Bar and Rod
Plate and Sheet
Strip
Pipe and Tube
Wire
Welding
Powder Material
Cast Products
Forged Products
Fittings
Fastening
Round Bar:
φ2–500 mm, 1–6 m length
Flat/Square Bar:
4–100 mm thickness/width
Hex Bar:
A/F 3–100 mm
Hollow Bar:
OD 20–300 mm
Sheet:
0.3–6 mm thickness
Medium Plate:
6–25 mm thickness
Heavy Plate:
25–100 mm thickness
Standard Strip:
0.05–3 mm thick,
10–600 mm wide
Precision strip:
0.01–0.5 mm thick,
tight tolerance ±0.005 mm
Foil:
0.005–0.1 mm thick
Seamless Tube:
OD 6–450 mm,
WT 1–50 mm,
1–12 m length
Welded Tube:
OD 10–600 mm,
WT 1–20 mm
Capillary Tube:
OD 1–10 mm,
WT 0.1–2 mm
Wire Form:
Cold Drawn Wire,
Bright Wire,
Spring Wire,
Fine Wire,
Ultra-fine Wire
General Diameter:
φ0.1–10 mm
Coil Weight:
50–500 kg,
customizable tolerance
Solid Wire:
φ0.8–4.0 mm
Flux-cored Wire:
φ1.2–4.0 mm
Welding Rod:
φ2.0–5.0 mm
Powder Form:
AM 3D Printing Powder,
Spherical Powder,
Gas-atomized Powder,
Water-atomized Powder
Particle Size:
10–150 μm
Sphericity:
≥90% for AM grade
Cast Ingot:
φ200–800 mm
Precision Casting:
min wall 0.5 mm
Cast Pipe:
OD 100–600 mm,
WT 10–50 mm
Forged Bar:
Φ35–500 mm
Forged Ring:
OD 200–2000 mm
Forging Weight:
1–5000 kg
Fittings Form:
Elbow, Tee, Reducer, Flange, Cap, Outlet, Lap Joint
Size range:
1/2''–24'' (DN15–DN600)
Wall thickness:
Sch10–Sch160, STD, XS, XXS
Pressure Class:
150–2500 LB
Fastening Form:
Bolt, Nut, Screw, Stud, Washer, Pin, Rivet
Metric: M3–M64
Imperial: #4–2.5''
Length: 6–500 mm
Alloy 686 is a single-phase, austenitic nickel–chromium–molybdenum–tungsten alloy offering outstanding corrosion resistance across an exceptionally wide range of severe environments. This datasheet presents the material within the American (ASTM / ASME / UNS) standard system.
Its high nickel and molybdenum contents provide resistance under reducing conditions, while the high chromium content gives resistance to oxidising media. Molybdenum and tungsten together confer outstanding resistance to localised corrosion such as pitting and crevice attack, and iron is closely controlled to enhance properties. The very low carbon content minimises grain-boundary carbide precipitation, preserving corrosion resistance in the heat-affected zones of welded joints.
Resistance to general, pitting and crevice corrosion increases with combined (Cr + Mo + W) alloy content, and on this measure Alloy 686 ranks above most competitive materials, out-performing the Hastelloy C grades in mixed acids. It offers exceptional resistance to sulphuric and hydrochloric acids and to their mixtures, excellent resistance to stress-corrosion cracking, and excellent behaviour in seawater (general, galvanic and localised corrosion, and hydrogen embrittlement). It is used for the most aggressive media in chemical processing, pollution control, pulp and paper, oil and gas, and waste-management applications, with operating capability up to approximately 1000 °C.
Typical values, annealed condition.
| Property | Value | Unit |
|---|---|---|
| Density | 8.73 | g/cm³ |
| Melting range | 1338–1380 | °C |
| Elastic modulus | 207 | GPa |
| Coefficient of thermal expansion (20–100 °C) | 11.97 | µm/m·°C |
| Maximum operating temperature | ~1000 | °C |
| Structure | Single-phase austenitic (FCC) | — |
Specified per ASTM B574 / B575 (UNS N06686).
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Nickel | Ni | Balance | — | Austenitic FCC matrix; reducing-media resistance |
| Chromium | Cr | 19.0 | 23.0 | Resistance to oxidising media; passive film |
| Molybdenum | Mo | 15.0 | 17.0 | Pitting/crevice resistance; reducing-acid resistance |
| Tungsten | W | 3.0 | 4.4 | Enhances localised-corrosion resistance |
| Titanium | Ti | 0.02 | 0.25 | Stabiliser |
| Iron | Fe | — | 1.0 | Closely controlled to enhance properties |
| Carbon | C | — | 0.01 | Ultra-low; minimises HAZ carbide precipitation |
| Manganese | Mn | — | 0.75 | Deoxidiser |
| Silicon | Si | — | 0.08 | Deoxidiser |
| Phosphorus | P | — | 0.04 | Residual impurity |
| Sulphur | S | — | 0.02 | Residual impurity |
Typical values; confirm against the mill test certificate for each delivery.
