Inconel 625 vs Incoloy 825: Nickel-Alloy Comparison for Instrumentation Service
Inconel 625 (UNS N06625) and Incoloy 825 (UNS N08825) are two nickel-base corrosion-resistant alloys, and here they're compared head-to-head. The 625 grade carries higher strength and more molybdenum, a Ni-Cr-Mo-Nb alloy that resists chloride attack and pitting far better, with a PREN around 51. Alloy 825 costs less. It's a Ni-Fe-Cr-Mo-Cu alloy built for sulfuric and phosphoric acid service and general sour environments, with a PREN near 30. Pick 625 for the harshest chloride exposure, or when strength and high temperature matter most. Go with 825 where acid resistance at a lower price gets the job done. No matter how the pairing gets searched, as Inconel 625 vs 825, Incoloy 825 vs Inconel 625, alloy 625 vs alloy 825, or alloy 825 vs 625, it's the same question, answered both ways below. One clarification on names: on this page, "Inconel 825" refers to Incoloy 825 (UNS N08825). That's a common misnomer, since 825 is properly an Incoloy grade, not an Inconel one. And "625" refers to Alloy 625, or UNS N06625. Inconel® and Incoloy® are trademarks of Special Metals Corporation; Crestflo isn't affiliated with or endorsed by Special Metals.
Crestflo makes instrumentation tube fittings, valves and tubing in both alloys. That's not a theoretical point. One supplier can hand you either grade as a drop-in instrumentation component, complete with full traceability. Reviewed by the Crestflo Engineering Team.
Inconel 625 & Incoloy 825: Also Known As (UNS N06625, N08825, 2.4856, 2.4858)
Both alloys travel under a handful of names, and buyers order them under whatever term their supplier happens to use. Inconel 625 shows up as Alloy 625, UNS N06625, Werkstoff 2.4856, DIN NiCr22Mo9Nb, "grade 625", "nickel alloy 625", or the Ni-Cr-Mo-Nb alloy. Trade names multiply the list further: Nicrofer 6020, Chronin 625, Nickelvac 625, and Haynes 625 are all the same metal under different labels. Incoloy 825 has its own set of aliases: Alloy 825, UNS N08825, Werkstoff 2.4858, EN NiCr21Mo, "grade 825", "nickel alloy 825", the Ni-Fe-Cr-Mo-Cu alloy, and the trade name Nicrofer 4221. People also call it "Inconel 825," which isn't technically correct, though the habit persists across the industry. Whichever label you run into, "Inconel 825" and "Incoloy 825" name the same UNS N08825 alloy. For the full single-alloy data, check the complete datasheets for Inconel 625 (UNS N06625) and Incoloy 825 (UNS N08825).
At-a-Glance: Inconel 625 vs Incoloy 825 Comparison Table
| Attribute | Inconel 625 (UNS N06625) | Incoloy 825 (UNS N08825) |
|---|---|---|
| Alloy family | Ni-Cr-Mo-Nb, solid-solution strengthened | Ni-Fe-Cr-Mo-Cu-Ti, titanium-stabilized austenitic |
| UNS | N06625 | N08825 |
| Werkstoff / W.Nr. | 2.4856 | 2.4858 |
| Nickel (Ni) | ≥ 58% | 38–46% |
| Chromium (Cr) | 20.0–23.0% | 19.5–23.5% |
| Molybdenum (Mo) | 8.0–10.0% | 2.5–3.5% |
| Niobium+Tantalum (Nb+Ta) | 3.15–4.15% | — |
| Copper (Cu) | ≤ 0.5% (incidental) | 1.5–3.0% |
| Iron (Fe) | ≤ 5.0% | ≥ 22.0% (balance) |
| PREN (Cr + 3.3 × Mo) | ~47–56 (typically cited ~51) | ~28–35 (typically cited ~30) |
| Tensile strength (annealed, typ.) | ~827–1,034 MPa (120–150 ksi) | ~586–690 MPa (85–100 ksi) |
| 0.2% yield strength (annealed, typ.) | ~414–517 MPa (60–75 ksi) | ~241–345 MPa (35–50 ksi) |
| Elongation (typ.) | ~30–45% | ~30–45% |
| Hardness (annealed, typ.) | ≤ ~220 HB | ≤ ~180 HB |
| Density | ~8.44 g/cm³ | ~8.14 g/cm³ |
| Max continuous service temp | Very high, oxidation/creep resistant to ~980 °C regimes | Lower, Ti-stabilized against sensitization; not a high-creep alloy |
| Magnetic response | Non-magnetic (austenitic) | Non-magnetic (austenitic) |
| Machinability | Work-hardens; tougher to machine | More machinable than 625 |
| Weldability | Excellent (GTAW, ERNiCrMo-3 / 625 filler) | Good; matching filler |
| Sour service (NACE MR0175 / ISO 15156) | Qualified within limits | Qualified within limits |
| Relative raw-material cost | Higher (high Ni + Mo + Nb) | Lower (high Fe, lower Mo) |
These values reflect standard published alloy data, taken from the applicable Special Metals and ASTM ranges. They're customizable to whatever the requirement calls for. PREN itself is calculated as PREN = %Cr + 3.3 × %Mo; nickel alloys carry negligible nitrogen, so that term drops out. Alloy properties only, not Crestflo product ratings. For part pressure and temperature ratings, check the product pages.
