Haynes Alloy 25 (Udimet L605 / UNS R30605) Cobalt Alloy Forgings | China Manufacturer

What Is Haynes Alloy 25 (L605)? — Material Overview & main Properties

Jiangsu Liangyi, a top ISO 9001:2015 certified China Haynes Alloy 25 manufacturer strategically located in Jiangyin, Jiangsu Province, specializes in producing high-quality Udimet L605 forged parts, Alloy L-605 open die forgings, and AMS 5759 cobalt alloy parts. With over 25 years of specialized forging experience and a global customer base spanning more than 50 countries, we deliver premium UNS R30605 Cobalt Alloy 25 products that meet the strictest international standards.

Haynes Alloy 25 , also known as Udimet L605, Alloy L-605, AMS 5759 or UNS R30605, is a non‑magnetic, wrought cobalt‑chromium‑tungsten‑nickel superalloy, strengthened mainly by solid‑solution hardening.Its tungsten content of 14–16% is the main strengthening element at high temperatures, while chromium at 19–21% delivers excellent oxidation and corrosion resistance, making it the best material choice for harsh service conditions. Unlike many other superalloys, Haynes 25 is not age‑hardenable. Its performance comes entirely from its chemical composition and thermomechanical processing. This gives it stable and consistent mechanical properties over a wide temperature range, with no risk of degradation from over‑aging.

 Haynes 25 retains excellent tensile and yield strength up to 2150°F (1176°C) and provides excellent oxidation resistance up to 1900°F (1038°C). This combination of properties cannot be reached by conventional austenitic stainless steels, low‑alloy steels, or even many nickel‑based superalloys at the same temperatures.The cobalt base also gives Haynes 25 naturally better wear and galling resistance than nickel‑based alloys. This is a main advantage for rotating turbine parts, bearing races and valve seats that face surface contact pressure during operation.

Additionally, Cobalt Alloy 25 exhibits outstanding corrosion resistance across a wide range of chemically aggressive environments, including resistance to oxidizing mineral acids at moderate concentrations, wet chlorine at ambient conditions, and sulfur-bearing combustion gases at elevated temperatures. Detailed corrosion resistance data by specific environment is provided in the Corrosion & Oxidation Resistance section below.

Why Choose Jiangsu Liangyi as Your L605 Forging Supplier

As a trusted Jiangsu L605 forging supplier with deep expertise in cobalt-based superalloys, we offer unmatched quality, reliability, and customer service for all your Haynes Alloy 25 requirements:

Available Haynes Alloy 25 Forged Product Shapes & Sizes

Our Jiangyin Cobalt Alloy 25 forging factory produces a full range of L605 forged products in all kinds of standard and custom shapes and sizes:

Industrial Applications of L605 Cobalt Alloy Forgings

 Haynes Alloy 25 forgings are preferred over other superalloys when designers need a material that combines non‑magnetic properties, thermal stability above 900°C, hot gas corrosion resistance, and consistent long‑term strength without the complexity of precipitation hardening. These key application areas directly leverage these advantages:

Aerospace & Defense

Aerospace is still the largest user of Haynes Alloy 25 forgings. The alloy’s non‑magnetic property is essential for parts near navigation and guidance systems, while its oxidation resistance in combustion environments enables thin‑section designs that cannot be achieved with heavier or lower‑performance alloys.

• Military and commercial gas turbine engine combustion chambers (inner and outer liners)
• Afterburner parts: flame holders, mixing rings, and thrust augmentor hardware
• Turbine support rings, transition ducts, and hot-section structural frames
• Turbine vanes and nozzle guide vane rings for both axial and centrifugal designs
• High-temperature fasteners: bolts, studs, and nuts for engine casing joints (>800°C service)
• Structural parts for hypersonic vehicle leading edges and control surfaces

Power Generation

In both gas turbine power plants and steam turbine stations, L605 parts must withstand tens of thousands of operating hours under cyclic thermal and mechanical loading. The alloy has resistance to thermal fatigue cracking and predictable creep behavior ,making it the best material choice for long-life power generation parts.

