Everything you need to know about manufacturing with Inconel alloys—from grade selection to finished component delivery.
Inconel is a family of nickel-chromium superalloys developed by Special Metals Corporation, renowned for their exceptional performance in extreme environments. These alloys resist oxidation and corrosion at high temperatures while maintaining excellent mechanical strength—properties that have made them essential materials in aerospace gas turbines, nuclear reactors, chemical processing, oil and gas extraction, and marine engineering. CastAlloy provides comprehensive Inconel manufacturing services encompassing vacuum investment casting, hot forging, isothermal forging, and precision CNC machining across all major Inconel grades.
The most widely used Inconel grades are Inconel 718 and Inconel 625, which together account for the vast majority of Inconel consumption worldwide. Inconel 718 alone represents approximately 30 percent of all superalloy production, making it the single most important superalloy in commercial use. These alloys achieve their performance through fundamentally different strengthening mechanisms, giving each distinct advantages for specific applications.
Inconel 718 (UNS N07718) is a precipitation-hardened nickel-chromium alloy that achieves its exceptional properties through the formation of gamma-prime (Ni3(Al,Ti)) and gamma-double-prime (Ni3Nb) strengthening phases during aging heat treatment. This dual-phase strengthening produces tensile strengths exceeding 180 ksi with yield strengths above 150 ksi in the fully aged condition. The alloy maintains useful strength up to approximately 1,300 degrees Fahrenheit (704 degrees Celsius), above which the strengthening precipitates begin to dissolve and over-age.
What makes Inconel 718 uniquely valuable is its combination of high strength with excellent fabricability. Unlike many precipitation-hardened superalloys that are susceptible to strain-age cracking during welding, Inconel 718's slow precipitation kinetics allow it to be welded, formed, and heat treated with relatively conventional equipment and procedures. This weldability, combined with good forgeability across a workable temperature window of 1,700 to 2,050 degrees Fahrenheit, makes Inconel 718 the most versatile superalloy available for a broad range of manufacturing processes including investment casting, hot forging, and CNC machining.
Primary applications for Inconel 718 include gas turbine discs and shafts (where its high fatigue strength under rotating loads is critical), aerospace structural fasteners (combining high strength with corrosion resistance at moderate temperatures), compressor blades, rocket engine components, nuclear reactor springs and bolting, cryogenic storage tanks (the alloy retains excellent toughness at cryogenic temperatures), and oil and gas wellhead equipment.
Inconel 625 (UNS N06625) takes a fundamentally different approach to achieving high performance. Rather than relying on precipitation hardening, it is solid-solution strengthened by its high molybdenum (8 to 10 percent) and niobium (3.15 to 4.15 percent) content dissolved in the nickel-chromium matrix. This produces lower maximum strength than Inconel 718 (tensile of 120 to 150 ksi versus 180+ ksi) but delivers superior corrosion resistance across a much broader range of aggressive environments.
Inconel 625's high molybdenum content provides exceptional resistance to pitting and crevice corrosion in chloride-bearing environments, including seawater, brackish water, and chloride-contaminated process streams. The alloy resists stress corrosion cracking in chloride environments where many stainless steels and even some nickel alloys fail. It also offers excellent resistance to a wide range of organic and inorganic acids, alkalis, and salt solutions, making it one of the most versatile corrosion-resistant alloys available.
Key applications for Inconel 625 include subsea oil and gas equipment (flowlines, risers, connectors, and manifold components exposed to sour service conditions), chemical processing vessels and piping (handling mixed acid environments), marine engineering (propeller blades, submarine exhaust systems, seawater-cooled heat exchangers), flue gas desulfurization systems, aerospace exhaust and thrust reverser components, and nuclear waste processing equipment.
Inconel 713C is a cast-only nickel-based superalloy optimized for maximum creep resistance at elevated temperatures. Its composition includes high aluminum and titanium content for strong gamma-prime precipitation, producing excellent stress-rupture properties up to approximately 1,900 degrees Fahrenheit. Because its high gamma-prime volume fraction makes it too brittle for forging, components are exclusively manufactured through investment casting. Primary applications include turbine wheels, integral turbine rotors (blisks), and other non-rotating hot-section gas turbine components.
Inconel 600 (UNS N06600) is a solid-solution strengthened nickel-chromium alloy with excellent resistance to high-temperature oxidation and carburization. Its 72 percent minimum nickel content provides resistance to chloride-ion stress corrosion cracking, while 14 to 17 percent chromium ensures oxidation resistance. Inconel 600 is widely used in furnace hardware, heat treating equipment, chemical processing vessels, and nuclear steam generator tubing.
