Inconel 617 (UNS N06617) – Nickel-Chromium-Cobalt-Molybdenum Alloy for Extreme High-Temperature Service

Short Description:

Inconel 617 (UNS N06617 / W.Nr. 2.4663 / NiCr22Co12Mo9) is a nickel-chromium-cobalt-molybdenum solid-solution strengthened superalloy specifically designed for ultra-high-temperature service up to 1150°C (2100°F) . Womic Steel supplies Inconel 617 in multiple product forms including seamless pipe, welded pipe, steel bar, steel plate, steel coil, strip, flanges, fittings, forgings, wire, and valves for advanced nuclear reactors, gas turbines, aerospace propulsion systems, and petrochemical processing applications .

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Product Overview

The alloy was developed for applications requiring the highest temperature capability among commercially available nickel-based superalloys. The unique combination of high chromium (20-24%) for oxidation resistance, cobalt (10-15%) for solid-solution strengthening and thermal fatigue resistance, and molybdenum (8-10%) for creep strength creates a material that maintains structural integrity and oxidation resistance at temperatures where most other alloys would fail. Inconel 617 is rated for service up to 1100°C with excellent resistance to oxidation and carburization at temperatures up to 1150°C.

Key characteristics include:

Exceptional high-temperature strength up to 1150°C (2100°F)
Superior oxidation resistance in air and aggressive atmospheres
Excellent resistance to carburization and nitridation at elevated temperatures
Outstanding creep-rupture strength at temperatures above 800°C
Good resistance to thermal fatigue and thermal cycling
Excellent resistance to sulfur-containing atmospheres
Good weldability and fabricability with proper procedures

Chemical Composition

Element	UNS N06617 (ASTM)	Role
Nickel (Ni)	44.5 – 55.5	Base element, provides corrosion resistance and austenitic stability
Chromium (Cr)	20.0 – 24.0	Forms protective Cr₂O₃ oxide scale for oxidation resistance
Cobalt (Co)	10.0 – 15.0	Solid-solution strengthening, improves thermal fatigue resistance
Molybdenum (Mo)	8.0 – 10.0	Solid-solution strengthening, creep resistance, corrosion resistance
Aluminum (Al)	0.8 – 1.5	Enhances oxidation resistance by forming Al₂O₃ protective layer
Iron (Fe)	≤ 3.0	Impurity, tightly controlled
Carbon (C)	0.05 – 0.15	Carbide former for grain boundary strengthening
Manganese (Mn)	≤ 1.0	Deoxidizer
Silicon (Si)	≤ 1.0	Deoxidizer
Titanium (Ti)	≤ 0.6	Grain boundary strengthening, carbide former
Phosphorus (P)	≤ 0.015	Impurity
Sulfur (S)	≤ 0.015	Impurity

Mechanical Properties

Room Temperature Properties (Annealed)

Property	Value
Tensile Strength	≥ 680 MPa (98.6 ksi)
Yield Strength (0.2% Offset)	≥ 300 MPa (43.5 ksi)
Elongation	≥ 30%
Hardness	≤ 240 HB
Density	8.36 g/cm³
Melting Range	1332 – 1380°C
Thermal Conductivity at 20°C	13.4 W/m·K
Coefficient of Thermal Expansion (20-100°C)	11.6 × 10⁻⁶/°C
Elastic Modulus	211 GPa

High-Temperature Mechanical Properties

Temperature °C	Tensile Strength (MPa)	0.2% Yield Strength (MPa)	1.0% Yield Strength (MPa)
100	650	270	300
200	620	230	260
300	600	220	250
400	570	210	240
500	540	200	225
600	510	190	210
700	400	185	205
750	340	180	200

Key Advantages of Inconel 617

Exceptional High-Temperature Strength – Inconel 617 maintains its structural integrity at temperatures up to 1150°C (2100°F). The combination of solid-solution strengthening from molybdenum, cobalt, and chromium provides outstanding creep-rupture strength at temperatures where most other superalloys have already softened. At 1000°C, the 1000-hour creep-rupture strength exceeds 100 MPa, making it suitable for long-term service in ultra-high-temperature applications.