• Gas and steam turbine blades, disks, and impellers (stages 1–3, high-temperature zones)
• Turbine blisks, diaphragms, and first-stage nozzles
• Steam turbine control reheat valve discs, spindles, and stems (CRV / RSV)
• MSV/GV/CV/CRV valve seats, cores, and sleeves for main steam and reheat circuits
• Main steam valve covers, bonnets, and upper casings (>550°C steam service)
• Turbine guide rings, seal rings, and rotor end rings
• High-temperature expansion joint rings and bellows flanges

Industrial & Process Manufacturing

• High-temperature ball bearings and bearing races where magnetic-neutral behavior is needed.
• Gas compressor stationary vane rings and impeller shroud rings
• Double-headed studs, bolts, and nuts for pressure vessel flanges at elevated temperature
• Chemical processing reactor internals (agitators, baffles, stirrer shafts) in hot oxidizing media
• Heat treatment fixtures, baskets, and furnace conveyor parts (>1000°C furnace environments)
• Glass fiber production spinning tips and bushing plates

Oil & Gas

• High-pressure, high-temperature (HPHT) wellhead Christmas tree components and valve bodies
• Corrosion-resistant valve trim parts (seats, balls, stems) for sour gas (H₂S) service
• Downhole tool mandrels and flow control components in HPHT well completions
• Subsea equipment parts exposed to chloride environments at elevated temperatures

Marine

• Ship propulsion gas turbine combustion parts and exhaust rings
• Marine engine exhaust valves and valve seats for heavy fuel oil service
• Naval propulsion system structural rings in non-magnetic applications

Manufacturing Process for Haynes Alloy 25 Forgings

Producing high-quality Haynes Alloy 25 forgings is far more demanding than manufacturing conventional stainless steels or low-alloy steels.L605’s high tungsten content (14–16%) greatly increases its flow resistance during hot forming, requiring larger forging press capacities, stricter temperature control, and more precise die design than similar nickel-based superalloys.The process sequence below shows our proven and validated production method for AMS 5759 cobalt alloy forgings.

Step 1 — Premium Double-Melting Process

The starting point for all our Haynes Alloy 25 forgings is double-melted ingot stock, produced by one of two proven routes:

• VIM/ESR — Vacuum Induction Melting followed by Electro-Slag Re-melting: the preferred route for the largest ring forgings and heavy-section bars where maximum cleanliness and segregation control are needed.
• VIM/VAR — Vacuum Induction Melting followed by Vacuum Arc Re-melting: used where the tightest control over oxygen and nitrogen content is specified, as is common in important aerospace applications.

Both routes guarantee a non-metallic inclusion content well below the limits that would be achievable with single-melt processing. This directly translates into superior fatigue life, reproducible mechanical properties, and reliable ultrasonic testing (UT) inspectability in the finished forging.

Step 2 — Controlled Hot Working & Open Die Forging

We heat L605 ingots to the forging temperature range — usually 1093°C to 1204°C (2000°F to 2200°F) — and shape them using our 2000–6300 ton hydraulic presses. The main goal at this step is to reach a minimum forging ratio of 3:1 (reducing the cross-sectional area) to fully break down the original cast structure and create a consistent, fine-grained forged matrix. For important rotating parts, we regularly achieve forging ratios of 5:1 to 7:1, which makes the material much better at bending without breaking and more resistant to fatigue crack initiation, compared to material that’s only lightly forged. We monitor the hot working temperature using calibrated contact thermometers and infrared thermal cameras at multiple points during each press movement. If the surface temperature drops below 982°C (1800°F), we stop forging and put the piece back in the furnace. This prevents forging at temperatures where the metal doesn’t fully recrystallize — which would leave a mixed structure of large and small grains that harms the material’s fatigue performance.