Inconel 601 builds on Inconel 600's composition with the addition of aluminum (1.0 to 1.7 percent) to form a protective alumina scale that dramatically improves high-temperature oxidation resistance. This makes it the preferred choice for thermal processing equipment, radiant tubes, furnace muffles, and combustion chamber linings operating at temperatures up to 2,200 degrees Fahrenheit.
Inconel X-750 is a precipitation-hardenable alloy that maintains good strength and corrosion resistance up to 1,300 degrees Fahrenheit. Its gamma-prime strengthening provides excellent relaxation resistance, making it the standard material for high-temperature springs, bolts, and fasteners in gas turbines and nuclear reactors where maintaining bolt preload at elevated temperature is critical.
Inconel 690 offers enhanced resistance to stress corrosion cracking compared to Inconel 600, achieved through its higher chromium content (27 to 31 percent). It has largely replaced Inconel 600 as the standard material for nuclear steam generator tubing in pressurized water reactors, where long-term resistance to primary water stress corrosion cracking is essential for plant safety and reliability.
| Grade | UNS | Strengthening | Tensile (ksi) | Max Temp | Key Advantage |
|---|---|---|---|---|---|
| Inconel 718 | N07718 | Precipitation | 180+ | ~1,300°F | Highest strength + weldability |
| Inconel 625 | N06625 | Solid solution | 120-150 | ~1,800°F | Broadest corrosion resistance |
| Inconel 713C | N07713 | Precipitation (cast) | 110-130 | ~1,900°F | Maximum creep resistance |
| Inconel 600 | N06600 | Solid solution | 80-100 | ~2,000°F | Oxidation + SCC resistance |
| Inconel 601 | N06601 | Solid solution | 80-100 | ~2,200°F | Best high-temp oxidation |
| Inconel X-750 | N07750 | Precipitation | 140-170 | ~1,300°F | Relaxation resistance (springs) |
| Inconel 690 | N06690 | Solid solution | 85-100 | ~1,800°F | Nuclear SCC resistance |
CastAlloy provides comprehensive Inconel manufacturing services encompassing the full range of processes needed to transform raw Inconel alloys into finished, inspected components ready for service. Our capabilities are specifically designed for the unique challenges these alloys present during manufacturing.
Investment Casting: Our vacuum induction melting (VIM) capability prevents oxide contamination during melting and pouring of Inconel alloys. The investment casting process produces near-net-shape components with complex internal passages, thin walls down to 0.030 inches, and intricate geometries. We cast all major Inconel grades with component weights from a few grams to nearly one metric ton. Post-casting hot isostatic pressing eliminates microporosity, and heat treatment per AMS or customer specifications optimizes mechanical properties.
Forging: Our forging presses with capacities from 800 to over 2,000 metric tons shape Inconel billets into high-integrity components with refined grain structures. Forged Inconel parts deliver 20 to 40 percent higher fatigue strength than cast equivalents, making forging the required process for turbine discs, shafts, and other rotating or fatigue-critical components. We offer open-die, closed-die, and isothermal forging with precise temperature control through medium-frequency induction heating.
CNC Machining: Inconel is notoriously difficult to machine due to high cutting forces, rapid work hardening, low thermal conductivity, and aggressive tool wear. Our CNC machining centers are equipped with high-pressure through-spindle coolant (1,000+ PSI), ceramic and CBN tooling, and optimized cutting strategies that our engineering team has refined through decades of production experience on Inconel alloys. We achieve tolerances as tight as plus or minus 0.0005 inches with surface finishes down to 16 Ra microinches.
Selecting the right Inconel grade requires matching alloy properties to the specific operating conditions of your application. Here is a decision framework our metallurgical team uses when advising customers:
If maximum mechanical strength is the primary requirement (up to approximately 1,300 degrees Fahrenheit service temperature), Inconel 718 is almost always the best choice. Its combination of 180+ ksi tensile strength, excellent fatigue properties, and good fabricability makes it the default selection for structural and rotating components.
If corrosion resistance is the dominant concern, particularly in chloride-bearing environments, seawater, or reducing acid conditions, Inconel 625 provides the broadest corrosion resistance of any commercial nickel alloy. It is the standard material for subsea equipment, chemical processing, and marine applications.
If the application involves very high temperatures (above 1,800 degrees Fahrenheit) in oxidizing conditions, Inconel 600 or 601 should be considered. Inconel 601's alumina-forming capability makes it particularly suited for thermal processing and furnace applications.
