Chemical Composition Effects on the Creep of Austenitic Stainless Steel Weld Metals
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
The effect of titanium, boron, and phosphorus on the creep-rupture properties of type 308 stainless steel, type 316 stainless steel, and 16-8-2 weld metals were studied. Creep-rupture tests were made at 649°C on specimens taken from gas tungsten arc welds deposited by use of commercial and experimental weld filler wires. Additions of about 0.4 and 0.8% Ti to the commercial composition for type 308 stainless steel increased its strength and ductility over those of welds made with a commercial filler wire. A maximum in the effect of titanium was apparent: the 0.4% Ti alloy had better strength and ductility. Although small additions of boron and phosphorus had only a minor effect on strength and ductility when added to the commercial composition separately or in combination, the addition of approximately 0.006% B and 0.042% P to a 0.4% Ti alloy significantly increased its strength above that of the 0.4% Ti alloy without boron and phosphorus. A similar effect of titanium was observed for type 316 stainless steel: boron and phosphorus additions had little effect on strength and ductility above the effect of the optimum titanium additions. The results for the type 16-8-2 weld metal were not as unequivocal. Although additions of titanium and titanium plus boron and phosphorus again favorably affected the strength and ductility, there were significant strength variations among the welds. The microstructures of the welds were examined, and the differences were characterized in terms of the {delta}ferrite morphologies. Although the microstructures of the weld metals were significantly different from comparable base-metal compositions, the effect of titanium on strength in the weld was similar to the effect of titanium in austenitic stainless steel base metals (with no {delta}ferrite). Similar observations were made on the effects of boron and phosphorus. Possible explanations of these effects are proposed.
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-00OR22725; W-7405-ENG-26
- OSTI ID:
- 707303
- Report Number(s):
- ORNL--5840
- Country of Publication:
- United States
- Language:
- English
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