INCOLOY alloy 925

INCOLOY alloy 925 Description

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INCOLOY alloy 925 is designated as UNS N09925. Designations and specifications for the product include NACE MR-01-75, ASME Boiler and Pressure Vessel Code Case 2218 Section VIII Division 1, and Special Metals Corporation internal specification HA 46. Alloy 925 is available as tube, round bar, flat bar and forging stock.

 

INCOLOY alloy 925 Characteristics

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INCOLOY® alloy 925 (UNS N09925) is an age- hardenable nickel-iron-chromium alloy with additions of molybdenum, copper, titanium and aluminum. The alloy’s chemical composition, listed in Table 1, is designed to provide a combination of high strength and excellent corrosion resistance. The nickel content is sufficient for protection against chloride-ion stress- corrosion cracking. The nickel, in conjunction with the molybdenum and copper, also gives outstanding resistance to reducing chemicals. The molybdenum aids resistance to pitting and crevice corrosion. The alloy’s chromium content provides resistance to oxidizing environments. The titanium and aluminum additions cause a strengthening reaction during heat treatment.

 

INCOLOY alloy 925 APPLICATIONS

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INCOLOY alloy 925 is used in various applications requiring a combination of high strength and corrosion resistance. Because of the alloy’s resistance to sulfide stress cracking and stress-corrosion cracking  in  “sour”  (H2S  containing)  crude  oil  and natural gas, it is used for down-hole and surface gas-well components including tubular products, valves, hangers, landing nipples, tool joints and packers. The alloy is also useful for fasteners, marine and pump shafting and high-strength piping systems.

 

Alloy 925 INCOLOY Chemical Composition

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The following table shows the chemical composition of Incoloy(r) alloy 925™.

Elemeents	Content (%)
Nickel, Ni	44
Iron, Fe	28
Chromium, Cr	21
Molybdenum, Mo	3
Titanium, Ti	2.1
Copper, Cu	1.8
Aluminum, Al	0.3
Carbon, C	0.01

 

INCOLOY alloy 925 Heat Treatment

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Solution annealing in preparation for age hardening should be done at 1800-1900°F (980-1040°C) for a minimum of 30 min and a maximum of 4 h. Cool at a rate equivalent to air cooling, or faster, for sizes of 1 in (25 mm) or under. Water quench all sizes over 1 in (25 mm).

The following age hardening treatment is normally used: 1350-1380°F (732-749°C)/6-9 h, FC to 1150°F (621°C), hold at 1150°F (621°C) ± 15°F (8°C) for a total aging time of 18 h. Cool at a rate equivalent to air cooling, or faster.

 

Tensile Properties of INCOLOY alloy 925

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Form/Condition	Tensile Strength		Yield Strength (0.2% Offset)		Elongation	Hardness*
	ksi	M P a	ksi	M P a	%	Rockwell
Round/Solution-Annealed	99.3	685	39.3	271	56	76 B
Round/Solution-Annealed and Aged	167.3	1154	120.6	832	27	32 C
Cold Drawn Tubing/Solution- Annealed and Aged	172.5	1189	120.4	830	27	35 C

All values meet the requirements of NACE Standard MR0175.

 

Mechanical Property Limits for INCOLOY alloy 925

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Solution-Annealed and Aged Material SMC internal specification HA 46)

Condition	Diameter		Tensile Strength minimum		Yield Strength (0.2% offset) minimum		Elongation in 2 in (50.8 mm) or 4D min.	Reduction of Area minimum	Impact Strength1 min. average		Hardness2 Rockwell C
	in	mm	ksi	MPa	ksi	MPa	%	%	ftlbf	kgf m	min.	max.
Cold Worked	5/8 to 3.0	15.9 to 76.2	140	965	105	724	18	25	35	4.85	26	38
Hot Worked	1 to 10	25.4 to 254	140	965	110	758	18	25	35	4.85	26	38

Charpy V-Notch - Impact tests performed at -75 F (-60 C), in accordance with ASTM E23. 

 

INCOLOY alloy 925 Corrosion Resistance

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INCOLOY alloy 925 has a high level of corrosion resistance. In both reducing and oxidizing environments, the alloy resists general corrosion, pitting, crevice corrosion, intergranular corrosion and stress-corrosion cracking. Some environments in which INCOLOY alloy 925 is particularly useful are “sour” (H2S containing) crude oil and natural gas, sulfuric acid, phosphoric acid, and seawater. The performance of INCOLOY alloy 925 under conditions representing sour gas wells is indicated in Figure 6 and Tables 8, 9 and 10. Figure 6 shows resistance to stress- corrosion cracking in a sour environment at high pressure and temperature. Table 8 shows that the alloy resists sulfide stress cracking, a form of hydrogen embrittlement. The tests involve exposure of stressed C-ring specimens (made from a portion of tubing cross section) to a solution containing hydrogen sulfide, sodium chloride and acetic acid.

 

INCOLOY alloy 925 Metallurgy

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INCOLOY alloy 925 is an austenitic nickel-iron-chromium alloy made precipitation hardenable by additions of titanium and aluminum. The precipitation-hardening (age- hardening) heat treatment causes precipitation of gamma prime phase, Ni3 (Al, Ti). The phase greatly increases both the hardness and strength of the alloy. Exposure to elevated temperatures also causes formation of other phases, including eta and sigma. Figure 4 is a time-temperature-transformation diagram, and Figure 5 shows effects of the phases on impact strength of the solution-annealed plus aged alloy.

 

INCOLOY alloy 925 Hot & Cold Forming

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The hot working range for the alloy is 1600 to 2150°F (870 to 1175°C). At temperatures up to 2000°F (1095°C), INCOLOY alloy 925 has hot-working characteristics similar to those of INCOLOY alloy 825. For maximum corrosion resistance and highest strength after direct aging, final hot working should be done in the 1600 to 1800°F (870 to 980°C) range.

The cold-forming behavior of INCOLOY alloy 925 is similar to that of INCOLOY alloy 825 except that alloy 925 has a higher work-hardening rate.

 

INCOLOY alloy 925 Machining

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INCOLOY alloy 925 is an age hardenable alloy with good machinability in the solution-annealed or aged conditions. Rigid tools with positive rake angles and techniques that minimize work hardening of the material are required. Cemented carbide tools produce the highest cutting rates and are recommended for most turning operations involving uninterrupted cuts. High speed steel tools may be used for interrupted cuts, finishing to close tolerances, finishing with the smoothest surfaces, and cutting with the least amount of work hardening. Best results are obtained by rough machining before age hardening and finishing after heat treatment.

 

INCOLOY alloy 925 Drilling

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Steady feed rates minimize excessive work hardening during drilling. Heavy-duty, high speed drills with a heavy web are recommended. For twist drilling, recommended surface speeds are 20-30 ft/min (6-9 m/min) for the solution- annealed condition and 8-10 ft/min (2.4-3.0 m/min) for the aged condition. Feed rates range from 0.005 in/rev (0.13  mm/rev) to 0.015 in/rev (0.4 mm/rev) depending on the drill size. For gun drills [sizes from 1/16 in (1.6 mm) to 2 in (50 mm)], a feed rate of 0.0001-0.003 in/rev (0.0025-0.08 mm/rev) is recommended for both the solution-annealed and aged conditions. The surface speed should be kept at about 220 ft/min (67 m/min) for solution-annealed material and 60 ft/min (18 m/min) for material in the aged condition.