Inconel 718, a high-strength, corrosion-resistant nickel-based alloy, is widely used in extreme environments—ranging from aerospace engines to offshore platforms. But when designing or sourcing Inconel 718 components, engineers are often faced with a key decision: Should you use Inconel 718 seamless pipe or solid rod (bar) stock?

This article by SASA ALLOY breaks down the technical, functional, and cost-related considerations that determine when tubular forms are preferred over solid bars.

1. Structural Differences

Inconel 718 Pipe: Hollow cylinder, usually produced via extrusion or forging and heat-treated per ASTM B444/B829. Ideal for pressure-bearing, fluid-carrying, or weight-sensitive systems.
Inconel 718 Rod: Solid cylindrical form, typically forged or rolled to ASTM B637. Offers maximum strength and is often used for machining into fasteners, shafts, or custom fittings.

2.When to Choose Inconel 718 Seamless Pipe

Inconel 718 pipes are preferred in applications where internal flow (liquid or gas), pressure containment, or weight reduction is important. These include:

• High-pressure tubing in aerospace or nuclear systems
• Hydraulic or fuel lines in jet engines
• Heat exchanger tubing in chemical reactors
• Piping systems in corrosive oil & gas environments
The seamless structure ensures integrity under pressure, while the hollow design reduces unnecessary mass—critical in weight-sensitive sectors like aerospace.

3. When to Use Rod (Bar) Stock

Solid Inconel 718 bars are better suited for components requiring maximum mechanical strength, extensive machining, or structural rigidity. Use cases include:

High-strength bolts, fasteners, and threaded connectors
Rotor shafts and bearing housings
Valve stems and pump shafts
Custom-machined aerospace hardware

Rods offer better machinability for parts that require tight tolerances or complex geometries.

4. Cost Considerations

While Inconel 718 pipes are generally more expensive per unit weight due to complex forging and piercing processes, they may result in cost savings when weight reduction eliminates over-engineering or improves energy efficiency.

5. Summary Table: Pipe vs Rod

Criteria	Inconel 718 Seamless Pipe	Inconel 718 Rod (Bar)
Form	Hollow	Solid
Best For	Fluid flow, pressure systems	Machined parts, structural loads
Weight Efficiency	High	Low
Machining Volume	Low	High
Cost	Higher per kg	Lower per kg

Conclusion

Choosing between Inconel 718 pipe and rod depends on your application’s mechanical, thermal, and dimensional requirements. If the component involves internal pressure or needs to reduce weight, Inconel 718 seamless pipe is the optimal solution. For highly loaded, machined components, bar stock remains the preferred form.

SASA ALLOY supplies both forms with full MTC