Nickel Alloy Alloy 684 vs Inconel 617
Nickel Alloy · grade comparison
Nickel Alloy Alloy 684 and Inconel 617 are both nickel alloy grades. Alloy 684 is the stronger of the two: yield strength 860 MPa (125 ksi) against 330 MPa (47.9 ksi) for Inconel 617, about 161% more; tensile strength follows at 1,310 MPa (190 ksi) vs 760 MPa (110 ksi). In exchange, Inconel 617 is the more ductile: elongation 58% versus 16% for Alloy 684, and Alloy 684 is harder (355 HB vs 173 HB). Alloy 684 is lighter (8.02 g/cm³ vs 8.36 g/cm³ for Inconel 617) and Inconel 617 runs hotter in service (1,100°C vs 870°C continuous). On the shop floor, Inconel 617 welds better (very good vs poor).
Alloy 684Choose it when strength drives the design, or when weight is the constraint.
Inconel 617Choose it when the part is bent, formed or impact-loaded, or when the part sees heat.
Alloy 684 vs Inconel 617: 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)
Elongation at Break
Reduction in Area
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell C
Hardness, Vickers
Hardness, Rockwell B
Same in both: Poisson's Ratio 0.3
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
Specific Heat Capacity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Same in both: Latent Heat of Fusion 290 J/g125 BTU/lb · Min Service Temperature -196°C-321 °F
Electrical
Conductivity and insulation.
Electrical Resistivity
Same in both: Electrical Conductivity 1.4 % IACS
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
Brazeability / Solderability
Same in both: 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
Thermal Shock Resistance Index
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 | Inconel 617 |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$$$ High | $$$$ High |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Both take the same 3 finishes: Gold Plating, Plasma Spray, Silver Plating.
Alloy 684 vs Inconel 617 — frequently asked
Is Alloy 684 stronger than Inconel 617?
Yes. Alloy 684 has a typical yield strength of 860 MPa (125 ksi) against 330 MPa (47.9 ksi) for Inconel 617 — about 161% more. Tensile strength is 1,310 MPa (190 ksi) vs 760 MPa (110 ksi).
Which is cheaper, Alloy 684 or Inconel 617?
Both sit in the same relative cost tier ($$$$, high); the part price will be decided by machining time, tolerance and quantity rather than by the material.
Which is easier to machine, Alloy 684 or Inconel 617?
Inconel 617. Its machinability rates poor (18/100) against not recommended (12/100) for Alloy 684; for welding the order is Inconel 617 first (very good, 75/100) then Alloy 684 (poor, 20/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in Alloy 684 and Inconel 617 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.