Chemical Composition & Designations: N06625 vs N08825
Inconel 625 and Incoloy 825 perform differently because their chemistry is different at the core. Inconel 625 runs nickel-rich, at least 58% Ni, and its Ni-Cr-Mo-Nb makeup leans on high molybdenum (8–10%) and niobium (3.15–4.15%) to deliver both pitting resistance and solid-solution strength. Incoloy 825 takes a different path. It's a leaner, iron-bearing alloy (≥22% Fe) built on a Ni-Fe-Cr-Mo-Cu system, with less molybdenum (2.5–3.5%). What it lacks there, it makes up for with deliberate copper (1.5–3.0%) and titanium additions, tuned specifically for reducing acids and to guard against chloride stress-corrosion cracking and intergranular attack.
| Element | Inconel 625 (wt%) | Incoloy 825 (wt%) |
|---|---|---|
| Nickel (Ni) | ≥ 58 | 38–46 |
| Chromium (Cr) | 20.0–23.0 | 19.5–23.5 |
| Molybdenum (Mo) | 8.0–10.0 | 2.5–3.5 |
| Iron (Fe) | ≤ 5.0 | ≥ 22.0 (balance) |
| Niobium + Tantalum (Nb+Ta) | 3.15–4.15 | — |
| Copper (Cu) | ≤ 0.5 | 1.5–3.0 |
| Titanium (Ti) | ≤ 0.40 | 0.6–1.2 |
| Carbon (C, max) | 0.10 | 0.05 |
| Manganese (Mn, max) | 0.50 | 1.0 |
| Silicon (Si, max) | 0.50 | 0.5 |
Compositions follow the standard published ranges set out in the applicable specifications, with values drawn from the relevant standard and adjustable to requirement. In designation terms, 625 corresponds to UNS N06625 / W.Nr. 2.4856, known commercially as Nicrofer 6020, Chronin 625, and Haynes 625. 825, meanwhile, is UNS N08825 / W.Nr. 2.4858, sold under the name Nicrofer 4221. Comparing N06625 to N08825 is the precise way to tell the two alloys apart once trade names are set aside.
Corrosion Resistance: PREN, Chloride, Sour Service: Does Incoloy 825 Rust?
Carbon steel rusts. Neither of these alloys does, since both are corrosion-resistant austenitic nickel alloys, but they fend off corrosion by different mechanisms. Nickel alloys get scored using the Pitting Resistance Equivalent Number, or PREN, calculated as PREN = %Cr + 3.3 × %Mo, and that number splits the two apart sharply. Inconel 625 lands at roughly 47–56 (most sources cite a figure near 51). Incoloy 825 comes in well below that, at roughly 28–35 (commonly near 30). What explains the gap is molybdenum. Inconel 625 carries 8–10% Mo, and that's what gives it far greater resistance to chloride pitting, crevice corrosion and chloride stress-corrosion cracking than Incoloy 825 can manage with its 2.5–3.5% Mo.
