Project Description

Incoloy 825 / UNS N08825 is a nickel-iron-chromium solid-solution austenitic alloy with deliberate molybdenum, copper, and titanium additions. Engineered by Special Metals in the 1950s, it bridges the cost-performance gap between 300-series stainless steels and high-nickel CRA grades. Its defining characteristic is exceptional resistance to sulfuric and phosphoric acids — environments that destroy molybdenum-free stainless steels by uniform dissolution. With a PREN of approximately 31 and 38–46% nickel, it resists SCC in hot chloride media and retains good toughness from cryogenic temperatures to 540°C. SHUNFU METAL manufactures Incoloy 825 CRA pipe through EAF melting followed by VOD or AOD refining, ensuring ultra-low carbon ≤0.03% for optimum titanium stabilization. Every pipe undergoes 100% PMI, ultrasonic, eddy current, and hydrostatic testing before shipment.

Equivalent Grades of Incoloy 825 / N08825

Alloy UNS EN / DIN GB JIS ASTM Pipe PREN
Incoloy 825 N08825 2.4858 / NiCr21Mo NS142 NCF 825 B423 / B705 ~31
Alloy 625 N06625 2.4856 / NiCr22Mo9Nb NS3306 — B444 / B705 ~50
Alloy 31 N08031 1.4562 / X1NiCrMoCu32-28-7 NS1404 — B622 ~48
Alloy G-3 N06985 2.4619 / NiCr22Mo7Cu NS3403 — B622 ~43
Alloy 20Cb-3 N08020 2.4660 / NiCr20CuMo NS1403 — B729 / B464 ~29
Alloy 28 N08028 1.4563 / X1NiCrMoCu31-27-4 NS1401 — B668 ~38
Incoloy 825 N08825 CRA pipe
Incoloy 825 / N08825
CRA Seamless Pipe

Oil & Gas Applications of Incoloy 825 / N08825

Sour Gas Downhole Tubing

Production tubing and liner in H2S/CO2/chloride wells up to 149°C without elemental sulfur per NACE Table A.14 Type 4c.

Sand Screen Base Pipe

Precision slotted or wire-wrapped base pipe for downhole sand control in corrosive oil & gas completions.

Subsea & Surface Flowlines

Gathering and transport lines carrying sour multiphase production fluids from wellhead to processing facility.

Swell Packer Assemblies

Base mandrel and expansion sleeve for zonal isolation packers in open-hole and cased-hole sour completions.

Sulfuric Acid Alkylation

Reactor effluent coolers, acid transfer lines, and regeneration piping in refinery H2SO4 alkylation units.

Chemical Injection Lines

Downhole capillary injection tubing delivering corrosion inhibitors, scale dissolvers, and H2S scavengers.

Phosphoric Acid Evaporators

Heat exchanger tubes in wet-process H3PO4 concentration plants handling fluoride-contaminated acid.

Geothermal Production Casing

Production and injection casing strings in hot, CO2-charged geothermal brine wells.

FGD Scrubber Piping

Flue gas desulfurization absorber recirculation and quench piping exposed to dilute H2SO4/chloride condensate.

Incoloy 825 / N08825 Pipe Supply Range

SHUNFU METAL supplies Incoloy 825 CRA pipe and tube manufactured to ASTM B423, B705, B163, and API 5CRA / ISO 13680 Group 4 Category 21-42-3. Seamless pipe from OD 4 mm to 219 mm and welded pipe from OD 5 mm to 1219 mm, with wall thickness from 0.5 mm to 50 mm across SCH 5S through XXS. OCTG tubing and casing available from 2-1/16″ to 10-3/4″ OD with wall thickness up to 49 mm in lengths up to 21 m. All products certified to NACE MR0175 / ISO 15156 Table A.14 Type 4c for sour H2S service without temperature restriction below 132°C. Inspection per EN 10204 3.1 / 3.2 with optional 100% NDT, DPI, and third-party witness. End finishes: plain, beveled, threaded, or premium connections per API 5CT. SHUNFU validates each heat with OES + inert gas fusion chemistry, batch tensile and hardness testing, and ASTM G28 / A262 corrosion verification.

Chemical Composition of Incoloy 825 / N08825

Composition per ASTM B423 (wt%), with SHUNFU internal melt targets narrower than specification minimums.

Element Ni Cr Fe Mo Cu Ti Mn Si C Al S
Range 38.0–46.0 19.5–23.5 ≥22.0 2.5–3.5 1.5–3.0 0.6–1.2 ≤1.0 ≤0.5 ≤0.05 ≤0.2 ≤0.03

The alloy’s corrosion resistance derives from three synergistic mechanisms. Molybdenum (2.5–3.5%) and copper (1.5–3.0%) act in tandem against reducing sulfuric and phosphoric acids — Mo forms a passive MoO42− film while Cu raises the cathodic hydrogen overpotential, suppressing uniform dissolution that would destroy Mo-free grades. Titanium (0.6–1.2%) preferentially scavenges carbon as stable TiC precipitates, preventing grain-boundary chromium carbide sensitization during welding and slow cooling — the alloy remains immune to intergranular attack in the as-welded condition without post-weld heat treatment. High nickel (38–46%) suppresses chloride SCC by stabilizing the austenite matrix. SHUNFU maintains carbon at ≤0.03% internal target (spec ≤0.05%) to ensure full titanium stabilization with residual Ti:C ratio > 12:1, verified by OES and inert gas fusion analysis on every heat.

Mechanical Properties of Incoloy 825 / N08825

Incoloy 825 is supplied in the solution-annealed condition per ASTM B423 — it cannot be hardened by heat treatment but responds to cold work. SHUNFU anneals each batch at 927–1010°C followed by rapid water quenching to preserve the homogeneous austenitic structure.

Condition Tensile Strength (MPa) Yield Strength 0.2% (MPa) Elongation (%) Hardness
Hot-Finished Annealed (B423) ≥517 ≥172 ≥30 ≤90 HRB
Cold-Worked Annealed (B423) ≥586 ≥241 ≥30 ≤90 HRB
API 5CRA 110 ksi Grade 758–965 758–897 ≥11 ≤33 HRC
Cold Hardened (max typical) up to 1103 up to 1034 ≥8 ≤38 HRC

Physical constants (annealed, 20°C): Density 8.14 g/cm³ · Melting range 1370–1400°C · Elastic Modulus 195 GPa · Thermal conductivity 11.1 W/m·K · Poisson ratio 0.30 · CTE 14.0 μm/m·°C (20–500°C). Usable from cryogenic to 540°C (NACE limited to 149°C for sour service without elemental sulfur). At 200°C, yield strength retains approximately 85% of ambient value. SHUNFU verifies mechanical integrity through batch tensile testing on every heat treatment lot, Rockwell B / HRC hardness per ASTM E18 and E140, impact toughness per ASTM E23, and intergranular corrosion resistance per ASTM G28 Method A. Grain size is confirmed at ASTM 4–7 per E112 on every qualification test coupon.