Effects of Alloying Elements on Fracture Properties of Niobium Stabilized Austenitic Steels at Elevated Temperature

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The present work is a further investigation into the effects of the carbon (C), nitrogen (N) and niobium (Nb) contents on then fracture properties of the Type 347 stainless steels at 316oC. 9 heats of systematically designed alloys were examined. Through SEM-EDS, TEM and XRD analyses, two kinds of precipitates, Nb(C,N), CrNbN were identified in the Type 347 steels with a high ratio of wt% N to wt% C, on the other hand only Nb(C,N)s were found in the Type 347 steels with a low ratio of wt% N to wt% C. The tearing moduli were decreased in the range of 52~60% as the carbon content increased from 0.03wt% to 0.05wt%. The tearing moduli were lowered by 52~59% in the alloys with a high nitrogen. It was deduced from the microstructure analysis results that the coarse Nb-rich precipitates control the fracture resistance of the Type 347 as they act as the potential sites for the nucleation of micro-voids.

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Periodical:

Key Engineering Materials (Volumes 345-346)

Edited by:

S.W. Nam, Y.W. Chang, S.B. Lee and N.J. Kim

Pages:

461-464

Citation:

J. H. Yoon et al., "Effects of Alloying Elements on Fracture Properties of Niobium Stabilized Austenitic Steels at Elevated Temperature", Key Engineering Materials, Vols. 345-346, pp. 461-464, 2007

Online since:

August 2007

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$38.00

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[2] P. Marshall: Austenitic Stainless Steels (Elsevier Applied Scinece Publishers Ltd., England 1984).

[3] H. Muesch: Nuclear Engineering and Design Vol. 85 (1985), p.155.

[4] ASTM, Standard Designation E963-95: (ASTM, USA, 2003). wt% N wt% C 0. 03 0. 07 0. 11 0. 02 403 423 445 0. 03 401 425 449 0. 05 403 423 453 Fig. 4. SEM micrograph showing a sectioned specimen after J-R test. Table 2. Ultimate tensile strength of Type 347 stain- steel at 316oC as a function of contents of carbon and nitrogen. Nb(C, N).