| Metric | Inconel 625 | Incoloy 825 |
|---|---|---|
| PREN (Cr + 3.3 × Mo) | ~47–56 (typ. ~51) | ~28–35 (typ. ~30) |
| Chloride pitting resistance | Superior (high Mo) | Moderate |
| Crevice corrosion resistance | Superior | Moderate |
| Chloride SCC resistance | Very high | High (Ti-stabilized) |
| Sulfuric / phosphoric acid | Good | Superior (Cu addition) |
| Seawater / high chloride | Preferred | Limited |
| Sour service (NACE MR0175 / ISO 15156) | Qualified within limits | Qualified within limits |
Where chlorides, seawater or high-strength demands dominate the service, 625 is the stronger choice for corrosion resistance. Where reducing acids take over instead, sulfuric and phosphoric, 825's copper content gives it a real edge, and that's why it shows up so often in acid-handling and general sour-service work. Both alloys hold up in sour service and can be supplied to NACE MR0175 / ISO 15156. Still, check suitability against your actual H2S partial pressure, chloride level and temperature before committing. For cross-alloy context, the PREN comparison table is worth a look, as is the corrosion-by-media alloy selector from Crestflo.
Mechanical Strength & Temperature: Is Inconel 625 Stronger Than 825?
Yes, Inconel 625 is substantially stronger than Incoloy 825. Its annealed tensile strength (typically ~827–1,034 MPa / 120–150 ksi) and 0.2% yield (~414–517 MPa / 60–75 ksi) roughly double 825's numbers (~586–690 MPa tensile, ~241–345 MPa yield). That gap comes straight from 625's niobium-and-molybdenum solid-solution strengthening. Both alloys are non-magnetic austenitics, though, and both hold onto similarly high ductility, with elongation running around 30–45%.
| Property | Inconel 625 | Incoloy 825 |
|---|---|---|
| Tensile strength (annealed, typ.) | ~827–1,034 MPa (120–150 ksi) | ~586–690 MPa (85–100 ksi) |
| 0.2% yield strength (annealed, typ.) | ~414–517 MPa (60–75 ksi) | ~241–345 MPa (35–50 ksi) |
| Elongation (typ.) | ~30–45% | ~30–45% |
| Hardness (annealed, typ.) | ≤ ~220 HB | ≤ ~180 HB |
| Density | ~8.44 g/cm³ | ~8.14 g/cm³ |
| Max continuous service temp | ~980 °C regimes (oxidation/creep resistant) | Lower; not a high-creep alloy |
| Magnetic response | Non-magnetic | Non-magnetic |
When it comes to temperature, the two alloys split by role, not just by degree. Inconel 625 handles high heat well, with strong oxidation and creep resistance up to roughly 980 °C, making it the pick for elevated-temperature work and anything under fatigue load. Incoloy 825 gets its titanium stabilization to fight off sensitization and intergranular corrosion after heat exposure. It isn't built for high-creep, high-temperature duty, though. Its strength lies in corrosion resistance at moderate temperatures instead. Mechanical minimums follow the standard published values in the applicable ASTM product specification, and they can be adjusted to fit specific requirements.
Machinability & Weldability: Can Inconel 625 Be Welded? Is It Hard to Machine?
Welding isn't a problem for either alloy. Inconel 625 welds beautifully, usually by GTAW with matching ERNiCrMo-3 / 625 filler, and instrumentation work generally doesn't call for post-weld heat treatment. Incoloy 825 also welds well, again with matching filler. Machining tells a different story: 625 is the harder of the two to work, since it hardens fast under the tool and demands rigid setups, sharp tooling, and tightly controlled feeds and speeds. 825, by comparison, cuts more easily. None of that falls on the buyer, though. For instrumentation components, these fabrication details stay in-house.
When to Choose Inconel 625 vs Incoloy 825
It all hinges on one distinction: is the service driven by chloride and strength, or by acid and cost? Check the guide below first. Then confirm it holds up against your own conditions.
| Service condition | Recommended alloy | Why |
|---|---|---|
| Aggressive chloride / seawater | Inconel 625 | High Mo, PREN ~51 resists pitting/crevice |
| High strength / high pressure | Inconel 625 | ~2× the yield strength of 825 |
| Elevated temperature / creep / fatigue | Inconel 625 | Oxidation/creep resistant to ~980 °C |
| Sulfuric / phosphoric acid | Incoloy 825 | Copper addition aids reducing acids |
| General sour service, cost-sensitive | Incoloy 825 | Adequate corrosion at lower alloy cost |
| Severe H2S + chloride combined | Inconel 625 | Wider chloride/pitting margin |
As a rule of thumb, specify 625 when you're up against the most aggressive chloride exposure combined with high-strength and high-temperature duty. Reach for 825 where sulfuric or phosphoric-acid resistance is the priority and cost needs to stay down. Either way, confirm the choice against your actual H2S, chloride and temperature envelope before locking it in. For a workflow-driven pick, the sour-service alloy selection guide, the offshore / chloride selection guide and material selection by service walk through the logic. Curious how these nickel alloys compare with others? Hastelloy vs Inconel and Inconel vs Monel cover that ground. These alloys show up constantly in oil & gas, offshore and subsea work, and both grades are routinely specified for downhole tubing, chemical-injection lines and subsea umbilicals; surface instrumentation rounds things out.
