Abstract
A comparative evaluation of the low-cycle fatigue (LCF) behavior of type 316LN base metal, 316 weld metal, and 316LN/316 weld joints was carried out at 773 and 873 K. Total strain-controlled LCF tests were conducted at a constant strain rate of 3 × 10−3 s−1 with strain amplitudes in the range ±0.20 to ±1.0 pct. Weld pads with single V and double V configuration were prepared by the shielded metal-arc welding (SMAW) process using 316 electrodes for weld-metal and weld-joint specimens. Optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) of the untested and tested samples were carried out to elucidate the deformation and the fracture behavior. The cyclic stress response of the base metal shows a very rapid hardening to a maximum stress followed by a saturated stress response. Weld metal undergoes a relatively short initial hardening followed by a gradual softening regime. Weld joints exhibit an initial hardening and a subsequent softening regime at all strain amplitudes, except at low strain amplitudes where a saturation regime is noticed. The initial hardening observed in base metal has been attributed to interaction between dislocations and solute atoms/complexes and cyclic saturation to saturation in the number density of slip bands. From TEM, the cyclic softening in weld metal was ascribed to the annihilation of dislocations during LCF. Type 316LN base metal exhibits better fatigue resistance than weld metal at 773 K, whereas the reverse holds true at 873 K. The weld joint shows the lowest life at both temperatures. The better fatigue resistance of weld metal is related to the brittle transformed delta ferrite structure and the high density of dislocations at the interface, which inhibits the growth rate of cracks by deflecting the crack path. The lower fatigue endurance of the weld joint was ascribed to the shortening of the crack initiation phase caused by surface intergranular crack initiation and to the poor crack propagation resistance of the coarse-grained region in the heat-affected zone.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
R. Taillard, S. Degallaix, and J. Foct:Low Cycle Fatigue and Elasto Plastic Behaviour of Materials, K.T. Rie, ed., Elsevier, Munich, 1987, pp. 83–88.
R. Sandstrom, J. Engstrom, J.O. Nilsson, and A. Nordgren:High Temp. Technol., 1989, vol. 7, pp. 2–9.
S. Degallaix, G. Degallaix, and J. Foct:Low Cycle Fatigue, ASTM STP 942, 1988, pp. 798–811.
J.O. Nilsson:Fatigue Eng. Mater. Struct., 1984, vol. 7 (1), pp. 55–64.
B. Vogt, S. Degallaix, and J. Foct:Int. J. Fatigue, 1984, vol. 6 (4), pp. 211–15.
J.O. Nilsson:Scripta Metall., 1983, vol. 17, pp. 593–96.
R. Taillard and J. Foct: inProc. Int. Conf. on High Nitrogen Steels 88, J. Foct and A. Hendry, eds., The Institute of Metals and the Societe Francaise de Metallurgie, Lille, France, 1988, May, pp. 387–91.
S. Degallaix: Ph.D. Thesis, Universite des Sciences et Techniques de Lille, Lille, France, 1986.
J.O. Nilsson and T. Thorvaldsson:Scand. J. Metall., 1985, vol. 15, pp. 83–89.
K. Borst and M. Pohl: inProc. Int. Conf. on High Nitrogen Steels 88. J. Foct and A. Hendry, eds.. The Institute of Metals and the Societe Francaise de Metallurgie, Lille, France, 1988, May, pp. 294–99.
G.A. Honeyman and T.A. Towers: inProc. Int. Conf. on High Nitrogen Steels 88, J. Foct and A. Hendry, eds., The Institute of Metals and the Societe Francaise de Metallurgie, Lille, France, 1988, May, pp. 398–404.
ASME Boiler and Pressure Vessel Code Case N-47. ASME, New York, NY, 1986.
M.O. Malone:Weld. J., 1967, vol. 46, p. 241S.
V.S. Srinivasan, R. Sandhya, K. Bhanu Sankara Rao, S.L. Mannan, and K.S. Raghavan:Int. J. Fatigue, 1991, vol. 13 (6), pp. 471–78.
Erich Folkhard:Welding Metallurgy of Stainless Steels, Springer- Verlag/Wien, New York, NY, 1988, p. 103.
K. Bhanu Sankara Rao, M. Valsan, R. Sandhya, S.L. Mannan, and P. Rodriguez:Met. Mater. Process., 1990, vol. 2, pp. 17–36.
M. Valsan, D.H. Sastry, K. Bhanu Sankara Rao, and S.L. Mannan:Metall. Mater. Trans. A, 1994, vol. 25A, pp. 159–71.
P. Shankar, D. Sundararaman, and S. Ranganathan:Scripta Metall. Mater., 1994, vol. 31 (5), pp. 589–93.
D. Sundararaman, P. Shankar, and V.S. Raghunathan:Metall. Mater. Trans. A, in press.
M. Valsan: Ph.D. Thesis, Indian Institute of Science, Bangalore, 1991.
K. Bhanu, Sankara Rao, M. Valsan, and S.L. Mannan:Mater. Sci. Eng., 1990, vol. A130, pp. 67–82.
A.S. Reddy, S.L. Mannan, V. Seetharaman, and P. Rodriguez:Proc. National Welding Seminar, New Delhi, 1980, paper 21.
J.M. Vitek, S.A. David, D.J. Alexlander, J.R. Keiser, and R.K. Nanstad:Acta Metall., 1991, vol. 39 (4), pp. 503–16.
K. Bhanu Sankara Rao, M. Valsan, R. Sandhya, S.L. Mannan, and P. Rodriguez:High Temp. Mater. Process., 1986, vol. 7, pp. 171–77.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Valsan, M., Sundararaman, D., Rao, K.B.S. et al. A comparative evaluation of low-cycle fatigue behavior of type 316LN base metal, 316 weld metal, and 316LN/316 weld joint. Metall Mater Trans A 26, 1207–1219 (1995). https://doi.org/10.1007/BF02670616
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF02670616