45NCD17 is the French AFNOR designation for a high-strength nickel-chromium-molybdenum tool and structural steel, carried in Germany as DIN X45NiCrMo4 (also written 45NiCrMo16) and Werkstoffnummer 1.2767, and cross-referenced in Britain to grade 6F7. With roughly 0.45% carbon and a substantial nickel addition around 4%, plus chromium and molybdenum in supporting amounts, this is fundamentally a deep-hardenability alloy: the nickel promotes toughness and pushes hardenability well into thick sections, the chromium contributes wear resistance and hardenability, and the molybdenum resists temper embrittlement while adding secondary hardness.

That combination of high strength, excellent toughness, and reliable through-hardening in large sections is what makes 45NCD17 a go-to grade for heavy-duty dies, punches, forging tools, and structural tooling components that need to resist both wear and shock loading without failing brittlely. It responds to a broad tempering range (roughly 200-600°C) to dial in anywhere from very high hardness with lower toughness to a more moderate hardness with maximum toughness, which gives toolmakers real flexibility in matching the heat treatment to the specific duty cycle of the part.

45NCD17 is typically supplied and machined in a pre-hardened or quenched-and-tempered condition rather than fully annealed, since the whole point of the alloy is deep hardenability — leaving it dead soft would waste the nickel-driven toughness the grade is chosen for. In the commonly supplied condition (roughly 38-45 HRC), machining forces run noticeably higher than an annealed carbon or low-alloy steel, and the toughness that makes this grade valuable in service also makes it somewhat gummy to cut: chips can be tougher to break than in a more brittle tool steel, so chip control and rigid tool geometry matter more than raw hardness alone would suggest.

Coated carbide grades with good hot hardness and edge toughness perform best, since heat generated at the cutting edge builds quickly in this nickel-rich matrix. Moderate cutting speeds, positive rake geometry where possible, and adequate coolant to manage both temperature and chip evacuation are the standard approach. Because the material is usually finish-machined at or close to final hardness, dimensional stability during cutting and minimizing built-up edge are bigger concerns here than they are with a soft, annealed tool steel.

Speeds below are for the commonly supplied pre-hardened condition (~38-45 HRC).

Milling

Turning, parting, and grooving grade recommendations for 45NCD17 are not on file for this material yet. Browse the full turning/parting collection below for a grade suited to your hardness and finish requirements.