This alloy is one of the most widely used nickel superalloys, found in jet engines, turbines, and oil and gas equipment. It keeps its strength at temperatures that would soften most metals, and that same toughness makes it difficult to machine. Understanding why helps you read a quote and plan a design.

What Makes It Special

It is a nickel-chromium alloy strengthened by precipitation hardening. One supplier lists typical room temperature properties after solution treatment and aging, including an ultimate tensile strength of about 1375 MPa, a yield strength of about 1100 MPa, and a hardness of 36 to 44 HRC. It holds its properties from cryogenic conditions up to about 700 degrees Celsius.

Why It Is Hard to Cut

The alloy work hardens, which means the surface becomes harder as it is cut. If the tool rubs instead of cutting, the material under it gets tougher and tool wear accelerates. Cutting forces are high, and the heat generated stays near the cutting edge instead of moving away with the chip.

How Shops Manage It

Shops use rigid machines and fixtures, controlled cutting speeds, and plenty of coolant. Tooling is typically coated carbide or ceramic. Toolpaths are planned to keep the cutter engaged and avoid dwelling, and tools are replaced before they wear far enough to damage the surface.

What It Does to Cost

• Raw material costs more than common alloys such as 6061 aluminum
• Cutting speeds are lower, so machine time is longer
• Tools wear faster and are replaced more often
• Heat treatment adds a step before or after machining
• Inspection is more important because the part is valuable

Designers choosing Inconel 718 should talk to the machinist early, because small design changes, such as larger corner radii, can cut machining time and tool wear noticeably.

Heat Treatment

The alloy is usually solution treated and then aged to develop its strength. Whether to machine before or after aging depends on the part, so ask the shop about the sequence.

Where It Is Used

Typical uses include turbine disks, engine components, downhole tools, fasteners, and high-pressure parts. In these jobs, the higher material and machining cost is often offset by long service life.

Do Not Overspecify

Use it where the temperature and stress justify it. Where they do not, a cheaper alloy will do the job and spare the budget.

Ask for a Trial Part

For a costly or critical part, consider machining one trial piece first. It reveals how the material behaves on the actual machine, and it lets the shop adjust speeds, tools, and fixtures before the full run begins.