Step 3 — Seamless Ring Rolling

For seamless rolled ring production, pierced blanks are rolled on our 1–5 meter diameter radial-axial ring rolling machines. The ring rolling process adds extra shaping around the ring’s circumference, further refining the grain structure and directing the metal flow to follow the ring’s circular direction — the main direction stress acts in most turbine ring parts. This gives stronger mechanical properties in the key load direction compared to rings cut from solid material or machined discs.

Step 4 — Solution Annealing Heat Treatment

After forging, all Haynes Alloy 25 parts undergo the following standardized solution annealing heat treatment:

• Annealing temperature: 2150°F to 2250°F (1176°C to 1232°C)
• Hold time: determined by section thickness (minimum 1 hour, plus additional time per inch/25mm of section thickness)
• Quench: rapid air cooling or water quenching, depending on section size

This treatment dissolves any carbide deposits formed during cooling after forging, restores the fully recrystallized grain structure, and removes leftover forging stresses. The result is a consistent, fine-grained austenitic matrix with steady mechanical properties across the entire section, confirmed by structural tests on samples taken from test pieces forged at the same time as the production part.

Chemical Composition of Haynes Alloy 25 (UNS R30605 / AMS 5759)

The chemical composition limits below apply to Haynes Alloy 25 bars and forgings per AMS 5759 and UNS R30605. The "Role in Alloy" column explains the metallurgical function of each element — useful context for engineers performing failure analysis, weldability assessments, or alloy substitution evaluations:

Room-Temperature Mechanical Properties of Haynes Alloy 25 Forgings (AMS 5759)

The table below lists minimum guaranteed mechanical properties per AMS 5759 at room temperature (21°C / 70°F) in the annealed condition, alongside typical achieved values for reference. The AMS minimums represent the acceptance threshold; our production forgings consistently exceed these values.

Elevated-Temperature Mechanical Properties of Haynes Alloy 25 (L605)

The room-temperature values listed in AMS 5759 are the contractual minimums — but for design engineers working on gas turbine parts, the high-temperature strength data is what really determines material choice. The data below shows typical tensile properties at operating temperatures  for annealed Haynes Alloy 25 forgings. These are the important values when setting wall thicknesses, determining creep limits, or comparing L605 with other materials for a specific operating temperature.

Several patterns in this data are worth highlighting for designers unfamiliar with Haynes Alloy 25 behavior:

• Gradual, predictable strength reduction: Unlike precipitation-hardened alloys (e.g., Inconel 718) that experience a sharp strength drop at their overaging temperature, L605 shows a smooth, continuous decrease. This makes it easier to design with appropriate safety margins across a broad temperature range.
• Ductility recovery above 870°C: The elongation value, which decreases from ~62% at room temperature to a minimum of ~43% at 760°C, recovers to ~55–65% above 900°C. This increasing ductility at the highest temperatures is beneficial for resistance to thermal shock and thermal fatigue cracking.
• Useful strength above 1000°C: At 1093°C (2000°F) — a temperature that would render most stainless steels completely unserviceable — L605 still retains approximately 95 MPa UTS and 70 MPa yield strength. This is sufficient for lightly loaded structural parts in furnace or combustion applications.

Physical & Thermal Properties of Haynes Alloy 25 (L605 / UNS R30605)

The following physical and thermal properties are typical values for Haynes Alloy 25 in the annealed condition. These values are needed for thermal modeling, stress analysis, and heat exchanger design calculations. Note that all thermal properties are temperature-dependent; values at 871°C are included where available to illustrate the behavior at operating temperature:

Corrosion & Oxidation Resistance of Haynes Alloy 25 in Specific Environments

The corrosion resistance of Haynes Alloy 25 is very different from nickel-base corrosion-resistant alloys such as Hastelloy C276. While C276 is designed to resist reducing acid environments as much as possible, L605 is optimized for high-temperature corrosion, including high-temperature gas oxidation, sulfidation, and hot corrosion, rather than liquid corrosion at room temperature. Understanding this difference helps avoid costly mistakes in material selection.

