Paper Title:

Creep Strain Behavior in Transient Region and Minimum Creep Rate of Tempered Martensitic 9%Cr Steel

Periodical Materials Science Forum (Volumes 638 - 642)
Main Theme THERMEC 2009
Edited by T. Chandra, N. Wanderka, W. Reimers , M. Ionescu
Pages 47-52
DOI 10.4028/www.scientific.net/MSF.638-642.47
Citation Fujio Abe, 2010, Materials Science Forum, 638-642, 47
Online since January, 2010
Authors Fujio Abe
Keywords 9Cr Steel, Boron, Creep Rate, Dislocation, Fe2W Laves Phase, M23C6 Carbide, Martensite, MX Carbonitride, Transient Creep
Article Preview
View full size
Abstract

The effect of fine precipitates, excess dislocations and sub-boundary hardening on creep strain behavior in the transient region has been investigated for tempered martensitic 9%Cr steel at 600 and 650oC. The fine precipitates that form during tempering or during creep decrease the creep rate in the transient region, while excess dislocations produced by cold rolling promote the recovery of dislocations during creep, resulting in higher creep rates. The sub-boundary hardening is enhanced by fine precipitates along lath and block boundaries, which retards the onset of acceleration creep. The movement and annihilation process of dislocations in the transient region is controlled by not only the movement of dislocations in the matrix but also the absorption of dislocations at boundaries. The minimum creep rate is basically determined by the time to minimum creep rate.