Inconel / Nickel Superalloys Manufacturers & Suppliers

Inconel 718 work-hardens severely — a depth-of-cut below 0.010" can rub against an already-hardened surface layer rather than cutting, generating heat and causing rapid flank wear. Its thermal conductivity is approximately 11 W/m·K, concentrating heat at the tool tip rather than distributing it through the workpiece. The gamma-prime and gamma-double-prime precipitate phases that give 718 its strength are abrasive on carbide inserts at operating temperatures. Recommended practice involves ceramic inserts (SiAlON) for roughing at aggressive material removal rates with minimal coolant, and PVD-coated carbide for finishing with high-pressure flood coolant. Typical surface speeds are 50-100 SFM for carbide — roughly one-tenth of what aluminum demands.

Inconel 625 is a solid-solution-strengthened alloy: its strength comes primarily from niobium and molybdenum in the nickel matrix, requiring no aging heat treatment. It's specified where excellent weldability, corrosion resistance in aggressive media, and moderate strength to around 1500°F matter more than peak strength — offshore risers, chemical reactor cladding, and exhaust bellows. Inconel 718 is precipitation-hardened by gamma-prime and gamma-double-prime phases after solution anneal and double-age treatments, reaching nearly twice the room-temperature tensile strength of 625. Its use is concentrated in rotating engine hardware — turbine discs, compressor cases, fasteners — where the strength-to-weight advantage justifies the more complex heat treatment and more difficult machinability.

EDM wire cutting becomes the preferred process for Inconel when part geometry includes thin webs, narrow slots, or intricate profiles that would deflect under cutting forces, or when the hardened workpiece condition (40+ HRC equivalent) makes carbide tooling uneconomical. Because wire EDM removes material by electrical discharge rather than mechanical cutting, it imposes zero cutting force on the workpiece — critical for fragile features. The recast layer (typically 0.0001"–0.0005" thick) requires consideration for fatigue-critical aerospace parts, and post-EDM electropolish or gentle grinding may be specified to remove it. Wire EDM also produces excellent dimensional accuracy, routinely holding ±0.0002" on Inconel profiles.