High-Temperature Oxidation

Haynes Alloy 25 forms a dense, stable chromium oxide (Cr₂O₃) layer in air and combustion gases. This layer repairs itself and protects the material up to about 1038°C (1900°F) in continuous use. Above this temperature, the oxide layer grows faster and may flake off during repeated heating and cooling. That is why the safe maximum continuous service temperature is set at 1176°C (2150°F) — the annealing temperature — instead of the temperature where the oxide layer stays stable.Most austenitic stainless steels such as 304, 316 and 310 lose their protective oxide layer above 900°C, and Inconel 625 performs well only up to around 1000°C. L605 clearly offers better oxidation resistance in the 900°C–1100°C range.

Sulfidation Resistance

One often overlooked benefit of the cobalt base is better sulfidation resistance than nickel-base alloys. In sulfur-containing atmospheres, such as combustion gases from fuels with sulfur or refinery settings, cobalt-base alloys usually perform better than nickel-base alloys with similar chromium content. This is because cobalt sulfides are less stable and form more slowly than nickel sulfides. Haynes Alloy 25 shows good resistance to sulfidation damage at temperatures up to about 870°C (1600°F) under the sulfur levels found in normal combustion conditions.

Aqueous Corrosion — Environment-by-Environment Summary

Welding, Machining & Fabrication Guide for Haynes Alloy 25 (L605)

L605 is a difficult material to machine and form. Its high tungsten content and quick work-hardening trait need special tools, settings, and strict process control, which are very different from those used for stainless steels or nickel alloys. The advice below shows current best practices for making Haynes Alloy 25 / UNS R30605 parts:

International Standards Cross-Reference for Haynes Alloy 25 (L605)

Haynes Alloy 25 is recognized and specified under multiple national and international standards. The table below provides a comprehensive cross-reference to help procurement engineers, quality managers, and inspection bodies identify equivalent designations across different standards systems:

Haynes Alloy 25 vs. Other High-Temperature Alloys — Side-by-Side Comparison

The following comparison is intended for engineers evaluating Haynes Alloy 25 against other commonly specified superalloys for high-temperature forging applications. Values are typical for annealed/solution-treated wrought product unless otherwise noted:

Comprehensive Quality Inspection & Testing

To guarantee the highest quality standards for every UNS R30605 forged part, we perform a full range of inspection and testing procedures in our in-house quality control laboratory. All test procedures are carried out by trained and experienced quality personnel based on the applicable ASTM, AMS, and EN standards:

• Chemical analysis by optical emission spectrometry (OES) and wet chemistry cross-check
• Room-temperature mechanical property testing: tensile, bending, Charpy impact
• High-temperature tensile testing (upon customer request, up to 1000°C)
• Ultrasonic Testing (UT) per ASTM A388 / AMS 2630 — 100% volumetric inspection of all bars and forgings
• Magnetic Particle Inspection (MPI/MT) per ASTM E709 for surface and near-surface defect detection
• Liquid Penetrant Testing (PT) per ASTM E165 / AMS 2647 for surface crack detection
• Radiographic (X-Ray) testing per ASTM E1030 (upon customer request)
• Hardness measurement: Rockwell, Brinell, and Vickers methods as applicable to section size
• Metallographic cross-section examination: grain size per ASTM E112, microstructure, and inclusion rating
• Huey test (boiling 65% HNO₃ per ASTM A262 Practice C) for intergranular corrosion susceptibility
• 3D coordinate measuring machine (CMM) dimension test and GD&T verification
• Surface roughness (Ra) measurement per ISO 4287 / ASME B46.1
• Positive Material Identification (PMI/PAMI) by XRF or OES on 100% of finished parts

Minimum Order Quantity (MOQ), Packaging & Commercial Terms

The following commercial information applies to standard export orders for Haynes Alloy 25 / L605 / AMS 5759 forgings from Jiangsu Liangyi Co., Limited. All terms are subject to confirmation at the time of order placement and may vary for large-volume or long-term supply agreements:

Frequently Asked Questions (FAQ)