Is Incoloy 825 a type of stainless steel?

No. Stainless steel is an iron-based alloy with a minimum of about 10.5% chromium. Incoloy 825 is a nickel-based superalloy with 50-55% nickel and iron as the balance.

What heat treatment do Incoloy 825 fasteners require?

Solution treatment at roughly 940-1010°C followed by a two-stage age: 8 hours at 718°C, furnace cool to 621°C, then a further 8 hours before air cooling.

Can Incoloy 825 fasteners be used at cryogenic temperatures?

Yes. Alloy 718 retains excellent toughness and ductility down to approximately -253°C (-423°F) with no ductile-to-brittle transition.

What sizes of Incoloy 825 fasteners do you manufacture?

Bolts and screws from M3 to M100 (3/16 inch to 4 inch), nuts and washers from M3 to M56 (3/16 inch to 2 inch), and lengths from 3 mm to 200 mm as standard. Larger diameters and non-standard lengths are produced to drawing.

Incoloy 825 Fasteners Manufacturer & Supplier in India — ASTM B425 / B564 UNS N08825 Bolts, Nuts, Stud Bolts and Washers

Q: What is the maximum temperature for Incoloy 825 fasteners?

Alloy 718 is rated for continuous service up to approximately 1300°F (704°C). It retains most of its strength to about 1200°F and can survive brief excursions higher, though the strengthening precipitate begins to coarsen and over-age above roughly 1350°F. For sustained service above 800°C, choose Inconel 600 or Inconel 601 instead.

Q: What is the difference between Incoloy 825 and Inconel 625 fasteners?

718 is precipitation-hardened and 625 is solid-solution strengthened. That makes 718 roughly twice as strong, but 625 works to a higher temperature and offers superior pitting and crevice resistance in seawater and acids.

Titanium-stabilised nickel-iron-chromium bolting engineered for sulphuric and phosphoric acid service, chloride stress-corrosion immunity and sour gas duty — supplied with full EN 10204 3.1 traceability from our Mumbai works.

ASTM B425 / B564

M3 to M100

40+ Fastener Types

7–15 Day Dispatch

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Why Incoloy 825 Is the Workhorse Alloy for Acid-Service Bolting

Most corrosion-resistant alloys are good at either oxidising or reducing conditions — rarely both. Incoloy 825 fasteners are specified precisely because they handle both. Known as Alloy 825, UNS N08825 and Werkstoff Nr. 2.4858, this titanium-stabilised nickel-iron-chromium alloy combines roughly 38–46% nickel for chloride stress-corrosion resistance, 19.5–23.5% chromium for oxidising media, 2.5–3.5% molybdenum for pitting and crevice resistance, and 1.5–3% copper for sulphuric and phosphoric acid duty. The titanium addition stabilises the grain boundaries against intergranular attack after welding. At Unifit Fastener, we manufacture the complete bolting family in Alloy 825 — hex bolts, heavy hex nuts, stud bolts, threaded rods, washers, screws and anchor fasteners — from M3 to M100 and 3/16" to 4", to ASTM B425, ASTM B564, ASME SB425 and ASTM F467/F468. Every lot is PMI-verified, hardness-checked and released with an EN 10204 3.1 mill test certificate. Whether you are bolting a pickling line, a phosphoric acid evaporator, a sour gas wellhead or an FGD absorber, you get the right metallurgy and documented traceability — the first time.

*Word count: 196 words.*

What Are Incoloy 825 Fasteners?

Incoloy 825 fasteners are threaded components machined, forged or cold-headed from a solid-solution-strengthened nickel-iron-chromium alloy. It is best understood as a heavily upgraded austenitic stainless steel: take 316L, roughly quadruple the nickel, add molybdenum, copper and a titanium stabiliser, and you arrive at 825. That composition is why it survives service streams that strip 300-series stainless steel fasteners within a single campaign.

