Grade 6 Titanium CNC Machining Services — Ti-5Al-2.5Sn (UNS R54520)

Engineering Challenge

Grade 6 is used in high-temperature service where any oxygen pickup from welding, grinding, or aggressive machining reduces fatigue life and can crack under thermal cycling. The hard, brittle oxygen-enriched surface layer (alpha case) must be removed by chemical milling or controlled pick-pass machining before service.

Our Machining Approach

We confirm the material condition and any prior thermal exposure at incoming inspection. Cutting parameters are tuned to keep the cutting-zone temperature well below the alpha-case formation range, with high-pressure coolant and conservative engagement. Where the customer specification requires chemical milling, we schedule the pickling step per ASTM B600 / AMS 2402 between rough and final machining.

Engineering Outcome

Bulk mechanical properties consistent with the agreed specification, with the alpha case removed from machined surfaces before shipment.

Engineering Challenge

Alpha titanium has a low elastic modulus (~110 GPa) and limited work-hardening response. Thin-wall and slender features in Grade 6 deflect under cutting forces and recover elastically after the tool passes. The same drawing features that work for GR5 (stiffer) often need different sequencing for GR6 to hit the same tolerance band.

Our Machining Approach

We use balanced roughing and finishing sequences, dedicated workholding sized to the part envelope, and conservative engagement on thin-wall features. In-process measurement catches deflection between roughing and finishing, so geometry drift can be corrected before final pass.

Engineering Outcome

Thin-wall features held within drawing tolerance at the agreed strength level. For suitable validated geometries, the process can target linear dimensional tolerance up to ±0.025 mm — project-specific targets, not universal guarantees.

Engineering Challenge

In addition to machining-induced alpha case, the same risk exists from any subsequent grinding, welding, or post-machining heat treatment. Surface roughness alone does not establish fatigue performance or thermal-cycling resistance; sub-surface alpha case can seed crack initiation at high temperature.

Our Machining Approach

We schedule ASTM B600 alkaline cleaning + acid pickling for components that go into high-temperature service. For very tight fatigue / creep requirements, light pick-pass machining removes 0.05–0.10 mm of surface material to eliminate the alpha case after heavy machining.

Engineering Outcome

Surface free of alpha case and embedded contamination, with documented surface-finish values and pickling records.