If creep resistance at extreme temperature is critical and the component geometry can be produced by casting, Inconel 713C provides the best stress-rupture properties among Inconel grades. For a more detailed comparison, see our Inconel 718 vs 625 guide and Superalloy Selection Guide.
Our engineering team is available for no-cost material selection consultations. Contact CastAlloy to discuss your specific application requirements and get expert guidance on the optimal Inconel grade and manufacturing process.
Proper heat treatment is essential for achieving the intended properties of each Inconel grade. For Inconel 718, the standard aerospace heat treatment per AMS 5663 consists of solution treatment at 1,750 degrees Fahrenheit for one hour followed by air cooling, then a two-step aging sequence: first age at 1,325 degrees Fahrenheit for eight hours, furnace cool to 1,150 degrees Fahrenheit, then hold at 1,150 degrees Fahrenheit for a total aging time of eighteen hours before air cooling. This produces the optimal distribution of gamma-prime and gamma-double-prime strengthening precipitates. Alternative heat treatments are available to optimize specific properties; for example, higher solution temperatures produce larger grain sizes that improve stress-rupture and creep performance at the expense of tensile and fatigue strength.
Inconel 625 is typically supplied in the solution-annealed condition (annealed at 1,900 to 2,100 degrees Fahrenheit and rapid cooled). Unlike Inconel 718, no aging treatment is required because Inconel 625 derives its strength from solid-solution strengthening rather than precipitation hardening. However, extended exposure to temperatures between 1,100 and 1,600 degrees Fahrenheit during service can cause precipitation of Ni3Nb and other phases that increase strength but reduce ductility and corrosion resistance. This must be considered when selecting Inconel 625 for applications involving long-term intermediate-temperature exposure.
Weldability varies significantly among Inconel grades and is often a decisive factor in alloy selection. Inconel 718 offers the best weldability among the precipitation-hardened superalloys because its primary strengthening phase (gamma-double-prime) precipitates slowly enough to avoid strain-age cracking during post-weld heat treatment. Standard welding processes including gas tungsten arc welding (GTAW/TIG), gas metal arc welding (GMAW/MIG), electron beam welding, and laser welding are all applicable. Inconel 625 is even more weldable due to its solid-solution strengthened nature, and Inconel 625 filler metal is widely used as a universal filler for welding dissimilar nickel alloys and for overlay cladding of carbon steel equipment. Inconel 713C, conversely, is essentially unweldable due to its high gamma-prime volume fraction, which is why it is exclusively used in the as-cast condition.
Engineers frequently evaluate Inconel against competing alloy families when specifying components for high-temperature or corrosive-service applications. Compared to austenitic stainless steels (304, 316, 321), Inconel alloys offer dramatically better performance at temperatures above 1,000 degrees Fahrenheit, with superior resistance to chloride stress corrosion cracking and substantially higher strength. The trade-off is cost: Inconel typically costs four to ten times more than stainless steel per pound, so engineers should specify Inconel only where stainless steel cannot meet the performance requirements.
Compared to Hastelloy alloys, the Inconel family offers broadly similar performance in many environments. The primary differentiation is that Hastelloy C-type alloys (C-276, C-22, C-2000) provide superior resistance to reducing acid environments (hydrochloric, sulfuric, phosphoric acids) and wet chlorine gas, while Inconel alloys excel in high-temperature structural applications where mechanical strength is as important as corrosion resistance. For a detailed comparison of the two most popular Inconel grades, see our Inconel 718 vs 625 comparison guide, and for broader alloy selection guidance, consult our Superalloy Selection Guide.
Inconel alloys carry significant material cost premiums reflecting their high nickel content (50 to 72 percent), strategic alloying elements (molybdenum, niobium, chromium), and the specialized melting practices required for production. Inconel 718 is the most widely available grade due to its enormous production volume, with raw material costs typically in the range of thirty to sixty dollars per pound depending on product form, specification, and market conditions. Inconel 625 commands a premium over 718 due to its higher molybdenum content (8 to 10 percent Mo versus 3 percent Mo in 718). Less common grades like Inconel 713C and X-750 may have longer lead times and minimum order quantities.
CastAlloy maintains strategic raw material sourcing relationships with major Inconel producers to ensure competitive pricing and reliable supply. Our near-net-shape manufacturing processes (investment casting and closed-die forging) minimize material waste, which is particularly valuable when working with materials costing fifty dollars or more per pound. For price-sensitive applications, our engineering team can evaluate whether a less expensive alloy (such as A-286 or duplex stainless steel) might meet the performance requirements at lower cost.