Superior Oxidation Resistance – The alloy forms a protective dual oxide scale of Cr₂O₃ and Al₂O₃ that provides exceptional resistance to oxidation at temperatures up to 1150°C. The aluminum content (0.8-1.5%) enhances oxidation resistance by forming a tightly adherent Al₂O₃ layer that resists spalling even under severe thermal cycling conditions. In 1100°C air oxidation tests, Inconel 617 demonstrates minimal weight gain compared to other superalloys.

Outstanding Resistance to Carburization and Nitridation – In high-temperature environments containing carbon or nitrogen (ethylene cracking furnaces, ammonia synthesis plants), Inconel 617 effectively resists the diffusion of carbon and nitrogen into the matrix, preventing embrittlement and extending component life significantly.

Excellent Thermal Fatigue Resistance – The high cobalt content (10-15%) improves resistance to thermal fatigue, making the alloy suitable for components subjected to severe temperature cycling. This property is particularly valuable in gas turbine combustion chambers and industrial furnace components where rapid heating and cooling cycles occur.

Good Creep-Rupture Strength – The alloy exhibits outstanding creep resistance at elevated temperatures, with rupture life exceeding 1000 hours under 100 MPa stress at 1000°C. This makes Inconel 617 the preferred material for critical high-temperature components requiring long-term reliability.

Resistance to Sulfur-Containing Environments – Inconel 617 performs well in sulfur-containing oxidizing atmospheres, making it suitable for combustion, waste incineration, and petrochemical applications where sulfur compounds are present.

Inconel 617 vs Inconel 625 vs Inconel 600: Comparison

Property	Inconel 600	Inconel 625	Inconel 617
Nickel Content	≥ 72%	≥ 58%	44.5-55.5%
Chromium Content	14-17%	20-23%	20-24%
Cobalt Content	None	≤ 1.0%	10-15%
Molybdenum Content	None	8-10%	8-10%
Aluminum Content	None	≤ 0.4%	0.8-1.5%
Strengthening Mechanism	Solid-solution	Solid-solution	Solid-solution (Co, Mo)
Max Operating Temp	1093°C	982°C	1150°C
Oxidation Resistance	Excellent	Excellent	Superior
Creep Resistance	Good	Good	Outstanding
Thermal Fatigue Resistance	Good	Good	Excellent
Primary Applications	Chemical, nuclear, heat treat	Marine, chemical, FGD	Nuclear, gas turbine, extreme high-temp

When to choose Inconel 617: Applications requiring ultra-high-temperature service above 1000°C, gas turbines, advanced nuclear reactors (VHTR), superheater tubing, petrochemical reformers, and components subject to severe thermal cycling at extreme temperatures.

Heat Treatment of Inconel 617

Inconel 617 is a solid-solution strengthened alloy that does not respond to precipitation hardening. The standard heat treatment is designed to achieve optimal microstructure for creep resistance:

Solution Annealing (Standard):

Temperature: 1150 – 1200°C (2100 – 2190°F)
Soaking Time: 30-60 minutes (depending on thickness)
Cooling: Water quench (rapid cooling) – mandatory for maximum creep resistance
Purpose: Dissolve carbides, achieve uniform austenite, optimize creep resistance
Note: For thickness below 1.5mm, rapid air cooling may be acceptable

Stress Relief Annealing:

Temperature: Up to 870°C (1600°F)
Cooling: Air cool
Purpose: Relieve residual stresses from cold working without affecting creep resistance

Available Product Forms from Womic Steel

Seamless Pipe & Seamless Tube

Outside Diameter: 6mm – 300mm
Wall Thickness: 1mm – 30mm
Length: Up to 12m
Standards: ASTM B167, ASME SB-167
Applications: High-temperature process piping, heat exchanger tubes, nuclear reactor components, gas turbine fuel lines
Keywords: Inconel 617 seamless pipe, UNS N06617 tube, 2.4663 pipe, high temperature nickel alloy tube

Welded Pipe

Outside Diameter: 50mm – 1200mm
Wall Thickness: 1.0mm – 25mm
Standards: ASTM B517, ASTM B516
Applications: Large-diameter furnace components, process piping, heat exchanger shells
Keywords: Inconel 617 welded pipe, large diameter nickel pipe

Steel Bar (Round, Square, Flat)

