Drilling Inconel 718, a high-strength, heat-resistant nickel alloy, presents a unique challenge due to its hardness, toughness, and tendency to work-harden during machining. To achieve optimal results, you need to use specialized drills designed for high-temperature alloys. Below are the best drills and tips for drilling Inconel 718:
Best Drills for Inconel 718:
Carbide Drills (Solid Carbide):
Why: Carbide drills are ideal for hard metals like Inconel 718 because they maintain their hardness even at high temperatures. They are highly wear-resistant and provide excellent performance in tough, heat-resistant alloys.
Tip: Use carbide drills with a coated surface (such as TiAlN or TiCN coating) for enhanced wear resistance and heat resistance.
Recommended Use: Solid carbide drills are best suited for drilling applications where high precision and tool longevity are required.
Cobalt Drills:
Why: Cobalt drills are another good choice for drilling Inconel 718, as they have high heat resistance and are tougher than regular high-speed steel (HSS) drills.
Tip: Cobalt drills, especially M35 or M42 grades, provide a good balance of strength, heat resistance, and toughness. However, they are not as wear-resistant as carbide.
Recommended Use: Cobalt drills are suitable for medium-precision applications and can handle the heat generated while drilling.
High-Speed Steel (HSS) Drills with Coatings:
Why: HSS drills are less durable for Inconel 718 compared to carbide or cobalt, but they can be used if coated appropriately. TiN (Titanium Nitride) or TiAlN coatings significantly improve the lifespan of HSS drills.
Tip: If using HSS drills, ensure proper cutting parameters such as feed rate and cutting speed to avoid overheating and premature wear.
Drilling Tips for Inconel 718:
Cutting Speed:
Use low cutting speeds for Inconel 718, typically in the range of 20-30 SFM (Surface Feet per Minute). Inconel 718 is prone to work hardening, so high speeds can lead to rapid tool wear.
Coolant:
Use abundant coolant (preferably high-pressure coolant) to reduce heat generation and improve tool life.
Use wet drilling with high-pressure lubrication or minimum quantity lubrication (MQL) to keep the tool cool and lubricated.
Peck Drilling:
In deep hole drilling, use the pecking method (breaking the hole into smaller, shallow cuts) to minimize heat buildup and reduce the risk of work hardening.
Drill Geometry:
Use drills with a sharp point angle (118° or 135°) and a positive rake angle to help reduce cutting forces and heat generation.
Consider using split-point drills for better centering and reduced walking.
Feed Rate:
Use a low feed rate to avoid overloading the tool and to prevent excessive heat buildup.
Drill Size:
Start with smaller drills for initial holes, then gradually increase the size to reduce pressure on the drill bit and improve precision.
Top Brands and Tools:
Kennametal: Known for their high-performance carbide drills for tough materials like Inconel 718.
Walter Tools: Offers carbide drills designed specifically for heat-resistant alloys.
Seco Tools: Provides advanced drills with coatings and geometries for high-performance drilling in difficult materials like Inconel.
Sandvik Coromant: Their range of carbide drills, with specialized coatings, is optimized for drilling tough metals.
Conclusion:
The best drill for Inconel 718 would be a solid carbide drill with a coating (like TiAlN) for high wear resistance and heat management. Cobalt drills can be a good option for less critical applications, while HSS drills with coatings are a cost-effective alternative for certain operations. Always ensure the correct cutting parameters and use high-quality coolant to extend tool life and achieve optimal results.