The Metallurgy in Plain Engineering Terms

Nickel (38–46%) delivers resistance to chloride-ion stress corrosion cracking — the failure mode that most often removes 304 and 316 studs from coastal and brine service.
Chromium (19.5–23.5%) forms the passive oxide film that handles oxidising acids such as nitric.
Molybdenum (2.5–3.5%) raises pitting and crevice resistance; the alloy's PREN sits at roughly 30–32.
Copper (1.5–3.0%) is the distinguishing addition. It is what gives 825 its genuine resistance to reducing acids — sulphuric and phosphoric — where chromium alone offers little protection.
Titanium (0.6–1.2%) stabilises the alloy against chromium carbide precipitation, so welded and heat-affected zones resist intergranular attack without a post-weld solution anneal.

Where 825 Sits in the Corrosion Hierarchy

825 is a mid-tier corrosion alloy, and specifying it correctly means knowing both its floor and its ceiling. It comfortably outperforms 316L, 904L and Alloy 20 in mixed acid and chloride service. It does not match Hastelloy C-276 in hot hydrochloric acid, nor Inconel 625 in high-temperature or severe seawater crevice conditions. Buying 825 where C-276 is required is a false economy; buying C-276 where 825 would serve is money left on the table.

Field observation from our works: the most common misuse of Alloy 825 bolting we see is temperature, not chemistry. Buyers treat "Incoloy" as a synonym for "high temperature" and specify 825 for furnace or exhaust hardware. It is not that alloy. Sustained service above roughly 540°C (1000°F) risks sensitisation and loss of corrosion performance. For hot service, Incoloy 800/800HT or Inconel 600 is the correct choice — and we will tell you so before quoting.

Related products in the same alloy: Incoloy 825 round bars for machined specials and Incoloy 825 tube plugs for heat-exchanger repair. Browse the complete nickel alloy fasteners catalogue for adjacent grades.

Complete Incoloy 825 Fastener Product Range

Unifit Fastener manufactures more than 40 fastener forms in Alloy 825, produced in-house or from our own certified bar stock — we do not re-badge trading material.

Incoloy 825 Bolts

Incoloy 825 Nuts

Incoloy 825 Washers

Incoloy 825 Screws

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Technical Data

Incoloy 825 Fasteners — Standard Specification Sheet

Parameter	Specification
Material Grade	Incoloy 825 / Alloy 825 / Nickel Alloy 825
UNS Designation	UNS N08825
Werkstoff Number	2.4858
Alloy Type	Titanium-stabilised nickel-iron-chromium alloy with molybdenum and copper
Governing Standards	ASTM B425, ASME SB425 (rod and bar); ASTM B564, ASME SB564 (forgings); ASTM B424 (plate and sheet); ASTM F467, ASTM F468 (finished nuts and bolts)
Dimensional Standards	ASME B18.2.1, ASME B18.2.2, ASME B18.3, ASME B18.21.1, DIN 931, DIN 933, DIN 934, DIN 125, DIN 976, DIN 7991, ISO, JIS, BS, GB, IS
Supply Condition	Solution annealed (standard for Alloy 825 fasteners)
Size Range (Bolts)	M3 – M100 \| 3/16" to 4" \| custom sizes on request
Size Range (Nuts)	M3 – M56 \| 3/16" to 2"
Size Range (Washers)	M3 – M56 \| 3/16" to 2"
Length Range	3 mm to 200 mm and above (custom lengths available)
Thread Types	UNC, UNF, UN, 8UN, BSW, BSF, metric coarse, metric fine, left or right hand
Thread Configuration	ASME B1.1 2A/3A – 2B/3B inch unified; ASME B1.13M 6g–6H metric coarse
Head Styles	Hex, heavy hex, square, round, flange, countersunk, socket, button, truss, T-head
Manufacturing Route	Cold heading, hot forging, CNC turning, thread rolling, solution annealing
Surface Finish	Pickled and passivated (standard), bright, polished, mill, Xylan, PTFE, zinc-nickel, electroless nickel
Tolerance	OEM / ODM to drawing; ±0.03 mm achievable on machined features
Test Certificate	EN 10204 / 3.1 mill test certificate; PED 97/23/EC and AD 2000 W2 on request
Additional Compliance	NACE MR0175 / ISO 15156 for sour service; free from mercury and radioactive contamination on request
Certification	Dual certified to ASTM and ASME codes
Delivery	Standard products 7–15 days; custom products 2–4 weeks
Country of Origin	India (Mumbai, Maharashtra)

