Einfluss der Testatmosphäre auf die Kriechrissentstehung und das Risswachstum in kommerziellen Hochtemperaturlegierungen
Einfluss der Testatmosphäre auf die Kriechrissentstehung und das Risswachstum in kommerziellen Hochtemperaturlegierungen
The influence of surface cracks caused by corrosion on the creep rupture properties of the alloys INCOLOY 8ooH and INCONEL 617 has been investigated for temperatures in the range 1o73 K to 1223 K. The test environments were air and impure helium simulating the primary coolant gas of a high temperatu...
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Personal Name(s): | Yun, H. M. (Corresponding author) |
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Schuster, H. / Ennis, P. J. / Nickel, Hubertus | |
Contributing Institute: |
Publikationen vor 2000; PRE-2000; Retrocat |
Imprint: |
Jülich
Kernforschungsanlage Jülich GmbH, Zentralbiliothek, Verlag
1984
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Physical Description: |
190 p. |
Document Type: |
Report Book |
Research Program: |
ohne Topic |
Series Title: |
Berichte der Kernforschungsanlage Jülich
1939 |
Link: |
OpenAccess |
Publikationsportal JuSER |
The influence of surface cracks caused by corrosion on the creep rupture properties of the alloys INCOLOY 8ooH and INCONEL 617 has been investigated for temperatures in the range 1o73 K to 1223 K. The test environments were air and impure helium simulating the primary coolant gas of a high temperature reactor (HTR helium). The depths o-fsurface cracks in creep test specimens were measured metallographically and a characteristic crack depth, a$_{90}$ , was derived a$_{90}$ is defined so that 9o % of the cracks present have depths below a$_{90}$. The dependence of a$_{90}$ on test time, creep strain and stress wäs examined: - the surface crack depth as a function of creep strain showed that in both test environments there was an incubation strain in which no surface cracks caused by gas-metal interactions could be detected. - following the incubation period, the surface crack depth increased to a value which is approximately the same as the grain diameter. The growth rate of the cracks showed a minimum value at this point, andonly began to increase again shortly before rupture of the specimen. - at a given creep strain, after a few hundred hours stable crack depths were determined, which remained independent of the test time. The growth of creep cracks at the specimen surface as a function of the creep strain was described analytically. This allowed the stress increase due to loss of specimen cross section by surface crack formation to be estimated. It was shown that the surface cracks resulting from corrosion lead to an increase in the creep rate at creep strains above 5 %, but the increases were similar in both atmospheres. Rupture of the specimens occurred when the surface cracks and voids developed inside the specimen due to the creep damage processes. This is the main reason for the similar creep rupture properties of the alloys in the two test environments. Finally, a method has been developed to allow the plotting of the depth of surface cracks caused by corrosion with the stress-rupture curves. In this type of diagram, the damage resulting from surface cracks can be related to the creep rupture data to indicate whether corrosion effect s need to be considered the derivation of design stresses. |