Inconel 718 is a precipitation-hardenable nickel-chromium superalloy that maintains exceptional yield, tensile, and creep-rupture strength at extreme operating temperatures up to 700°C (1300°F).
Engineering Specifications & Parameters
Density
8.19 g/cm³
Hardness (Aged)
40 - 45 Rockwell C (HRC)
Machinability Rating
12% (Extreme Difficulty)
Thermal Conductivity
11.4 W/m·K (Very Low)
Tensile Strength (20°C)
1375 MPa (200,000 psi)
Tensile Strength (650°C)
1100 MPa (160,000 psi)
Superalloy Characteristics & High Heat Challenges
Inconel 718 contains ~52% nickel, 19% chromium, and 5% niobium/tantalum. Its high strength at elevated temperatures and low thermal conductivity cause 80%+ of cutting heat to transfer directly into the cutting tool edge.
Advanced Machining Strategies
Cutting Speed (Carbide): 25 – 45 m/min. Speeds above 50 m/min result in rapid notch wear and tool plastic deformation.
High-Pressure Coolant (HPC): 70 to 300 bar through-spindle coolant aimed directly at the tool-chip interface to break chips and suppress work-hardening.
Ceramic / Whisker-Reinforced Inserts: For high-speed roughing of Inconel 718, ceramic inserts operate at 200 – 300 m/min, intentionally generating high friction to soften material ahead of the cut.
Frequently Asked Questions
What causes severe notch wear when machining Inconel 718?
The combination of severe work-hardening at the depth-of-cut line and high mechanical shear strength rapidly erodes carbide tool edges at the DOC transition.
How does ceramic insert roughing work on Inconel 718?
Ceramics operate at 6x higher cutting speeds than carbide, creating localized thermal softening in the shear zone to evacuate high material volumes quickly.