Diameter: 6mm – 300mm
Surface: Hot rolled, Bright (cold drawn), Ground, Turned
Standards: ASTM B166, AMS 5887
Applications: Shafts, valve stems, fasteners, turbine bolts, machined components
Keywords: Inconel 617 round bar, N06617 bar stock, nickel alloy bar, high temperature bar

Steel Plate & Sheet

Thickness: 1mm – 100mm
Width: Up to 2000mm
Standards: ASTM B168, AMS 5889, ASME SB-168
Applications: Vessel shells, heat exchanger plates, structural components, flange blanks, combustion chamber components
Keywords: Inconel 617 plate, Inconel 617 sheet, N06617 plate, high temperature alloy plate

Steel Coil & Strip

Thickness: 0.5mm – 6.0mm
Width: 10mm – 1000mm
Standards: ASTM B168
Applications: Formed components, bellows, expansion joints, thin-walled tubing, stampings
Keywords: Inconel 617 coil, nickel alloy strip, high temperature strip

Flanges & Fittings

Types: Weld Neck, Slip-On, Blind, Socket Weld, Threaded
Sizes: 1/2" – 24"
Pressure Rating: Class 150 – Class 2500
Standards: ASTM B564, ASME B16.5
Keywords: Inconel 617 flanges, nickel alloy fittings

Forgings

Types: Rings, disks, shafts, valve bodies, turbine components, custom geometries
Weight: Up to 3,000kg per piece
Standards: ASTM B564, AMS 5887
Keywords: Inconel 617 forging, forged ring, turbine component forging

Inconel 617 Valves

Types: Ball valves, Gate valves, Globe valves, Check valves
Sizes: 1/2" – 12"
Pressure Rating: Class 150 – Class 2500
Temperature Range: -196°C to +1100°C
Design Standards: API 608, API 6D, ASME B16.34
Actuation: Manual, Pneumatic, Electric
Applications: Ultra-high-temperature process isolation, gas turbine control, nuclear reactor coolant systems

Fabrication Considerations

Hot Working: Inconel 617 has good hot workability. Recommended processing temperature range is 900-1150°C. Fuel sulfur content must be tightly controlled: natural gas <0.1% sulfur, heavy oil <0.5% sulfur. Hot working should be followed by solution annealing and rapid cooling.

Cold Working: The alloy has a high work hardening rate. Cold working should be performed with intermediate annealing steps. Work hardened material retains useful strength at elevated temperatures.

Welding: Inconel 617 has good weldability using GTAW (TIG), GMAW (MIG), and SMAW (stick welding) processes. Recommended filler metal: ERNiCrCoMo-1 (matching composition). Preheating is generally not required. Control interpass temperature ≤150°C. Use low heat input and multi-pass techniques for heavy sections.

Machining: Inconel 617 is a difficult-to-machine alloy due to its high strength and low thermal conductivity. Use carbide or ceramic tools, low cutting speeds, moderate feed rates, and adequate coolant. Avoid tool dwell to prevent work hardening.

Applications of Inconel 617

Advanced Nuclear Reactors – Inconel 617 is a primary candidate material for Very High Temperature Reactors (VHTR) and Molten Salt Reactors (MSR) in Generation IV nuclear designs. The alloy is specified for reactor pressure vessels, intermediate heat exchangers, steam generator tubing, and helium-helium heat exchanger components operating at temperatures above 900°C.

Gas Turbine Power Generation – The alloy is used in advanced gas turbine combustion chambers, combustor cans, transition ducts, turbine casings, and hot section components. Its thermal fatigue resistance and oxidation resistance make it ideal for combined cycle power plants operating at increasingly elevated temperatures.

Ultra-Supercritical Power Plants – To improve thermal efficiency and reduce CO₂ emissions, ultra-supercritical power plants require materials capable of withstanding steam temperatures above 700°C. Inconel 617 is used for superheater and reheater tubing in these advanced coal-fired power plants.

Aerospace Propulsion – The alloy is used in jet engine combustion chamber liners, afterburner components, tail nozzle liners, thrust reversers, and rocket engine thrust chambers. Its ability to withstand the extreme thermal and mechanical stresses of aerospace propulsion systems makes it the material of choice for high-performance aircraft.

