Nickel Alloy Alloy 684 vs Alloy 689
Nickel Alloy · grade comparison
Nickel Alloy Alloy 684 and Alloy 689 are both nickel alloy grades. Alloy 684 is the stronger of the two: tensile strength 1,310 MPa (190 ksi) against 1,240 MPa (180 ksi) for Alloy 689, about 6% more. Alloy 684 is harder — 355 HB against 331 HB for Alloy 689 — which matters for wear surfaces and threads. Alloy 684 is lighter (8.02 g/cm³ vs 8.27 g/cm³ for Alloy 689). On the shop floor, Alloy 689 welds better (30 vs 20 out of 100) and Alloy 689 forms better (fair vs poor).
Alloy 684Choose it when strength drives the design, or when surface hardness matters.
Alloy 689Choose it when it will be welded.
Alloy 684 vs Alloy 689: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all nickel alloy grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all nickel alloy grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Shear Modulus
Bulk Modulus
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Compressive Strength
Shear Strength
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell C
Hardness, Vickers
Same in both: Poisson's Ratio 0.3 · Elongation at Break 16% · Reduction in Area 20% · Fatigue Strength (Endurance Limit) 480 MPa69.6 ksi
Physical
Density and transition temperatures.
Density
Melting Point (Solidus)
Liquidus Temperature
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Same in both: Specific Heat Capacity 420 J/kg·K0.1 BTU/lb·°F · Latent Heat of Fusion 290 J/g125 BTU/lb · Min Service Temperature -196°C-321 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Galvanic Potential (seawater, vs SCE)
Corrosion Resistance
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Castability
Same in both: Brazeability / Solderability 40 / 100 · Polishability 70 / 100
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Typical Recycled Content
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Modulus of Resilience
Thermal Diffusivity
Same in both: Thermal Shock Resistance Index 6
Strength versus weight
Yield strength against density for every nickel alloy grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | Alloy 684 | Alloy 689 |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$$$ High | $$$$ High |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Both take the same 3 finishes: Gold Plating, Plasma Spray, Silver Plating.
Alloy 684 vs Alloy 689 — frequently asked
Is Alloy 684 stronger than Alloy 689?
Yes. Alloy 684 has a typical tensile strength of 1,310 MPa (190 ksi) against 1,240 MPa (180 ksi) for Alloy 689 — about 6% more.
Which is cheaper, Alloy 684 or Alloy 689?
Both sit in the same relative cost tier ($$$$, high); the part price will be decided by machining time, tolerance and quantity rather than by the material.
Which welds better, Alloy 684 or Alloy 689?
Alloy 689. Its weldability rates poor (30/100) against poor (20/100) for Alloy 684.
Ready to make it?
Upload a CAD file and FabDigit prices the part in Alloy 684 and Alloy 689 side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.