Sanicro® 69: Premium Austenitic Alloy for Nuclear Steam Generators

Sanicro® 69 is an austenitic nickel-chromium-iron alloy used primarily for steam generators in nuclear power plants (PWR). For this application it is used in the 'thermally treated' condition. This treatment results in chromium carbide precipitation at the grain boundaries but no significant chromium depletion. The grade has good structure stability and good weldability.

For the steam generator application the material is characterized by:

Extremely high resistance against stress corrosion cracking in primary side PWR water conditions

Improved pitting corrosion resistance in chloride containing solutions compared with Alloy 600

Sanicro® 69 is also characterized by:

Good corrosion resistance in caustic environments

Excellent performance in nitric acid solutions

For steam generator applications Sanicro® 69 is delivered to the most stringent individual specifications in order to assure maximum reliable performance in nuclear power plants.

More technical information and charts that are relevant to the materials corrosion, mechanical and physical performance are displayed in the figures on the right side of the material page.

Datasheet URL:

Sanicro® 69

Datasheet updated 2020-05-07 13:07 (supersedes all previous editions)

Properties

General

Property	Temperature	Value
Density	23.0 °C	8.12 g/cm³

Mechanical

Property	Temperature	Value	Comment
Elastic modulus	20.0 °C	210 GPa
	100.0 °C	206 GPa
	200.0 °C	201 GPa
	300.0 °C	195 GPa
	400.0 °C	189 GPa
	500.0 °C	182 GPa
	600.0 °C	174 GPa

Elongation	23.0 °C	30 %	min.
Hardness, Vickers	23.0 °C	160 [-]
Tensile strength	20.0 °C	585 MPa	min.
	100.0 °C	550 MPa	min.
	200.0 °C	510 MPa	min.
	300.0 °C	495 MPa	min.
	400.0 °C	490 MPa	min.
	500.0 °C	480 MPa	min.
	600.0 °C	440 MPa	min.
	700.0 °C	340 MPa	min.

Yield strength Rp0.2	20.0 °C	240 MPa	higher values for steam generator tubing in the thermally treated condition can be achieved (280 MPa at 20°C)
	100.0 °C	220 MPa	higher values for steam generator tubing in the thermally treated condition can be achieved (280 MPa at 20°C)
	200.0 °C	190 MPa	higher values for steam generator tubing in the thermally treated condition can be achieved (280 MPa at 20°C)
	300.0 °C	187 MPa	higher values for steam generator tubing in the thermally treated condition can be achieved (280 MPa at 20°C)
	400.0 °C	184 MPa	higher values for steam generator tubing in the thermally treated condition can be achieved (280 MPa at 20°C)
	500.0 °C	180 MPa	higher values for steam generator tubing in the thermally treated condition can be achieved (280 MPa at 20°C)
	600.0 °C	175 MPa	higher values for steam generator tubing in the thermally treated condition can be achieved (280 MPa at 20°C)
	700.0 °C	150 MPa	higher values for steam generator tubing in the thermally treated condition can be achieved (280 MPa at 20°C)

Charpy impact energy	Since Sanicro® 69 is a fully austenitic alloy it possesses good toughness down to -196°C (-320°F)

Thermal

Property	Temperature	Value	Comment
Coefficient of thermal expansion	100.0 °C	1.35E-5 1/K	for 30°C to the mentioned temperature
	200.0 °C	1.4E-5 1/K	for 30°C to the mentioned temperature
	300.0 °C	1.45E-5 1/K	for 30°C to the mentioned temperature
	400.0 °C	1.5E-5 1/K	for 30°C to the mentioned temperature
	500.0 °C	1.55E-5 1/K	for 30°C to the mentioned temperature
	600.0 °C	1.55E-5 1/K	for 30°C to the mentioned temperature

Specific heat capacity	23.0 °C	460 J/(kg·K)
	100.0 °C	480 J/(kg·K)
	200.0 °C	495 J/(kg·K)
	300.0 °C	505 J/(kg·K)
	400.0 °C	510 J/(kg·K)
	500.0 °C	520 J/(kg·K)
	600.0 °C	580 J/(kg·K)

Thermal conductivity	23.0 °C	11 W/(m·K)
	100.0 °C	13 W/(m·K)
	200.0 °C	14 W/(m·K)
	300.0 °C	16 W/(m·K)
	400.0 °C	18 W/(m·K)
	500.0 °C	19 W/(m·K)
	600.0 °C	23 W/(m·K)

Electrical

Property	Temperature	Value
Electrical resistivity	20.0 °C	1.11E-6 Ω·m
	100.0 °C	1.14E-6 Ω·m
	200.0 °C	1.18E-6 Ω·m
	300.0 °C	1.22E-6 Ω·m
	400.0 °C	1.24E-6 Ω·m

Chemical properties

Property	Value	Comment
Aluminium	10 %
Carbon	0.02 %
Chromium	30 %
Cobalt	0.05 %	Lower contents can be specified after agreement.
Iron	Balance
Manganese	0.5 %	max.
Nickel	60 %
Phosphorus	0.02 %	max.
Silicon	0.5 %	max.
Sulfur	0.015 %	max.

