- Grade / Alloy
- Alloy 686
- EN / W.Nr.
- 2.4606
- AISI / SAE
- —
- UNS
- N06686
- Family
- Solid-solution alloy
Chemical composition
Chemical composition
Composition limitsPublished composition limits for Alloy 686.
| Element | Content (% by mass) |
|---|---|
| CrChromium | 19–23 |
| MoMolybdenum | 15–17 |
| WTungsten | 3–4.4 |
| TiTitanium | 0.02–0.25 |
| FeIron | ≤ 2 |
| CCarbon | ≤ 0.01 |
| MnManganese | ≤ 0.75 |
| SSulfur | ≤ 0.02 |
| SiSilicon | ≤ 0.08 |
| PPhosphorus | ≤ 0.04 |
| NiNickel | Balance |
Values describe the grade, not the analysis of a specific batch. The applicable product specification and material certificate determine acceptance. A dash does not mean zero.
What kind of alloy is 686?
686 is distinguished primarily by corrosion resistance rather than the mechanical role of turbine alloys. Nickel, chromium, molybdenum and tungsten provide resistance to several chemical effects, making it relevant to equipment exposed to acids and chlorides.
What does localised corrosion mean?
Corrosion does not always affect a whole surface evenly. Chloride-containing solutions can cause pits or attack within narrow crevices. Molybdenum and tungsten contribute to resistance against these local effects, alongside the protective role of chromium.
Its place in chemical equipment
Condensed liquids in flue-gas systems may contain several chemicals. Reactors and acid lines can likewise present mixed environments. Alloy 686 is used in such duties, including tubing, exchangers and other wetted equipment surfaces.
Relationship to 625 and C-family alloys
686 is not another designation for 625 or C-276. Unlike niobium-bearing 625, it emphasises molybdenum and tungsten. Its applications overlap those of some C-family alloys, but its composition remains distinct.
Typical application areas
Chemical equipment, flue-gas treatment systems and acid lines.
Product and cutting options
Relevant product forms for this material are listed below. Availability varies with grade and dimensions.