| Condition | Tensile strength | Operating temperature |
|---|---|---|
| Annealed | <1000 MPa (<145 ksi) | Up to ~1000 °C |
| Spring temper | 1200–1600 MPa (174–232 ksi) | Up to ~1000 °C |
| Elastic modulus | 207 GPa | — |
The alloy is a single-phase solid-solution material; it is not age-hardenable. Higher strength is obtained by cold work.
| Environment | Performance | Notes |
|---|---|---|
| Sulphuric acid (H₂SO₄) | Outstanding | Out-performs Hastelloy C grades in mixed acids |
| Hydrochloric acid (HCl) | Outstanding | Exceptional resistance in hot acid solutions |
| Mixed acids (H₂SO₄ + HCl) | Outstanding | Superior to competitive Ni-Cr-Mo alloys |
| Pitting and crevice corrosion | Outstanding | High combined Cr + Mo + W content |
| Stress-corrosion cracking | Outstanding | High nickel content |
| Seawater / marine | Excellent | General, galvanic, localised corrosion; hydrogen-embrittlement resistance |
| Weld heat-affected zone | Excellent | Ultra-low carbon prevents sensitisation |
| Oxidising media | Very Good | High chromium content |
The alloy is a single-phase, solid-solution material and is NOT age-hardenable. Heat treatment is for solution annealing only.
Solution Anneal Purpose: Dissolves secondary phases, restores maximum corrosion resistance and ductility, recrystallises cold-worked structure. Followed by rapid cooling (water quench) to retain the single-phase structure and avoid intermetallic/grain-boundary precipitation.
Cold work is used to increase strength where required (e.g. spring temper); a subsequent solution anneal removes the effects of cold work.
Excellent weldability; the ultra-low carbon content preserves corrosion resistance in the heat-affected zone. Matched-composition welding products give as-welded resistance to sulphuric/hydrochloric acids and to crevice and pitting corrosion in hot acid-chloride solutions.
| Welding Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG | Excellent | AWS A5.14 ERNiCrMo-14 (INCO-WELD 686CPT) |
| GMAW / MIG | Excellent | AWS A5.14 ERNiCrMo-14 (INCO-WELD 686CPT) |
| SMAW / stick | Excellent | AWS A5.11 ENiCrMo-14 (686CPT electrode) |
The welding products are also used for dissimilar-metal and overmatched welding (e.g. joining super-duplex and super-austenitic stainless steels). No post-weld heat treatment is normally required.
Machining Guidelines
| Parameter | Recommendation |
|---|---|
| Work hardening | High rate (typical of Ni-Cr-Mo-W alloys); rigid setup, sharp tooling, positive rake |
| Cutting | Low speed, sufficient feed/depth to cut below the work-hardened layer |
| Coolant | Ample flood coolant |
| Preferred condition | Solution-annealed |
Forming Processes
| Process | Notes |
|---|---|
| Cold forming | Readily cold-formed; high work-hardening rate; intermediate solution anneal for heavy reductions |
| Hot forming | Followed by rapid cooling to retain single-phase structure |
| Wire / spring | Available from 0.025 mm to 21 mm; spring temper 1200–1600 MPa |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Chemical processing | Reaction vessels, heat exchangers, piping for mixed acids | Mixed-acid + pitting/crevice resistance |
| Pollution control | Flue-gas desulphurisation (FGD), scrubbers, ducting | Hot acid-chloride resistance |
| Pulp and paper | Bleaching equipment, digesters | Resistance to oxidising chlorine compounds |
| Oil and gas | Downhole tubulars, fasteners, sour-service components | SCC resistance; NACE MR0175 / ISO 15156 |
| Marine engineering | Seawater-handling components, fasteners | Seawater localised-corrosion + hydrogen-embrittlement resistance |
| Waste management | Incineration and waste-treatment hardware | Aggressive mixed-media resistance |
| Product Form | ASTM Standard | ASME Code |
|---|---|---|
| Rod and bar | ASTM B574 | ASME SB-574 |
| Plate, sheet and strip | ASTM B575 | ASME SB-575 |
| Seamless pipe and tube | ASTM B622 | ASME SB-622 |
| Welded pipe | ASTM B619 | ASME SB-619 |
| Welded tube | ASTM B626 | ASME SB-626 |
| Forgings | ASTM B564 | ASME SB-564 |
| Fittings | ASTM B366 | ASME SB-366 |
| Welding consumables | AWS A5.14 ERNiCrMo-14 | — |
Qualified for sour-service per ISO 15156-3 / NACE MR0175.
| Alloy | Ni % | Cr % | Mo % | Other | Best Used For |
|---|---|---|---|---|---|
| Alloy 686 | bal | 19–23 | 15–17 | W 3–4.4 | Mixed acids; FGD; severe pitting/crevice |
| Alloy C-276 | bal | 14.5–16.5 | 15–17 | W 3–4.5 | Reducing acids; classic Ni-Cr-Mo-W workhorse |
| Alloy C-22 | bal | 20–22.5 | 12.5–14.5 | W 2.5–3.5 | Oxidising+reducing; pitting/crevice |
| Alloy 625 | ≥58 | 20–23 | 8–10 | Nb 3.15–4.15 | Sea-water; chemical process; general |
| Alloy 825 | 38–46 | 19.5–23.5 | 2.5–3.5 | Cu 1.5–3 | Sulphuric acid; economy Fe-Ni-Cr-Mo |
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