Fatigue strength scatter characteristics of JIS SUS630 stainless steel with duplex S–N curve

Abstract

The scatter behavior of fatigue strength for 17-4 PH stainless steel (JIS SUS630, equivalent to ASTM-A563 Grade 630), which exhibited a duplex S-N curve, was investigated. It was found that the fatigue strength scatter of the SUS630 at 10 6 and 10 7 cycles, which were corresponding to the fatigue strengths for the surface-induced and the subsurface-inclusion-induced crack nucleation modes, respectively, were significantly small and comparable to each other. The scatter of inclusion size in the present material was small and resulted in the small scatter of fatigue strength comparable to that for the surface-induced crack nucleation mode. The variation in size of non-metallic inclusions is known as one of the main factors for the fatigue strength scatter [1]. It was also found that the scatter of fatigue strength was in the same order of tensile strength.

Is the temperature plateau of a self‐heating test a robust parameter to investigate the fatigue limit of steels with thermography?

“…In fact, referring to Figure at loading level in the plastic regime (145 MPa) near the failure, the maximum temperature variation of duplex steel is approximately of 1°C, while 3.5°C at 115 MPa and 2°C at 220 MPa were obtained for AISI 316 and 17‐4 PH, respectively. It is worth noting that the temperature variations of austenitic and martensitic stainless steels are in agreement with the temperature changes reported in literature …”

“…It is worth noting that the temperature variations of austenitic and martensitic stainless steels are in agreement with the temperature changes reported in literature. [4][5][6]23,32 The temperature variation of duplex is lower than in austenitic and martensitic material, even if the material experiences large deformations, as represented by Figure 13. In this figure, in effect, the ductile behaviour of duplex is confirmed: the deformation (170 mm) is nearly equivalent to that of AISI 316 which is 200 mm.…”

“…To verify the proposed approach, 3 stainless steels were investigated by performing fatigue tests at R = 0.5 with a stepwise loading procedure, the AISI 316, 17‐4 PH and ASTM A 890 grade 4a steels, respectively, fully austenitic, fully martensitic, and biphasic austeno‐ferritic steels used in the gas and oil industrial field. All the aspects concerning the mechanical characterization of austenitic AISI 316 and martensitic 17‐4 PH are extensively described in other works . ASTM A 890 grade 4a consists of austenitic clusters of grain embedded into a ferritic lattice: the presence of both austenite and ferrite promotes a global heterogeneity.…”

“…All the aspects concerning the mechanical characterization of austenitic AISI 316 and martensitic 17-4 PH are extensively described in other works. [4][5][6]23,32 ASTM A 890 grade 4a consists of austenitic clusters of grain embedded into a ferritic lattice: the presence of both austenite and ferrite promotes a global heterogeneity. The texture of the material is composed by lattice mismatch, 24 lattice discontinuities (grain interfaces, distribution of grain orientation, and interstitial/ substitutional atoms in the matrix 25 ), and different grain shapes ("equiassic" or "columnar/elongated").…”

Analysis of selected mathematical models of high-cycle S-N characteristics

“…Also compared were the results obtained for steel SUS630 (EN equivalent: X5CrNiCuNb16-4). The description of tests performed on this material can be found in the paper MOHD et al (2015). The tests were performed on smooth samples, at stress frequency of 100 Hz.…”