Additives
TLT Sounding Board November 2026
Executive Summary
About a third of TLT readers report they have had to reformulate additive packages for emerging alloys in the past two years, with extreme pressure (EP) additives cited most often as the most critical property. Phosphorus-based EP additives and phosphate esters remain the go-to for machining titanium alloys, γ-TiAl and advanced high-strength steels, while bans on chlorinated paraffins are pushing formulators toward ashless alternatives. Looking ahead, readers see the greatest need for development in additive chemistries tailored to new alloys' oxide layers and surface energies, plus more fundamental compatibility studies before scale-up.
Q.1. Please describe a case where lubricant additives played a critical role in machining, forming or processing new or emerging alloys (e.g., high-entropy alloys, titanium aluminides, advanced steels).
Additively manufactured (3D printing) aerospace components, including TI-6AI-4V titanium and Inconel 718, have provided challenges and require greater study and possible rebalancing of formulation to ensure meeting critical finished machining requirements.
Deep drilling and honing of new Ti alloys, also high Si-Al-Mg alloys.
EP additives in metalworking fluids play key roles in machining of hard-to-machine alloys. Without proper additives, workpieces including engine materials can't be well processed, causing materials wear and surface finish problems, as well as tool damages, e.g., deep drilling tools.
Sulfurized fat serves as an indispensable and critical additive in metalworking fluids.
390 aluminum transmission valve body machining. Aluminum cylinder head reaming operation with Mapal tools. Magnesium machining with water base coolant.
One representative case involved the machining of TB6, an advanced beta-titanium alloy used for highly loaded aerospace components. The alloy is difficult to machine because its high strength, low thermal conductivity and chemical affinity for cutting-tool materials produce high interface temperatures, adhesion, rapid tool wear and unstable surface quality. Water provides effective cooling, but insufficient boundary lubrication, while conventional hydrocarbon lubricants such as paraffinic oil and PAO may fail to form a sufficiently strong film on freshly exposed titanium surfaces. The solution was a water-based lubricant containing a self-emulsifying ester combined with an organic phosphate ester additive. The self-emulsifying ester improved wetting and created a physically adsorbed lubricating film. The phosphate ester provided additional load-carrying capacity by interacting with the titanium surface and forming a chemically adsorbed boundary layer containing P–O–Ti bonds. This combination was critical: water removed heat, the ester improved film formation and the phosphate additive protected the tool–workpiece interface under high pressure. The practical result of an appropriately designed additive package is longer tool life, more consistent surface finish, reduced scrap and the possibility of increasing machining productivity. The main lesson is that for emerging and difficult-to-process alloys, the lubricant additive is often a functional part of the manufacturing process rather than simply an auxiliary consumable.
Cases of EP lubricants can be studied where additives interact with high temperature and pressure. In this way we can use metal lubricants and their additives.
A compelling case where lubricant additives played a critical role involves the high-performance machining and turning of intermetallic gamma titanium aluminides (γ-TiAl). This emerging class of aerospace and automotive alloys offers exceptional heat resistance and low density but is notoriously "difficult-to-cut" due to its brittle nature, poor ductility and low thermal conductivity.
During the forming of advanced high strength steels (AHSS) for automotive components, lubricant additives were essential to prevent galling and reduce die wear under extremely high contact pressures. A lubricant formulated with phosphorus-containing EP additives and friction modifiers created a protective boundary film on tooling surfaces. This reduced friction, improved material flow, extended die life and enabled the successful forming of complex geometries without surface defects. The additive technology was a key enabler for manufacturing lightweight vehicle structures using next-generation steel grades.
Has your organization had to adjust or reformulate lubricant additive packages to accommodate the processing of new/emerging alloys in the past two years?
Yes
38%
No
62%
Based on an informal poll sent to 15,000 TLT readers.
Q.2. What specific challenges have you encountered when selecting or adapting lubricant additives for compatibility with novel alloy systems, and how were they addressed?
The challenges lie in lubricity, cooling and flushing out the chips. I understand the requirements, but we do not have much market requirements for these.
Currently working on developing a high-performance machining option for 3D printing of high-performance materials for the aerospace industry.
Regulations banning or limiting the use of chlorinated paraffins which are useful to machining of titanium alloy.
Whether the formulated additives meet the operating conditions for machining new alloys can be a challenge. Fundamental studies of compatibility of additive candidates with new alloys are necessary.
How to improve the processing efficiency while protecting the quality of the metal surface during the processing of aluminum alloy? This requires the use of a combination of corrosion inhibitors and lubricants.
The main challenge I have encountered is that additive systems proven in conventional steel applications do not necessarily provide the same performance on titanium alloys, high-alloy steels or other novel materials. These alloys have different oxide layers, surface energies, thermal conductivities and chemical affinities. As a result, a traditional sulphur-, phosphorus- or zinc-containing additive may either fail to form an effective boundary film or become excessively reactive, causing staining, corrosion, deposits or deterioration of the surface finish. Another difficulty is balancing lubricity with the overall stability of the formulation. Lubricant additives for novel alloys must be selected according to the specific surface chemistry and manufacturing process; simply increasing the concentration of a conventional additive package rarely provides a reliable solution.
Additive structures are adapted by modifying the polar functional groups to increase adsorption affinity for the specific oxides of the new alloy. For example, using ashless phosphorus-nitrogen compounds or organic acid derivatives that chemically adsorb onto aluminum or titanium oxides at lower activation energies.
A challenge involved forming operations on AHSS, where traditional lubricants lacked sufficient load-carrying capacity under extreme contact pressures. This was addressed by optimizing the additive package through a combination of phosphorus-based EP additives and boundary lubricity enhancers, which improved die protection and reduced galling without negatively affecting downstream welding or coating processes.
Which additive function has posed the greatest performance or compatibility challenge in processing advanced alloys?
Extreme pressure (EP) additive
60%
Antiwear additive
33%
Friction modifier
20%
Corrosion inhibitor
40%
Boundary lubrication enhancer
33%
Other
7%
Based on an informal poll sent to 15,000 TLT readers. Total exceeds 100% because respondents were allowed to choose more than one answer.
Editor's Note: Sounding Board is based on an informal poll sent to 15,000 TLT readers. Views expressed are those of the respondents and do not reflect the opinions of the Society of Tribologists and Lubrication Engineers. STLE does not vouch for the technical accuracy of opinions expressed in Sounding Board, nor does inclusion of a comment represent an endorsement of the technology by STLE.