Chemical Composition of Incoloy 825 Fasteners (UNS N08825)

Element	Symbol	Weight %	Metallurgical Role
Nickel	Ni	38.00 – 46.00	Chloride SCC resistance; austenitic stability
Iron	Fe	22.00 min	Balance element; keeps cost below fully nickel-based alloys
Chromium	Cr	19.50 – 23.50	Passive film for oxidising acids and general corrosion
Molybdenum	Mo	2.50 – 3.50	Pitting and crevice resistance in chlorides
Copper	Cu	1.50 – 3.00	The key addition — resistance to reducing acids (H₂SO₄, H₃PO₄)
Titanium	Ti	0.60 – 1.20	Stabiliser against chromium carbide precipitation and intergranular attack
Manganese	Mn	1.00 max	Deoxidiser; sulphur control
Silicon	Si	0.50 max	Deoxidiser
Carbon	C	0.05 max	Restricted to limit sensitisation risk
Aluminium	Al	0.20 max	Residual limit
Sulphur	S	0.03 max	Restricted to protect hot workability

Mechanical Properties of Incoloy 825 Fasteners (Solution Annealed)

ASTM B425 Minimum	Typical Value
586 MPa / 85,000 psi	~690 MPa / 100,000 psi
241 MPa / 35,000 psi	~310 MPa / 45,000 psi
30% min	35 – 45%
~75 – 90 HRB	~80 HRB

Physical Properties of Incoloy 825

Property	Value
Density	8.14 g/cm³ (0.294 lb/in³)
Melting Range	1370 – 1400 °C (2500 – 2550 °F)
Modulus of Elasticity (RT)	~196 GPa (28 × 10⁶ psi)
Specific Heat	440 J/kg·K
Thermal Conductivity (RT)	11.1 W/m·K
Electrical Resistivity (RT)	~1.13 µΩ·m (113 µΩ·cm)
Mean Coefficient of Thermal Expansion (20–100°C)	~14.0 µm/m·°C
Recommended Maximum Service Temperature	~540 °C (1000 °F) for sustained service
PREN (Cr + 3.3Mo)	~30 – 32
Magnetic Response	Non-magnetic (austenitic)

Equivalent Grades & International Designations

Standard	Werkstoff Nr.	UNS	JIS	BS	GOST	AFNOR	EN
Incoloy 825	2.4858	N08825	NCF 825	NA 16	ЭИ703	NFE30C20DUM	NiCr21Mo

Incoloy 825 Bolts & Screws

Bolt / Screw Type	Common Standard	Typical Use Case
Hex bolts / hex head bolts	ASME B18.2.1, DIN 931/933	General flange and structural bolting in acid service
Heavy hex bolts	ASME B18.2.1	Pressure-boundary flanged joints
Socket head cap screws	ASME B18.3, DIN 912	Pumps, valve internals, compact process equipment
Button and truss head screws	ISO 7380	Low-profile covers and guards
Countersunk / flat head screws	DIN 7991, ISO 10642	Flush-mounted liners and tank internals
Flange head bolts	DIN 6921	Vibration-prone joints without a separate washer
Carriage bolts and square head bolts	DIN 603 / ASME B18.2.1	Through-bolted plate, lining and cladding work
U bolts, J bolts, eye bolts, hook bolts	DIN 580 / custom	Pipe support, lifting and tube clamping
Anchor bolts, sleeve and wedge anchors	ASTM B564 / drawing	Equipment and foundation anchoring in corrosive plants
Set screws and grub screws	DIN 913–916	Shaft and collar location
Self-drilling, self-tapping and hi-lo screws	DIN 7504 / 7981	Sheet, duct and FRP-adjacent fixings
Machine screws, lag screws, wood screws	ISO 14579 / custom	General assembly and support hardware