Cost & Lead Time: Is Incoloy 825 Cheaper Than Inconel 625?
Yes, Incoloy 825 tends to be the cheaper alloy of the two. Inconel 625 packs in more nickel, plus more molybdenum and niobium, and that pushes its raw-material cost up. 825 runs cheaper thanks to its higher iron content and lower molybdenum. Exact pricing shifts with size, form and market conditions, so it's quoted per requirement rather than published outright. Anyone wanting lead-time, availability and post-tariff cost figures across alloys should check the alloy lead-time & cost benchmark. Crestflo's standard model is ready stock for standard items · made-to-order for specials · 6–8 week delivery, a real edge over the 20-plus-week lead times you'll typically see from the majors.
Standards & Product-Form Specs: ASTM B446, B443, B444, B425, B424, B423
Each alloy has its own family of ASTM product-form specifications. That matters if you're writing a spec that covers bar, sheet and tube.
| Product form | Inconel 625 (N06625) | Incoloy 825 (N08825) |
|---|---|---|
| Bar | ASTM B446 | ASTM B425 |
| Plate / sheet / strip | ASTM B443 | ASTM B424 |
| Seamless pipe / tube | ASTM B444 | ASTM B423 |
| Welded tube | ASTM B704 / B705 | ASTM B705 |
For sour service, both alloys are qualified under NACE MR0175 / ISO 15156 within their respective limits. Crestflo states conformance to the standard approvals applicable to each product type, for instrumentation compression fittings that anchor is ASTM F1387, while instrumentation valves qualify to ASME B16.34 and the applicable API standards. Certificates are held under our ISO 9001 / 14001 / 45001 & PED certification.
Both Alloys, One Supplier: Inconel 625 & Incoloy 825 Fittings, Valves & Tubing
Looking to source both 625 and 825 fittings from one supplier? Crestflo carries Inconel 625 and Incoloy 825, but only as instrumentation components. It isn't mill product. This is a material page, so it covers the grade broadly for general education. What Crestflo actually sells is narrower: instrumentation forms only. That covers compression and tube fittings, with end connections up to 2 inches (50 mm) OD, single or double ferrule, hardened or non-hardened. Instrumentation valves and instrumentation tubing round out the list.
| Form | Inconel 625 | Incoloy 825 |
|---|---|---|
| Tube fittings | 625 tube fittings | 825 tube fittings |
| Instrumentation valves | 625 valves | 825 valves |
| Tubing | 625 tubing | 825 tubing |
When you place an order, specify the alloy and UNS number, the size (imperial or metric), the end connection or thread, any NACE MR0175 requirement, and the MTC grade (3.1 standard, 3.2 on request). Compression tube fittings are tested to ASTM F1387 for dimensional interchange with major brands, so either alloy fits right into an existing Swagelok®, Parker® or Hy-Lok® tube-fitting layout. Needle, ball and check valves are available in both alloys too. For form details, check the full Inconel 625 material page and Incoloy 825 material page.
Why Crestflo for Inconel 625 & Incoloy 825 Instrumentation Parts
Crestflo is the instrumentation division of a four-decade-old, Government-of-India-recognized export house with a Middle-East delivery track record, heritage that backs a newer manufacturing brand. Compression tube fittings are qualified for dimensional interchange under ASTM F1387, so 625 or 825 parts drop into existing branded layouts. Every part is heat-number marked with EN 10204 3.1 MTC (3.2 on request) for full traceability, supplied in both imperial and metric sizes with hardened or non-hardened ferrules, PMI-verified, and NACE MR0175 / ISO 15156 compliant where specified. Origin is Indian; US / European melt is available on request, with full material traceability, see origin & compliance. Stock and delivery follow our standard model: ready stock for standard items · made-to-order for specials · 6–8 week delivery. We Engineer Confidence.