Inconel alloys serve some of the most demanding applications in modern engineering. In aerospace gas turbines, Inconel 718 turbine discs rotate at speeds exceeding 10,000 RPM while enduring temperatures above 1,000 degrees Fahrenheit and centrifugal stresses measured in thousands of pounds per square inch. The consequences of disc failure are catastrophic, which is why forged Inconel 718 is universally specified for this application and every disc is subjected to ultrasonic inspection, fluorescent penetrant inspection, and mechanical property verification before entering service.
In the offshore oil and gas industry, Inconel 625 serves as the standard material for subsea wellhead connectors, flowline components, and manifold systems that must resist the combined effects of seawater exposure, hydrogen sulfide from sour gas, temperatures ranging from near-freezing seabed conditions to several hundred degrees at downhole depth, and mechanical loads from wave action, current, and internal pressure. These components must operate reliably for 20 to 30 years with zero maintenance access, making material reliability literally a matter of environmental safety.
In nuclear power plants, Inconel 690 steam generator tubing provides the critical pressure boundary between radioactive primary coolant and non-radioactive secondary systems. The tubing must resist stress corrosion cracking in high-temperature primary water containing dissolved hydrogen for the entire 40 to 60 year plant operating lifetime. Inconel 690's superior resistance to primary water stress corrosion cracking compared to the original Inconel 600 tubing has been a major factor in improving nuclear plant reliability and safety worldwide.
The growing small modular reactor (SMR) market represents an expanding application for Inconel alloys in heat exchangers, reactor vessel internals, and steam generators where the combination of high-temperature performance, corrosion resistance, and nuclear-grade quality are essential. CastAlloy is positioned to serve this emerging market through our established superalloy manufacturing capabilities and nuclear-compatible quality systems.
Inconel 718 is precipitation-hardened with tensile strength exceeding 180 ksi, making it ideal for high-strength structural and rotating components up to 1,300 degrees Fahrenheit. Inconel 625 is solid-solution strengthened with lower maximum strength (120 to 150 ksi) but superior corrosion resistance, especially in chloride-bearing environments, seawater, and reducing acids. Choose 718 when strength is the primary requirement; choose 625 when corrosion resistance dominates. For a detailed comparison, see our Inconel 718 vs 625 guide.
Weldability varies by grade. Inconel 625 has excellent weldability and its filler metal is widely used as a universal nickel alloy filler. Inconel 718 has good weldability for a precipitation-hardened superalloy due to its slow aging kinetics. Inconel 600 and 601 are readily weldable. Inconel 713C is essentially unweldable due to its high gamma-prime content and is used exclusively in the as-cast condition. CastAlloy can advise on the best welding procedures for your specific Inconel grade and application.
Inconel's cost reflects its high nickel content (50 to 72 percent), strategic alloying elements (molybdenum, niobium, chromium), the energy-intensive vacuum melting processes required for production, and the challenging manufacturing characteristics that require specialized equipment and expertise for casting, forging, and machining. However, the total cost of ownership is often favorable because Inconel components last dramatically longer than alternatives in aggressive environments, reducing replacement frequency, maintenance downtime, and safety risk. CastAlloy's near-net-shape manufacturing processes minimize material waste to help control costs.
Maximum service temperature varies by grade. Inconel 718 maintains useful strength up to approximately 1,300 degrees Fahrenheit. Inconel 625 serves up to approximately 1,800 degrees Fahrenheit. Inconel 600 operates up to about 2,000 degrees Fahrenheit. Inconel 601, with its alumina-forming capability, provides the best oxidation resistance up to approximately 2,200 degrees Fahrenheit. The specific temperature limit depends on the combination of mechanical loading, time at temperature, and environmental conditions in your application.
Yes, every Inconel component ships with complete documentation including material test reports (MTR) with chemical composition and mechanical properties, certificates of conformance (CoC), applicable NDT reports (X-ray, FPI, ultrasonic), dimensional inspection reports, and heat treatment records. Full material traceability from raw material mill certification through final inspection is maintained under our ISO 9001:2015 quality management system.
Vacuum investment casting of all Inconel grades
→Hot and isothermal forging of Inconel 718, 625, and more
→Dedicated Inconel 718 forging capabilities
→Expert CNC machining of Inconel 718
→Corrosion-resistant Inconel 625 forgings
→Precision machining of Inconel 625
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