Incoloy 825 Nuts

Nut Type	Common Standard	Typical Use Case
Hex nuts	ASTM F467, DIN 934	Standard mating nut for Alloy 825 bolting
Heavy hex nuts	ASTM F467, ASME B18.2.2	Pressure-boundary flange joints
Hex jam / thin nuts	DIN 439	Locking and clearance-limited joints
Nyloc / nylon insert lock nuts	DIN 985	Vibration resistance below the polymer temperature limit
All-metal prevailing torque lock nuts	DIN 980	Vibration locking where polymer inserts are unsuitable
Castle and slotted nuts	DIN 935	Cotter-pin retention
Dome / acorn / cap nuts	DIN 1587	Thread protection against acid ingress and splash
Coupling nuts	DIN 6334	Threaded rod extension
Wing nuts, eye nuts, handle nuts, T-nuts	DIN 315 / custom	Hand-adjusted access hardware
Square nuts, cage nuts, panel nuts	DIN 557 / custom	Channel fixing and enclosure work
Weld nuts, rivet nuts, self-clinching nuts	DIN 928 / custom	Blind and sheet-metal fastening

Incoloy 825 Stud Bolts & Threaded Rods

Stud / Rod Type	Description
Fully threaded stud bolts	Continuous thread both ends — the standard ASME B16.5 flange stud
Double-ended studs (tap-end / nut-end)	Plain centre body with threaded ends for tapped-hole assemblies
Half-threaded and partial-thread studs	Where a plain grip length passes through the joint
Reduced-shank stud bolts	Waisted body for controlled elongation and improved fatigue performance
Threaded rods / all-thread rod	DIN 976, cut to length or supplied in standard bar lengths
Weld studs and clinch studs	Attachment hardware for vessel and duct fabrication
Tie rods, rod ends and turnbuckles	Adjustable restraint hardware in corrosive plant
Dowel pins and precision studs	Location hardware machined to h6 tolerance

Incoloy 825 Washers

Washer Type	Standard	Function
Plain / flat washers	DIN 125, DIN 126, ASME B18.21.1	Load distribution under head or nut
Fender and structural washers	F436 style / custom	Large bearing area on oversized or soft-lined holes
Spring / split lock washers	DIN 127	Vibration resistance in cycled joints
Belleville / conical spring washers	DIN 6796	Preload maintenance through thermal and chemical cycling
Tab washers and lock plates	DIN 93 / 463	Positive mechanical locking
Star / serrated tooth lock washers	DIN 6797 / 6798	Anti-rotation on coated or lined surfaces
Square, ogee and dock washers	Custom	Heavy plate and structural work
Sealing and bonded washers	Custom	Fluid-tight fixings on panels and tank roofs

Fold 7 — Corrosive Environments: Where Alloy 825 Actually Performs

Environment	Alloy 825 Performance	Practical Guidance
Sulphuric acid (H₂SO₄)	Very good across a wide concentration and temperature band	The classic application — pickling lines, acid plants, battery-grade handling
Phosphoric acid (H₃PO₄)	Very good, including wet-process conditions	Fertiliser plants and phosphoric acid evaporators
Chloride-bearing streams	Effectively immune to chloride stress corrosion cracking	Where 304 and 316 studs crack, 825 does not
Seawater	Good in flowing conditions	For stagnant or crevice-prone seawater, consider Inconel 625 or super duplex
Sour gas / H₂S service	Suitable when procured to NACE MR0175 / ISO 15156	State the requirement at enquiry stage — it is not automatic
Sulphur-bearing flue gases	Good — a standard FGD and pollution-control material	Absorber internals, ducting and damper hardware
Nitric and other oxidising acids	Good	Chromium content carries the oxidising duty
Organic acids and alkalis	Good	Broad process-industry suitability
Hot hydrochloric acid	Limited — not the right alloy	Specify Hastelloy C-276 or C-22 instead
Sustained high temperature (>540°C)	Not suitable — sensitisation risk	Specify Incoloy 800/800HT or Inconel 600