Technological properties

Property
Application areas	Sanicro® 69 is used in: Steam generators in nuclear power plants. Units in contact with nitric acid at elevated temperatures. Equipment requiring high resistance to oxidation, carburization and nitriding. Units exposed to caustic solutions at high temperature.
Certifications	Approvals: ASME Boiler and Pressure Vessel Code Case N-20 and N-474 AFCEN RCCM M4105
Cold Forming	The excellent formability of Sanicro® 69 permits cold-bending to very small bending radii. Annealing is normally not necessary after cold-bending owing to the high stress corrosion cracking resistance for Sanicro® 69.
Corrosion properties	Stress corrosion cracking: The thermally treated condition of Sanicro® 69 is developed specifically to resist stress corrosion cracking in steam generator environment at nuclear power plants. This has been confirmed by laboratory stress corrosion cracking tests in pure water (less than 5 ppm oxygen, 4-5 ppm hydrogen added) at 365°C (690°F). No stress corrosion cracking was developed in Sanicro® 69 during the entire test period of 33 000 hours. Alloy 600 started to crack after 200 hours. Intergranular corrosion: Sanicro® 69 has good resistance to intergranular corrosion in both the thermally treated condition and the solution annealed condition. Typical corrosion rates in the Huey test (65% HNO₃, 5 x 48h, ASTM A262 Practice C) are 0.06 mm/year (2.4 mpy). The figure on the right side shows a TTS diagram for a heat of Sanicro® 69 with 0.03% carbon tested in the Huey test. The initial material was annealed at 1040°C (1900°F), 20 min/WQ. As can be seen there is a very narrow area where Sanicro® 69 shows some tendency for sensitization. General corrosion: Sanicro® 69 and Alloy C-276 have been corrosion tested in 20% HNO₃+ 4%HF at 65°C (150°F). Sanicro® 69 had a corrosion rate of 0.625 mm/year (24.6 mpy) while Alloy C-276 suffered a corrosion rate of 23.7 mm/year (933 mpy).
Expanding	Sanicro® 69 is expanded into tube sheets in the same way as standard austenitic stainless steels.
Heat Treatment	For steam generator application the tubes are delivered in the thermally treated conditions. This means exposure at about 720°C (1330°F) for normally 10 hours. Prior to the thermal treatment the tubes are solution annealed at approximately 1100 °C (2010°F) for some minutes. For other applications the tubes are delivered in the solution annealed condition. If additional solution annealing is necessary after further processing the following procedure is recommended: 1050-1150°C (1920-2100°F), 1-10 minutes, rapid cooling in air or water.
Other	Forms of supply: Seamless tube and pipe are supplied in the size range from 1/4" O.D. (6.35 mm) to 4" O.D. (101.6 mm) in wall thickness from 0.030" (0.9 mm) to 1" (25.4 mm). Tube and pipe are delivered in the solution annealed and pickled condition. PWR steam generator tubes are delivered in the bright annealed and thermally treated condition. The thermal treatment involves a treatment in vacuum furnace at about 720°C (1330°F) for normally 10 hours.
Welding	The weldability of Sanicro® 69 is good. Suitable methods of fusion welding are manual metal-arc welding (MMA/SMAW) and gas-shielded arc welding, with the TIG/GTAW method as first choice. For Sanicro® 69, heat-input of <1.0 kJ/mm and interpass temperature of <100°C (210°F) are recommended. A string bead welding technique should be used. Recommended filler metals: TIG/GTAW or MIG/GMAW welding ISO 18274 S Ni 6052/AWS A5.14 ERNiCrFe-7 (e.g. Exaton Ni68HP) MMA/SMAW welding ISO 14172 E Ni 6152/AWS A5.11 ENiCrFe-7 (e.g. Exaton Ni69) Overlay welding: ISO 18274 S Ni 6043/AWS A5.14 ERNiCrFe-14 (e.g. Exaton Ni69HPQ) strip electrode is recommended for overlay welding of tube sheets and high-pressure vessels in cases where corrosion resistance, equal to that of Sanicro® 69, is required.

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