Need a quote on 625 or 825 parts? Request a quote, ask for a sample, or talk to an engineer directly. Coming over from another brand? Our engineering team will pull your Swagelok®/Parker® cross-reference for you.
Frequently Asked Questions: Inconel 625 vs 825
What is the main difference between Inconel 625 and Incoloy 825?
Inconel 625 sits at the higher end of the strength range among Ni-Cr-Mo-Nb alloys. It carries roughly 8–10% molybdenum and a PREN near 51, and it's built to handle aggressive chloride exposure along with demanding high-strength and high-temperature service. Incoloy 825, by contrast, costs less. This Ni-Fe-Cr-Mo-Cu alloy runs about 2.5–3.5% molybdenum with a PREN near 30. It's suited to sulfuric and phosphoric acid environments and general sour service.
Is "Inconel 825" the same as Incoloy 825?
Yes. People often say "Inconel 825," but that's not quite accurate. The correct designation is Incoloy 825, UNS N08825. Same grade, different label. Inconel® and Incoloy® are both trademarks of Special Metals Corporation.
Which alloy is better for sour gas or NACE MR0175 service?
Both alloys work in sour service, and both can be supplied to NACE MR0175 / ISO 15156. Inconel 625 tends to be the pick when chloride pitting and raw strength matter most. Incoloy 825 fits better when reducing-acid resistance is the priority and cost has to stay down. Don't finalize either one without checking your actual H2S levels, chloride content and temperature range.
Does Incoloy 825 rust?
No. Incoloy 825 is a corrosion-resistant austenitic Ni-Fe-Cr-Mo alloy, and it won't rust the way carbon steel does. That said, any alloy can corrode once you push it past its rated service window. Severe chloride environments, for instance, call for 625 instead.
Can Inconel 625 be welded?
Yes. Inconel 625 welds well, typically with GTAW and matching ERNiCrMo-3 / 625 filler, and most instrumentation work needs no post-weld heat treatment.
Is Inconel 625 hard to machine?
Inconel 625 work-hardens, and it's tougher to machine than 825. You need rigid setups, sharp tooling, and carefully controlled feeds and speeds. Incoloy 825, by contrast, machines more easily.
What is the PREN of 625 versus 825?
Inconel 625 and Incoloy 825 both use PREN = %Cr + 3.3 × %Mo, and nickel alloys carry next to no nitrogen, so that formula holds cleanly for both. Run the numbers and Inconel 625 lands around 47–56, with 51 the figure you'll see most often. Incoloy 825 comes in lower, roughly 28–35, typically cited near 30. The gap tells the real story: 625 resists pitting far better.
What are the equivalent designations for 625 and 825?
Inconel 625 is UNS N06625, also listed as Werkstoff 2.4856. Trade names for it include Nicrofer 6020, Chronin 625, and Haynes 625. Incoloy 825, meanwhile, corresponds to UNS N08825 and Werkstoff 2.4858, sold under the name Nicrofer 4221.
Which is more expensive, 625 or 825?
Inconel 625 usually costs more, since it packs in more nickel, molybdenum and niobium. Incoloy 825 runs cheaper thanks to its higher iron content and lower molybdenum. Actual prices shift with size, form and market conditions, so quotes get worked out per requirement.
What standards cover Inconel 625 and Incoloy 825?
Product forms follow different specs depending on the grade. For 625, that's ASTM B446 for bar, B443 for plate and sheet, and B444 for pipe and tube. With 825, the numbers shift: ASTM B425 covers bar, B424 covers plate and sheet, B423 covers tube. Both grades are qualified under NACE MR0175 / ISO 15156 for sour service, within their stated limits.
Does Crestflo supply both 625 and 825 fittings, valves and tubing?
Yes. Crestflo carries instrumentation compression and tube fittings up to 2" OD, along with valves and tubing in both alloys. Ferrules come hardened or non-hardened, buyer's choice. Fittings meet ASTM F1387 interchange, and every shipment ships with an EN 10204 3.1 MTC that includes heat-number traceability.
What lead time and origin apply to 625 and 825 components?
Standard items ship from ready stock, while specials are made to order; delivery runs 6–8 weeks either way. The framing's origin is Indian, though US or European melt is available on request, and full material traceability comes standard. TAA eligibility isn't overlooked, either. It's addressed on the origin and compliance page.