Fold 8 — Temperature Limits and Heat Treatment

Parameter	Value	Why It Matters
Recommended maximum sustained service temperature	~540 °C (1000 °F)	Above this, prolonged exposure risks carbide precipitation and loss of corrosion resistance
Sensitisation risk band	~650 – 760 °C (1200 – 1400 °F)	Avoid prolonged holds here; the titanium stabiliser helps but does not make the alloy immune
Solution annealing temperature	~930 – 980 °C (1710 – 1800 °F), rapid cool	Restores a homogeneous austenitic structure and dissolves carbides
Stabilise anneal (where specified)	~940 °C, controlled cool	Used where maximum intergranular attack resistance is required
Hot working range	~870 – 1180 °C	Forging window for heads and anchors
Low-temperature capability	Cryogenic — no ductile-to-brittle transition	Usable in refrigerated and cryogenic process hardware

Fold 9 — Incoloy 825 Bolt Torque Guidance

Read this before using any 825 torque chart you find online. Published nickel-alloy torque tables are frequently built around higher-strength grades and then reused for Alloy 825 without adjusting the proof stress. A 1/2"–13 figure in the 69–78 ft-lb range — which is common in circulated tables — implies a bolt stress of about 58 ksi. The ASTM B425 minimum yield for Alloy 825 is 35 ksi. On minimum-property material, that would take the fastener past yield during assembly.

The Method

Size (UNC)	Tensile Stress Area (in²)	Target Preload (lbf)	Torque, Dry K=0.20 (ft-lb)	Torque, Lubricated K=0.15 (ft-lb)
3/8"–16	0.0775	1,763	11	8
1/2"–13	0.1419	3,228	27	20
5/8"–11	0.2260	5,142	54	40
3/4"–10	0.3340	7,599	95	71
7/8"–9	0.4620	10,511	153	115
1"–8	0.6060	13,787	230	172
1-1/4"–8	1.0000	22,750	474	355

Fold 10 — Applications & Industries Served

Industry	Where Incoloy 825 Fasteners Are Used	Why This Alloy Wins
Sulphuric acid production & pickling	Acid plant bolting, pickling line hardware, tank and launder fixings	The alloy was developed for exactly this duty
Phosphoric acid & fertiliser	Evaporators, reactor internals, agitator and pump hardware	Copper addition resists wet-process phosphoric attack
Oil & gas — sour service	Wellhead bolting, downhole hardware, separator internals	H₂S resistance under NACE MR0175 procurement
Chemical processing	Heat exchangers, reactors, piping supports, agitator shafts	Handles mixed oxidising and reducing streams
Pollution control & FGD	Absorber internals, ducting, damper and expansion joint hardware	Resists sulphur-bearing flue gas condensate
Nuclear fuel reprocessing	Spent fuel handling, storage and auxiliary reprocessing hardware	Nitric acid resistance with controlled contamination limits
Marine & offshore	Seawater heat exchangers, splash-zone fixings, platform hardware	Chloride SCC immunity with useful pitting resistance
Pulp & paper	Digesters, bleach plant hardware, recovery equipment	Chloride and acid resistance in wet service
Power generation	Condenser and cooling water hardware, FGD systems	Long service life in chloride-bearing cooling circuits
Pharmaceutical & food processing	Reactor and clean-in-place skid hardware	Non-contaminating, cleanable passive surface

Corrosion Alloy Selection Grid

Grade	Nominal Ni	PREN (approx.)	Min Yield	Best Suited To
Incoloy 825	38 – 46%	~30 – 32	35 ksi (241 MPa)	Sulphuric and phosphoric acid, chlorides, sour service
Alloy 20 (N08020)	32 – 38%	~30	35 ksi (241 MPa)	Sulphuric acid focus; slightly lower chloride capability
Stainless Steel 904L	23 – 28%	~34	31 ksi (216 MPa)	Dilute sulphuric acid on a tighter budget
Incoloy 800 / 800HT	30 – 35%	N/A (heat-focused)	30 ksi (205 MPa)	High-temperature process hardware, not acid service
Inconel 625	58% min	~45	60 ksi (414 MPa)	Severe seawater, high temperature, high strength
Hastelloy C-276	57% min	~68	41 ksi (283 MPa)	Hot hydrochloric acid and the most aggressive media

