Laser Cutting Titanium: Inert Gas, Alpha Case, and Edge Control

Titanium's reactivity is the central fact of cutting it. Above roughly 600°C it absorbs oxygen, nitrogen, and hydrogen aggressively, and the hot edge of a laser cut sits well above that. Unshielded, the edge forms alpha case — a hard, oxygen-enriched, brittle surface layer — and discolors from straw to blue to grey, each color signaling deeper contamination. That brittle layer is a fatigue-crack initiation site, which is unacceptable in the aerospace and medical parts titanium is bought for. The answer is inert assist and shielding gas. Argon is commonly used to both eject the melt and blanket the cut from atmospheric pickup. Some shops add trailing shields or argon back-purge on the underside. Done right, the edge stays bright or shows only the faintest tint. The practical takeaway: never let a shop cut your structural titanium without a deliberate inert-gas strategy, and ask how they verify the edge.

Grade 2 is commercially pure titanium — ductile, weldable, corrosion-resistant, and the most forgiving to cut. It's the workhorse for chemical, marine, and architectural parts and tolerates the laser's thermal cycle well. Grade 5 (Ti-6Al-4V) is the aerospace alloy: roughly twice the strength, but its two-phase alpha-beta microstructure is more sensitive to the rapid heating and cooling at a laser edge, and contamination embrittles it more severely. Grade 23 is Ti-6Al-4V ELI (extra low interstitial), used in medical implants where fracture toughness and biocompatibility are paramount. Its whole reason for existing is low interstitial oxygen content — which makes oxygen pickup at a laser edge especially counterproductive. For Grade 23 implant work, edge contamination control is non-negotiable and many parts get the laser edge removed by post-machining or chem-milling. The honest summary: Grade 2 cuts easily, Grade 5 cuts well with care, and Grade 23 demands the tightest process control of the three.

Titanium's lower thermal conductivity than aluminum actually helps the laser keep heat in the kerf, so it cuts at reasonable speeds. Fiber lasers handle titanium well from foil up to roughly 12-15 mm depending on power. Tolerances mirror other metals — about ±0.1 mm on thin stock, opening with thickness — and edges are clean when shielding is good. The finishing story is where titanium differs. Because the laser edge can carry alpha case and HAZ, critical parts often specify removal of that layer: light machining, grinding, or chemical milling that strips the affected skin. For fracture-critical aerospace and all implant work, this is standard practice. If your part is non-critical (a bracket, a non-loaded panel), the as-cut shielded edge may ship as-is. Knowing which category your part is in determines whether you're buying a finished blank or a part that needs a post-cut conditioning step.

Titanium is expensive material, and the cutting adds inert-gas cost and tighter process control on top. Expect titanium laser parts to cost several times their stainless equivalents, with Grade 23 implant work the priciest because of material grade, ELI certification, and edge conditioning. Lead times run longer too — material is often ordered to cert, and AS9100 or ISO 13485 documentation adds administrative time. Waterjet is the honest alternative for fracture-critical titanium. Because it's a cold cut, waterjet creates no HAZ and no alpha case — the edge is metallurgically untouched. For thick titanium, for implant-grade parts where any contamination is disqualifying, and for low quantities where the inert-gas setup isn't worth it, waterjet frequently wins. Laser keeps its edge on thinner titanium, higher volumes, and parts where the slightly faster cut and tighter feature tolerance justify the contamination-control effort.