AL-6XN is a 6-Mo superaustenitic stainless steel, UNS N08367, built on a high-nickel (~24%), high-chromium (~20.5%) austenitic base with roughly 6.3% molybdenum and a nitrogen addition for strength and pitting resistance. The "6-Mo" name refers directly to that molybdenum level, which is roughly triple what 316 carries and is the single biggest driver of AL-6XN's outstanding resistance to pitting and crevice corrosion in chloride-rich environments. Its pitting resistance equivalent number (PREN) puts it well above 316 and even above most duplex grades, closer to the 6-Mo family that includes 254SMO and AL-6XN Plus.

That corrosion performance is what makes AL-6XN a standard material for seawater piping and heat exchangers, offshore and marine hardware, pulp and paper bleach plant equipment, flue gas desulfurization systems, and other chloride- or acid-heavy chemical processing service where 316 would eventually pit or crevice-corrode. Like other high-nickel austenitic grades it is fully austenitic and non-magnetic in the annealed condition and cannot be hardened by heat treatment — only cold work increases its strength.

AL-6XN is a proprietary alloy (Allegheny Technologies); UNS N08367 is its verified registered designation. Other cross-references were not confirmed and are omitted rather than guessed.

A nitrogen addition (typically ~0.2%) also contributes to strength and pitting resistance but could not be independently verified for this listing and is omitted.

AL-6XN machines like a more demanding cousin of 316: same fundamental austenitic behavior, but with more alloy content pushing cutting forces and tool wear higher across the board. Nickel content this high keeps the matrix soft and ductile rather than hard, but that ductility is exactly what makes it gummy — the material wants to smear and drag under the tool rather than shear cleanly, and it work-hardens rapidly wherever the edge rubs instead of cutting. Low thermal conductivity compounds the problem, concentrating heat at the cutting edge instead of letting it flow into the chip.

Sharp, positive-rake inserts with a chipbreaker geometry built for stainless are essential here; anything that lets the tool ride on the surface instead of biting in will leave a work-hardened skin that makes the next pass harder to cut. Feed rates need to stay firm and consistent for the same reason. Because the combined nickel-chromium-molybdenum content is well above 316, expect shorter tool life at any given speed than 316 unless the insert grade, coating, and rigidity are all dialed in — coolant and a rigid, well-supported setup matter more here than on lower-alloy stainless.

Values assume favorable conditions: a well-matched insert grade, rigid tool and workpiece clamping, good raw material quality, short tool overhang, and adequate coolant. Run toward the lower end of each range for AL-6XN given its high alloy content.

Turning

Parting / Grooving

Milling