Effect of stress and temperature on the creep and rupture behavior of a 1. 25% chromium--0. 5% molybdenum steel

Conference · Wed Jun 01 04:00:00 EDT 1977 · Metall. Trans., A; (United States)

OSTI ID:7218889

Viswanathan, R

The creep and stress rupture behavior of a normalized 1.25 percent chromium-0.5 percent molybdenum steel has been investigated over a temperature (T) range of 510 to 620/sup 0/C and a stress (sigma) range of 65 to 425 MN/m/sup 2/. The creep rate (epsilon-dot) and time to rupture (t/sub r/) data have been analyzed in terms of the general expression epsilon-dot or t/sub r/ = A sigma/sup n/ exp (Q/RT), where A is a constant, n is the power exponent of stress, Q is an empirical activation energy for the rate controlling process and R is the universal gas constant. At each temperature, the logarithmic plots of creep rate and time to rupture as functions of stress consist of two linear segments, separating the data into low stress and high stress regimes. The stress exponent has approximate values of 4 and 10 in the low stress and high stress regimes respectively in the appropriate expressions for both creep rate and for time to rupture. The activation energy has values of 367 and 420 kJ/mole in the low stress regime for time to rupture and creep rate respectively. In the high stress regime, the respective values of activation energy are 581 and 670 kJ/mole. Fractographic observations show that the changes from low stress to high stress behavior in creep rate and time to rupture approximately coincide with the transition in fracture mode from intergranular to transgranular cracking as well as with the transition in the rupture ductility from a region of linear variation with stress to one of constant ductility. These observations suggest that the transition from low stress to high stress behavior may be associated with a change in deformation mode from predominantly grain boundary sliding at low stress to transgranular matrix deformation at high stress.

• Research Organization: Westinghouse Research Labs., Pittsburgh
• OSTI ID: 7218889
• Conference Information: Journal Name: Metall. Trans., A; (United States) Journal Volume: 8:6
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
ALLOYS
CHROMIUM ALLOYS
CHROMIUM STEELS
CHROMIUM-MOLYBDENUM STEELS
CREEP
FAILURES
IRON ALLOYS
IRON BASE ALLOYS
MECHANICAL PROPERTIES
RUPTURES
STEELS
STRESSES
TEMPERATURE DEPENDENCE