Few materials test the limits of machinists and their equipment like Inconel® 718. This nickel-based superalloy, a staple in aerospace applications, offers excellent strength and heat resistance—but those same properties make it notoriously difficult to machine.

Inconel 718 tends to work-harden quickly, generating extreme heat at the tool–workpiece interface, and accelerating tool wear. For decades, engineers have sought ways to manage these challenges through advanced tooling, optimized cutting parameters, and new machining strategies. But one factor is often overlooked: the machining fluid.

Independent studies have shown that choosing the right machining fluid can make a measurable difference in tool life, surface finish, and cycle time. Here’s why Inconel 718 is so difficult to machine—and how the right fluid helps overcome its toughest challenges.

Why Nickel 718 is Difficult to Machine

Nickel 718’s legendary strength, age-hardening behavior, and poor thermal conductivity make it one of the hardest materials to machine in aerospace:

• Rapid Work Hardening: Nickel 718 rapidly increases in hardness as it’s cut, requiring sharper tools and greater force.
• Low Thermal Conductivity: The alloy’s poor thermal conductivity means heat builds up at the cutting edge rather than dissipating, leading to increased temperature at the cutting edge and accelerated tool wear.
• High Machining Forces and Tool Wear: Its toughness generates high shear stress at the tool tip, requiring robust tooling and forcing machinists to slow down speeds.
• Surface Finish Sensitivity: Its tendency to gall and form built-up edges makes meeting tight tolerances more difficult (if not impossible).

These are some of the most persistent Inconel® 718 machining challenges, which is why fluid choice can make such a surprising difference.

The Role of Machining Fluids in Nickel 718 Machining

Machining fluids can address these challenges by providing the following:

• Lubrication: Reduces friction at the tool–chip interface, lowering cutting forces.
• Cooling: Helps dissipate heat away from the cutting zone.
• Chip Evacuation: Improves chip flow, reducing built-up edge and tool breakage.
• Surface Integrity: Consistent lubrication produces smoother surfaces and tighter dimensional control.

In a third-party study conducted by Kratos SRE, Halocarbon metalworking fluids (MWFs) were able to dramatically improve machining performance when compared to a leading competitive machining fluid that is typically used in the machining of Inconel® 718.

Below are images of tool-wear on 3/8” End-mill inserts taken post-machining. In the study, Kratos SRE needed to use two end-mills to complete the machining operations on nickel718 when using a competitive control fluid (CCF).  In contrast the same nickel 718 component was successfully machined using only one end-mill when using the Halocarbon MWF32. The results clearly show that in the studies using Halocarbon MWF, the end-mills retained their tool edges significantly longer, while the studies using the CCF rendered end-mills that were significantly chipped at the corners and suffered catastrophic edge fractures.

Halocarbon MWF:  3/8” Carbide end-mill after machining test articles using Halocarbon MWF 32.

Competitive Fluid: Two separate 3/8” Carbide end-mills after machining test articles using Competitive Control Fluid (CCF).

Similarly, the Halocarbon MWF used in this study also demonstrated significant tool life improvement across other types of machining operations: drilling and groove cutting.   In all cases, the effects of Halocarbon MWF on preserving machining tools is clearly evident.

Halocarbon MWF:  Machining insert using Halocarbon MWF 32 shows low wear after completing 24 holes.  This tool can continue to machine additional parts.

Competitive Fluid: Machining insert using Competitive Control Fluid (CCF) shows significant wear after completing 24 holes. This tool requires replacement before machining additional parts.

Halocarbon MWF:  Machining insert using Halocarbon MWF 32 shows low edge wear.  This tool can continue to machine additional parts.

Competitive Fluid: Machining insert using Competitive Control Fluid (CCF) shows significant edge wear. This tool has limited useful life.

The Halocarbon Advantage

In addition to providing tool-life extension, Halocarbon MWFs also provided significant improvements to machining efficiency, workpiece quality, and overall cycle time reduction. Halocarbon worked with Kratos SRE to perform a definitive head-to-head study of a Halocarbon MWF against a leading competitive control fluid.  In this study, nickel 718 was machined using 13 discrete machining operations.  The results below demonstrate that Halocarbon MWFs can help reduce or overcome the challenges associated with machining Inconel® 718.  

The pictures below are from the same study.  These pictures demonstrate the benefits in machining also extend to the quality of the nickel 718 workpiece being machined. 

Halocarbon MWF:  Finished machined test articles that utilized Halocarbon MWF 32.

Competitive Fluid: Finished machined test articles that utilized Competitive Control Fluid (CCF).

Why are Machining Fluids the Often Forgotten Variable?

When engineers troubleshoot machining nickel 718, the focus often falls on tool geometry, coatings, or cutting parameters. Yet, as the data shows, cutting fluid choice can also deliver gains just as significant. The right fluid extends tool life, improves finish, and reduces cycle time—all without changing the tooling or the CNC program.

In this way, cutting fluids are the “forgotten variable” in the machining of difficult-to-machine alloys like nickel 718 — an overlooked lever that can deliver real productivity and real cost benefits.

Conclusion

Machining nickel 718 will always be a challenge, but Halocarbon MWFs make it more manageable. By reducing friction, controlling heat, and protecting tools, Halocarbon MWF32 proved in independent testing that it can outperform a leading competitor fluid.

Don’t forget that this is a lever at your disposal.  Consider optimizing ALL the variables, and include a Halocarbon MWF in your nickel 718 machining plan to unlock the Halocarbon advantage. 

Don’t Forget the Halocarbon Advantage

Halocarbon MWFs aren’t just another machining fluid—they’re a proven performance enhancer across the toughest alloys.