering alloys susceptible to corrosion, which would have important bearing on the performance of these alloys in the oxidizing environments. Furthermore, the long term stability of massive M[sub 23]C[sub 6] particles is particularly important since the transformation of such a large structure into a brittle intermetallic phase (such as sigma) could produce a detrimental effect on the mechanical properties. The conditions and the mechanisms responsible for the occurrence of massive precipitation during LCF have not yet been established. This investigation is specifically aimed at understanding the influence of strain rate on massive precipitation and the mechanism responsible for the occurrence of massive M[sub 23]C[sub 6] precipitation in Alloy 800H during elevated temperature LCF testing.

• OSTI ID: 7167297
• Journal Information: Scripta Metallurgica et Materialia; (United States), Journal Name: Scripta Metallurgica et Materialia; (United States) Vol. 31:4; ISSN 0956-716X; ISSN SCRMEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102 -- Metals & Alloys-- Structure & Phase Studies
360103* -- Metals & Alloys-- Mechanical Properties
ALLOY-FE44NI33CR21
ALLOYS
ALUMINIUM ADDITIONS
ALUMINIUM ALLOYS
CARBIDES
CARBON COMPOUNDS
CHROMIUM ALLOYS
COBALT ALLOYS
CORROSION RESISTANT ALLOYS
CRYSTAL-PHASE TRANSFORMATIONS
DATA
ELECTRON MICROSCOPY
EXPERIMENTAL DATA
FATIGUE
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
INCOLOY 800H
INCOLOY ALLOYS
INFORMATION
IRON ALLOYS
IRON BASE ALLOYS
LIFETIME
MATERIALS
MECHANICAL PROPERTIES
MICROSCOPY
MICROSTRUCTURE
NICKEL ALLOYS
NUMERICAL DATA
PHASE TRANSFORMATIONS
PRECIPITATION
SEPARATION PROCESSES
SERVICE LIFE
THERMAL FATIGUE
TI
TITANIUM ADDITIONS