In order to investigate the behavior of elevated temperature low cycle fatigue crack propagation in Type 304 stainless and 2.5Ni-0.5Mo-0.1V ferritic steels, load-controlled low-cycle fatigue tests were carried out on notched specimens under four kinds of loading waveform (i, e
., PP-, PC-, CP- and CC-types).
The results obtained were summarized as follows:
(1) Type 304 stainless steel
The crack propagation rate, dl/dN
, was correlated well with the fatigue J-integral range, ΔJf
, in P-type (i, e
., PP- and PC- types) fatigue tested at 973K and 823K. The striations, of which width was found to be nearly equal to dl/dN
, were observed on their fracture surfaces.
On the other hand, dl/dN
in C-type (i. e
., CC- and CP-types) fatigue tested at 973K was correlated well with the creep J-integral range, ΔJc
. The fracture mode in this case was of intergranular type. However, good correlation of dl/dN
as well as ΔJf
wasn't obtained in C-type fatigue at 823K, where the fracture mode was of mixed (i, e
., intergranular and transgranular) type. This appeared to be caused by creep-fatigue interaction.
(2) Ni-Mo-V steel
In the same way of the above stainless steel, dl/dN
in P- and C-type fatigue at 823K were correlated well with ΔJf
, respectively. However, there was no difference in fracture mode between these two types, both of which exhibited the transgranular fracture mode.