Nickel Alloy
CNC Machining

Nickel-based superalloys (including Inconel 625, Inconel 718, Hastelloy C-276, and Monel 400) are high-performance alloys based on nickel as the primary element, engineered for extreme heat resistance, corrosion resistance, and mechanical strength at elevated temperatures. They are significantly more difficult to machine than stainless steel or titanium because they work-harden rapidly under cutting forces, have very low thermal conductivity that concentrates heat at the tool tip, and contain hard carbide and intermetallic phases that cause rapid abrasive tool wear. Cutting speeds for nickel alloys are typically 10–30% of those used for stainless steel.

Both are nickel-chromium superalloys but with different strengthening mechanisms and applications. Inconel 625 (UNS N06625) is solution-strengthened with niobium and molybdenum — it has outstanding corrosion resistance, excellent weldability, and good strength at high temperatures, but is not age-hardenable. Inconel 718 (UNS N07718) is precipitation-hardened by niobium and aluminum additions — it has significantly higher tensile strength (up to 1380 MPa in aged condition) and fatigue resistance, making it the dominant aerospace and turbine superalloy. Inconel 718 is harder to machine than 625 due to its higher strength and work-hardening tendency.

Hastelloy C-276 (UNS N10276) is a nickel-molybdenum-chromium alloy engineered specifically for maximum corrosion resistance in aggressive chemical environments. It offers superior resistance to oxidizing acids (nitric, chromic), reducing acids (hydrochloric, sulfuric), and mixed acid conditions — outperforming both Inconel 625 and stainless steel in many chemical service environments. Specify Hastelloy C-276 when the primary requirement is chemical corrosion resistance, especially in chloride-containing, acidic, or mixed oxidizing/reducing environments. For high-temperature aerospace or turbine applications, Inconel 718 is the correct choice.

Monel 400 (UNS N04400) is a nickel-copper alloy (approximately 67% Ni, 31% Cu) — the simplest and oldest commercial nickel alloy. Unlike Inconel (nickel-chromium) and Hastelloy (nickel-molybdenum-chromium), Monel 400 derives its corrosion resistance primarily from the nickel-copper system. It has exceptional resistance to seawater and brine, hydrofluoric acid, and alkaline environments, and is the most machinable of the four alloys. Monel 400 is specified for marine hardware, pump shafts and impellers in seawater service, heat exchanger tubing, and chemical handling equipment — particularly where hydrofluoric acid resistance is required.

Standard tolerance for nickel alloy CNC turning and milling is ±0.02 mm. For precision features (bores, shaft diameters, sealing faces), we hold ±0.010–0.015 mm. Note that nickel alloys spring back more than steel after cutting — particularly Inconel 718 — so final tolerances on tight-fit features require careful process control. CMM inspection reports are provided for all precision nickel alloy components. Tighter tolerances (±0.005 mm) are achievable on selected features with process confirmation — please specify in your drawing.

Nickel alloys require premium cutting tools not used on standard steel or aluminum jobs. We use coated carbide inserts (PVD TiAlN and AlTiN coatings) for general turning and milling, ceramic inserts (SiAlON and whisker-reinforced alumina) for high-speed roughing of Inconel 718, and PCBN (polycrystalline cubic boron nitride) for finishing cuts on hardened Inconel 718. High-pressure coolant (70–100 bar) is directed at the cutting zone on all nickel alloy operations. Tool life is monitored and inserts are changed at defined intervals regardless of visible wear.

Use Inconel 625 for seawater, chemical, and cryogenic applications where corrosion resistance and weldability are primary requirements. Use Inconel 718 for aerospace, turbine, and high-temperature structural applications where maximum strength and fatigue resistance are required. Use Hastelloy C-276 for the most aggressive chemical environments — mixed acids, chloride solutions, and chemical reactors where Inconel 625 would corrode. Use Monel 400 for marine hardware, HF acid service, and applications where a lower-cost, easier-to-machine nickel alloy is acceptable. If unsure, share your operating temperature, fluid or chemical exposure, and mechanical load — we will recommend the correct grade before quoting.

Yes. All nickel alloy orders are supplied with material test reports (MTR) including chemical composition and mechanical properties per the relevant standard: ASTM B446 for Inconel 625, AMS 5662/5664 or ASTM B637 for Inconel 718, ASTM B574 for Hastelloy C-276, and ASTM B164 for Monel 400. Heat number traceability is maintained throughout production. For aerospace and safety-critical applications, full first article inspection (FAI) reports and dimensional CMM reports are available on request.