Incoloy 825 vs Stainless Steel 316L vs Inconel 625

Criterion	Incoloy 825	Stainless Steel 316L	Inconel 625
Nominal nickel content	38 – 46%	10 – 14%	58% min
Sulphuric acid resistance	Very good (copper-bearing)	Poor	Good
Chloride SCC resistance	Effectively immune	Poor above ~60°C	Effectively immune
Pitting resistance (PREN)	~30 – 32	~24	~45
Max sustained temperature	~540°C	~870°C (scaling limit)	~982°C
Minimum yield strength	35 ksi	30 ksi	60 ksi
Relative cost index	Medium-high	Low	High
Best-fit duty	Acid service with chlorides	General corrosion service	Severe seawater and high temperature

Testing We Perform

Test	Purpose	Availability
Positive Material Identification (PMI)	Confirms alloy grade before dispatch	100% of lots
Chemical analysis (spectro)	Verifies composition against ASTM B425	Per heat
Tensile, yield and elongation	Confirms mechanical class against B425 minima	Per lot / per heat
Hardness (Rockwell / Brinell)	Confirms annealed condition	Per lot
Intergranular corrosion test (ASTM G28)	Confirms freedom from sensitisation — critical for 825	On request / per spec
Pitting corrosion test (ASTM G48)	Validates chloride performance	On request
Ultrasonic and radiographic testing	Internal flaw detection in billets and large studs	On request / per spec
Dye penetrant (DP) testing	Surface crack detection	On request
Impact and flattening tests	Ductility verification where specified	On request
Third-party inspection	TÜV, BV, SGS, Lloyd's witness inspection	On request

Fold 14 — Standards, Certifications & Documentation

Standard	Scope for Incoloy 825 Fasteners
ASTM B425 / ASME SB425	Nickel-iron-chromium-molybdenum-copper alloy rod and bar — the primary stock standard for 825 fasteners
ASTM B564 / ASME SB564	Nickel alloy forgings — heavy hex heads, anchors and forged specials
ASTM B424 / ASME SB424	Plate, sheet and strip — relevant for washers and formed hardware
ASTM F467 / ASME SF467	Nonferrous nuts for general use
ASTM F468 / ASME SF468	Nonferrous bolts, hex cap screws and studs for general use
NACE MR0175 / ISO 15156	Sour service qualification — specify explicitly at enquiry stage
ASME B18.2.1 / B18.2.2 / B18.3	Dimensional standards for inch bolts, nuts and socket screws
ASME B1.1 / B1.13M	Unified inch and metric thread tolerance classes
DIN 931 / 933 / 934 / 125 / 976	Metric bolt, nut, washer and threaded rod dimensions
EN 10204 3.1	Mill test certificate issued by the manufacturer's independent inspection function
PED 97/23/EC, AD 2000 W2	Pressure equipment conformity documentation (on request)

Fold 15 — Why Buy Incoloy 825 Fasteners From Unifit Fastener

EEAT Pillar	What Unifit Fastener Delivers
Experience	Production and export experience across acid plant, fertiliser, refinery, FGD and marine bolting projects — including emergency turnaround supply where the shutdown date, not the price, is the constraint.
Expertise	In-house metallurgists who advise on alloy selection against your actual service chemistry, plus thread class, anti-galling strategy and preload method before you buy.
Authoritativeness	Manufacturing to ASTM, ASME, DIN, ISO, JIS, BS and IS; dual certification; acceptance by third-party inspection agencies and EPC approval processes.
Trustworthiness	Heat-number traceability, EN 10204 3.1 certification as standard, correct standard references on every certificate, and published technical data that matches what we ship.

