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Creep rupture and creep behaviour of martensitic X 18 CrMoVNb 11.1 type steel at elevated temperatures and after a temperature transient
Author(s) -
Schirra Manfred
Publication year - 1993
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.199301030
Subject(s) - creep , tempering , materials science , martensite , metallurgy , isothermal process , pearlite , hardening (computing) , composite material , atmospheric temperature range , thermodynamics , microstructure , physics , austenite , layer (electronics)
Martensitic CrMoVNb 1.4914 type steel, which is at present being tested as a material for fuel element wrapper tubes, was subjected to tests in order to find out the impact on the original hardening and tempering strength of brief temperature rises up to 975°C. T ‐transients in the range between 800 and 900°C (20–36 min > A c1b ) do not exert a pronounced influence on creep‐rupture strength; merely the times up to ≤ 1 % creep strain are clearly reduced, as is indicated by creep‐rupture tests at 650°C. There is a more pronounced influence on creep rupture and creep behaviour if the transient extends into the 975°C region and is subsequently held in the range of 600–750°C, where transformation to the pearlite stage occurs. High creep stability is seen at holding temperatures of < 600 and > 400°C. The explanation is furnished by the findings obtained in isothermal creep‐rupture tests above A c1b (800–925°C). Extensive metallographic examination confirms the structural changes expected from the IT‐diagram.