New TA18 Study Moves Hot Extrusion From Friction Control to Interface Design

A paper made available online by Tribology International on July 22, 2026 gives titanium tube buyers a more precise way to think about hot-extrusion lubricant. The researchers developed a boron-free silicate glass for TA18 titanium and reported a coefficient of friction below 0.1 from 750°C to 850°C—79% lower than dry sliding under their test conditions.

The important result is not the number alone. The glass did more than soften and separate two sliding surfaces. Calcium in the glass reacted with the TiO2-rich oxide layer on TA18 and precipitated CaTiO3 micro-protrusions at the interface. Those features acted as anchors, improving wetting and bonding so the lubricating film resisted dewetting and delamination under shear.

That mechanism changes the industrial question. High-temperature lubrication is not only a consumable choice or a friction coefficient. It is a temporary interface engineered among the billet surface, oxide, glass chemistry, die, temperature and deformation schedule. If one element moves outside the validated range, a laboratory friction value cannot describe the actual extrusion.

The Lubricant Works Through The Oxide, Not Around It

TA18 is a near-alpha Ti-3Al-2.5V alloy used for tubular applications. The paper examined TA18 discs against hot-work die-steel pins at 750°C, 850°C and 950°C. Its low-alkali aluminosilicate glass used ZnO to reduce reliance on alkali oxides and was designed without volatile boron compounds. The authors reported a softening temperature near 660°C and negligible mass loss below 0.2% up to 850°C.

At 850°C, the interface supplied the clearest explanation for film stability. Ca2+ from the glass reacted with TiO2 in the surface oxide to form CaTiO3. The resulting ceramic–glass architecture combined an easily sheared glass phase with small reaction products that increased attachment and load support. The film therefore stayed useful because a controlled reaction occurred, not because the glass remained chemically inert (paper).

This is the industry mechanism: in hot titanium forming, the oxide layer can become a functional part of lubrication. The correct objective is not to remove every reaction. It is to control which reactions occur, where they occur and whether their products help forming without creating an unacceptable surface or cleaning burden.

The study also sets a necessary boundary. It reports strong performance from 750°C to 850°C in a defined pin-on-disc system. It does not prove that the same glass, coating mass or interfacial reaction will remain optimal at every billet size, extrusion ratio, die geometry, speed or atmosphere. It also does not qualify a production tube for an aerospace hydraulic system.

A Low Friction Number Is Not A Tube Release Record

Hot extrusion connects several outputs that procurement often separates. Lubrication influences die contact, metal flow, extrusion load, surface pickup and tool wear. Those effects can then appear as dimensional variation, laps, scoring, embedded residue, oxide scale or extra material removal.

A supplier can therefore show a low laboratory coefficient while still lacking evidence that the full route produces acceptable tube. The buyer needs to know how the lubricant is mixed and applied, how long the coated billet waits before forming, where billet and die temperatures are measured, whether extrusion force remains stable, and how the finished surface is cleaned and inspected.

The opposite shortcut is also risky: treating all reaction products as contamination without examining their location and removal. CaTiO3 formed at the tribological interface helped the tested film remain attached. Whether any reaction product remains on a production tube, and whether it matters, depends on the subsequent descaling, pickling, machining, inspection and end-use specification. That decision must be made on the real product route, not inferred from a microscopy image in a paper.

A Five-Zone Lubricant-To-Tube Map

Before a high-temperature lubrication change enters recurring titanium tube production, five zones should agree.

The map keeps a development result in its proper place. Tribology screening can identify a promising temperature–chemistry mechanism. Production validation must then show that the mechanism survives scale, geometry and operating variation.

What Tube Buyers Can Use Now

The paper gives suppliers a useful development direction: evaluate wettability, interfacial reaction and film attachment together instead of optimizing viscosity or friction in isolation. A lubricant that flows well but pulls away under shear may fail. A strongly bonded film that cannot be removed or that damages the surface may create a different problem.

For buyers of titanium tubes, the practical request is a route record, not the paper’s glass recipe. Specify the required alloy, dimensions, condition, surface and inspection basis. Then ask the supplier to show that its forming and lubrication window can repeatedly meet them. If the route includes pickling and alpha-case removal, define how material removal, final wall tolerance and surface acceptance remain connected.

Change control matters because the effective interface contains more variables than the lubricant trade name. A new glass batch, altered particle size, slurry ratio, coating thickness, billet surface, preheat time, die coating or extrusion speed can change film formation and reaction. The supplier should know which changes remain within routine control and which require trials, additional inspection or customer review.

The restrained conclusion is that reaction-induced self-anchoring is a credible explanation for the reported TA18 performance, not a universal production approval. Its durable value is the shift in purchasing logic: hot-extrusion lubrication should be controlled as an interface system, and a titanium tube should be released only when that interface, the forming record and the final surface tell the same story.

Industry FAQ

What did the 2026 TA18 lubrication study report?

The study reported a coefficient of friction below 0.1 from 750°C to 850°C with a boron-free silicate glass, 79% lower than dry sliding under the tested conditions.

Why did the glass film remain attached to TA18?

Calcium in the glass reacted with titanium oxide to form CaTiO3 micro-protrusions that improved wetting and interfacial bonding, helping resist dewetting and delamination.

Does the study qualify a lubricant for production titanium tubes?

No. It used a defined laboratory tribology system. Production extrusion still needs validation for the billet, die, temperature, reduction, coating method, cleaning route and tube requirements.

What evidence should a titanium tube buyer request?

Ask for the controlled forming temperature, lubricant identity and application, extrusion load or stability records, surface and dimensional inspection, cleaning or alpha-case removal, and change-control rules.