Fold 16 — Incoloy 825 Fasteners Price: What Actually Drives Your Quote

Cost Driver	Effect on Price
LME nickel, chromium and molybdenum pricing	The dominant input; raw material is typically 60–70% of a finished fastener cost
Size and section	Large-diameter studs and heavy hex nuts consume disproportionately more bar stock
Standard vs custom geometry	Catalogue DIN/ASME items cost far less than drawing-specific specials requiring new tooling
Thread type and class	3A/3B and fine threads require tighter control and add cost over 2A/2B
Order quantity	Cold-headed volume runs are materially cheaper per piece than machined small batches
Surface treatment	Xylan, PTFE, electroless nickel and zinc-nickel add per-piece processing
Testing and compliance route	G28 / G48 corrosion testing, NACE MR0175 procurement and witnessed inspection add cost and lead time
Delivery urgency	Expedited turnaround supply carries a premium over planned procurement

Our Manufacturing & Quality Process

Step-by-Step Production Route

Raw material intake — certified Alloy 825 bar and wire from approved mills, verified against the mill certificate on arrival.
Incoming PMI and chemistry check — optical emission spectroscopy confirms Ni, Cr, Mo, Cu and Ti before material enters production.
Forming — cold heading for volume sizes; hot forging between roughly 870°C and 1180°C for heavy heads and anchors.
Machining and thread production — CNC turning for specials; threads rolled wherever section permits, for better grain flow and fatigue life than cut threads.
Solution annealing — restores a homogeneous austenitic structure and dissolves chromium carbides.
Pickling and passivation — the standard finish for 825, ensuring a fully developed passive film before service.
Optional surface treatment — Xylan, PTFE, electroless nickel or zinc-nickel where anti-galling or torque control is specified.
Inspection and testing — dimensional, hardness, tensile and corrosion testing against the applicable ASTM clause.
Marking, documentation and packing — heat number stamped, EN 10204 3.1 certificate issued, VCI wrapping and export-grade boxing.

FAQ's About Incoloy 825 Fasteners

What is the tensile strength of Incoloy 825 bolts?

The ASTM B425 specification minimum for solution-annealed Alloy 825 is 586 MPa (85,000 psi) tensile and 241 MPa (35,000 psi) yield, with 30% minimum elongation. Typical certified mill results run higher — often around 690 MPa tensile and 310 MPa yield — but joint calculations should always use the specification minimum unless you are designing against a specific certificate.

What is the maximum temperature for Incoloy 825 fasteners?

Approximately 540°C (1000°F) for sustained service. Alloy 825 is a corrosion-resistant alloy, not a high-temperature one, and prolonged exposure above that range risks carbide precipitation and loss of corrosion performance. For hot service, specify Incoloy 800/800HT or Inconel 600 instead.

Is Incoloy 825 resistant to sulphuric acid?

Yes — it is the alloy's defining property. The 1.5–3% copper addition provides genuine resistance to reducing acids including sulphuric and phosphoric acid across a wide concentration and temperature range, which chromium-only alloys cannot match. This is why 825 dominates pickling lines, acid plants and phosphoric acid evaporators.

Why is titanium added to Incoloy 825?

Titanium acts as a stabiliser. It preferentially combines with carbon to form titanium carbides, preventing chromium from being drawn out of solution to form chromium carbides at grain boundaries. That protects the heat-affected zone of welds from intergranular attack without requiring a post-weld solution anneal.

What is the difference between Incoloy 825 and Inconel 625 fasteners?

825 is a nickel-iron-chromium alloy with copper, optimised for sulphuric and phosphoric acid service at moderate temperature. 625 is a fully nickel-based alloy with molybdenum and niobium, offering roughly double the yield strength, far higher pitting resistance (PREN ~45 versus ~31) and service to about 982°C. Choose 825 for acid duty and value; 625 for severe seawater, high temperature or higher strength.

Get Your Incoloy 825 Fastener Quote in One Working Day

Send us your drawing, service chemistry, standard and quantity — our engineering team will confirm that Alloy 825 is the right grade for your exposure before quoting. If a cheaper alloy will do the job, we will say so. No obligation, no generic price lists.

Speak to a Corrosion Engineer — call or WhatsApp us today.

Not sure which grade you need? Compare Alloy 20, 904L and Hastelloy C-276, or contact our team for a recommendation.

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