Efekt mikrostruktury na nízkocyklové vlastnosti ODS ocelí

Effect of microstructure on low cycle fatigue properties of ODS steels

článek v časopise - ostatní, Jost

en

Low cycle fatigue properties at room temperature, 650 C and 750 C of three high chromium steels (9%Cr ferritic–martensitic and two 14%Cr ferritic steels) strengthened by oxide dispersion were studied and compared. Cyclic softening/hardening curves, cyclic deformation curves, S–N curves and Coffin–Manson curves are presented together with microstructural observations. Differences in cyclic response, stress level and fatigue life are attributed to differences in the matrix microstructure. The oxide particles stabilize the cyclic response, even if cyclic softening is detected for some experimental conditions. The strength of these steels is discussed in terms of strengthening mechanisms such as grain size effect, particle-dislocations interaction and dislocation density. Comparing three different ODS steels offers an opportunity to tests the contribution of individual mechanisms to the cyclic strength. The reduction of fatigue life in one of the ferritic steels is explained by the presence of large grains, facilitating the fatigue crack nucleation and the early growth.

Nízkocyklové vlastnosti tří chromových ocelí zpevněných oxidickou dispersí byly studovány za pokojové teploty, 650 C a 750 C. Křivky cyklického změkčení/zpevnění, cyklická deformační křivka, S-N křivak a Coffin-Mansonova křivka jsou prezentovány společně s pozorováním mikrostruktury. Oxidické částice cyklicky stabilizují ocell, ačkoliv bylo pozorováno cyklické změkčení pro konkrétní experimentální podmínky. Pevnost těchto ocelí je diskutována z pohledu velikosti zrna, dislokační hustoty a interakcí mezi dislokacemi a oxidickými částicemi. Zkrácení únavového života u jedno z ferritických oceli je vysvětleno přítomností větších zrn, které urychlují nukleaci únavových trhlin.

Low cycle fatigue properties at room temperature, 650 C and 750 C of three high chromium steels (9%Cr ferritic–martensitic and two 14%Cr ferritic steels) strengthened by oxide dispersion were studied and compared. Cyclic softening/hardening curves, cyclic deformation curves, S–N curves and Coffin–Manson curves are presented together with microstructural observations. Differences in cyclic response, stress level and fatigue life are attributed to differences in the matrix microstructure. The oxide particles stabilize the cyclic response, even if cyclic softening is detected for some experimental conditions. The strength of these steels is discussed in terms of strengthening mechanisms such as grain size effect, particle-dislocations interaction and dislocation density. Comparing three different ODS steels offers an opportunity to tests the contribution of individual mechanisms to the cyclic strength. The reduction of fatigue life in one of the ferritic steels is explained by the presence of large grains, facilitating the fatigue crack nucleation and the early growth.

ODS oceli, nízkocyklová únava, fúzní energetika

ODS steels, low cycle fatigue, fusion energy

2012

14.03.2012

0022-3115

424

1

101–108

8