Petrochemical Processing – Inconel 617 is used in ethylene cracking furnace radiant tubes, reformer tubes, pyrolysis furnaces, and high-temperature chemical reactors. Its outstanding resistance to carburization significantly extends tube life in ethylene production facilities, where carbon steel tubes may fail within months.

Industrial Furnace Manufacturing – The alloy is used for furnace hardware, radiant tubes, muffles, retorts, hearth plates, roller rails, and thermocouple protection tubes. Its high-temperature strength and oxidation resistance make it suitable for heat treating equipment operating at temperatures above 1000°C.

Waste Incineration and Environmental – Inconel 617 is used in waste incineration plants, biomass power generation, and pollution control equipment. Its resistance to chloride and sulfide corrosion at elevated temperatures makes it valuable in high-temperature garbage incineration environments.

Standards & Specifications

Product Form	ASTM Standard	ASME Standard	AMS Standard
Seamless Pipe/Tube	ASTM B167	ASME SB-167	—
Welded Pipe	ASTM B517, ASTM B516	ASME SB-517, SB-516	—
Bar/Rod	ASTM B166	ASME SB-166	AMS 5887
Plate/Sheet/Strip	ASTM B168	ASME SB-168	AMS 5888, AMS 5889
Forgings	ASTM B564	ASME SB-564	AMS 5887
Fittings	ASTM B366	ASME SB-366	—
UNS Designation	N06617
Werkstoff Number	2.4663
DIN Designation	NiCr22Co12Mo9
GB/T Equivalent	NiCr22Co12Mo9

Frequently Asked Questions

Q: What is the maximum service temperature for Inconel 617?

A: Inconel 617 is rated for continuous service up to 1150°C (2100°F) for oxidation resistance. For structural strength, recommended maximum continuous service is approximately 1000°C (1830°F). The alloy is particularly suitable for service in the 800-1100°C range where few other alloys maintain their properties.

Q: What is the main difference between Inconel 617 and Inconel 625?

A: Inconel 617 contains cobalt (10-15%) and higher aluminum (0.8-1.5%), providing superior high-temperature strength and oxidation resistance at temperatures above 1000°C. Inconel 625 contains niobium (3.15-4.15%) and is optimized for corrosion resistance at lower temperatures (up to 982°C). Choose 617 for extreme high-temperature applications; choose 625 for corrosion resistance in marine and chemical environments.

Q: Is Inconel 617 readily weldable?

A: Yes, Inconel 617 has good weldability using GTAW, GMAW, and SMAW processes. Use matching filler metal (ERNiCrCoMo-1), control interpass temperature ≤150°C, and use low heat input. Preheating is generally not required, but post-weld heat treatment may be needed for heavy sections.

Q: What is the Chinese equivalent of Inconel 617?

A: The Chinese standard equivalent is NiCr22Co12Mo9 (GB/T 14992-2005). The alloy is also commonly referenced by its UNS designation N06617 in international specifications.

Q: What product forms are available for Inconel 617?

A: Womic Steel supplies Inconel 617 in seamless pipe, welded pipe, steel bar, steel plate, steel coil, strip, flanges, pipe fittings, forgings, wire, and valves. Complete product specifications and size ranges are listed in the product availability section.

Q: What are the primary applications for Inconel 617?

A: The alloy is used in advanced nuclear reactors (VHTR, MSR), gas turbine combustion chambers, ultra-supercritical power plants, aerospace propulsion systems, petrochemical reformers, ethylene cracking furnaces, and industrial furnace components.

Q: Does Inconel 617 require heat treatment?

A: Yes, solution annealing at 1150-1200°C followed by water quenching is recommended to achieve optimal microstructure and creep resistance. For thickness below 1.5mm, rapid air cooling may be acceptable.

Contact Womic Steel

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E-mail: sales@womicsteel.com

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Womic Steel – Your reliable partner for Inconel 617 (UNS N06617) seamless pipe, welded pipe, steel bar, steel plate, steel coil, flanges, fittings, forgings, and valves for advanced nuclear reactors, gas turbine power generation, aerospace propulsion, and ultra-high-temperature petrochemical applications worldwide. Full traceability, classification society certification, and EN 10204 Type 3.1/3.2 documentation available.