Effect of Mo on High-Temperature Fatigue Behavior of 15CrNbTi Ferritic Stainless Steel

doi:10.1007/s40195-014-0064-0

Abstract

Abstract:

In order to understand the effect of Mo element on the high-temperature fatigue behavior of 15CrNbTi ferritic stainless steel, the stress-controlled fatigue tests have been performed for both 15CrNbTi and 15Cr0.5MoNbTi ferritic stainless steels at 800 °C in laboratory air. The fatigue test results indicate that the fatigue resistance of 15Cr0.5MoNbTi steel is manifestly higher than that of 15CrNbTi steel at the maximum stress below 57 MPa; the 15Cr0.5MoNbTi steel possesses a fatigue limit of 35 MPa, which is higher than that of 15CrNbTi steel. The TEM observations reveal that the Mo element can suppress the formation of coarsened Fe₃Nb₃C precipitates and result in the fatigue resistance enhancement. The dislocation networks formed during the cyclic load favor to improve the fatigue resistance of 15Cr0.5MoNbTi steel at 800 °C.

Key words: Ferritic stainless steel, High-temperature fatigue, Mo, Microstructure

Tianlong Liu, Lijia Chen, Hongyun Bi, Xin Che. Effect of Mo on High-Temperature Fatigue Behavior of 15CrNbTi Ferritic Stainless Steel[J]. Acta Metallurgica Sinica (English Letters), 2014, 27(3): 452-456.

Figures/Tables 6

Table 1 Chemical compositions of two ferritic stainless steels (wt%)

Steel	Cr	Mo	Nb	Ti	C	N	Mn	Si	Fe
15CrNbTi	15.0	–	0.45	0.3	≤0.03	≤0.025	≤1.2	≤1.2	Bal.
15Cr0.5MoNbTi	15.0	0.5	0.45	0.3	≤0.03	≤0.025	≤1.2	≤1.2	Bal.

Fig. 1 Geometry of fatigue specimen (unit: mm)

Fig. 2 Relationship between the maximum stress and number of cycles to failure for 15CrNbTi and 15Cr0.5MoNbTi ferritic stainless steels at 800 °C

Fig. 3 TEM analysis results of Fe2Nb and Fe3Nb3C precipitates in 15CrNbTi steel fatigued at different maximum cyclic stresses: a Fe2Nb, 60 MPa; b Fe2Nb, 60 MPa; c Fe2Nb, 50 MPa; d Fe3Nb3C, 50 MPa

Fig. 4 TEM analysis results of Fe2Nb precipitate in 15Cr0.5MoNbTi steel fatigued at the maximum cyclic stresses of 60 MPa a and 50 MPa b

Fig. 5 Characterizations of dislocation morphology in 15Cr0.5MoNbTi a and 15CrNbTi b steels fatigued at the maximum cyclic stress of 50 MPa

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