What are dry film lubricants?

April 16, 2020

Introduction

Dry-film lubricants are materials that are used to reduce the friction between two mating surfaces that slide against each other without the need for oils and greases.

Typically, dry-film lubricants will be used when other lubricants such as grease and oil cannot be used due to temperature load, wear, migration and debris. In these conditions, traditional lubricants like oil or grease can undergo a state change and no longer provide protection, however, a dry-film lubricant will remain intact and provide continuous lubrication and protection.

What are dry film lubricants?

Primarily, there are two main types of dry-film lubricants, which are known as crystalline lattice (lamella) type structures such as Molybdenum Disulphide, Tungsten Disulphide and Graphite and Fluorocarbons such as PTFE.

In crystalline form structures such as Molybdenum (MoS2), the shear forces between opposing layers are weak resulting in lubricity between sliding surfaces.

There are several factors for PTFE coatings that define dry-film lubricants; firstly, the ability to resist attack from another chemical structure, secondly its bond strength, and lastly its ability to repeal other atoms which in combination gives PTFE coatings their ultra-low coefficient of friction and excellent chemical resistance.

What are dry film lubricants used for?

There is a wide variety of typical applications of dry-film coatings, some of which include:

• Fasteners, springs bearings, cams, gears and seals
• Aerospace hydraulic fittings, valve components and non-intrusive medical instruments
• Shafts, splines and bushes
• Rubber and other non-metallic substrates
• Saw blades and secateurs
• Automotive fasteners, seat slides and rails
• Petrochemical, oil and gas subsea and topside components

Dry-film lubricants are useful in conditions where conventional lubricants are inadequate.

One such example is where reciprocating motion is present. A standard application of dry-film lubricant could include where a sliding or reciprocating motion that requires lubrication to minimise wear is present. An example of this use case can be seen in gear and change lubrication. Liquid lubricants will squeeze out while solid lubricants will not escape interlocking or reciprocating parts.

Dry-film lubricants can also be used in ceramic applications for cases where chemically active lubricant additives have not been found for a particular surface, such as polymers or ceramics.

Also, the benefits of dry-film lubricants can be applied to instances where lubrication is required in a high-temperature environment or where there is an oxidising atmosphere. Liquid lubricants such as oil and grease will typically not survive these conditions.

Furthermore, where extreme contact pressures are present, dry-film lubricant provides a high bearing-load combined with a low shear stress due to the lamellar structure of the lubricant.

Application methods

Dry-film lubricants can be applied in a wide variety of methods to best suit the work-piece application and environment.

• Free powders
• Anti-frication coatings
• Spraying/ dipping/ brushing
• Composites

CWST has a proud history that dates back to 1920 when the Wright Brothers and Glen Curtiss founded the Curtiss-Wright Corporation. To find out more about Curtiss-Wright and the wide range of material finishing and treatment solutions click here or if you’d like to find out more about dry-film lubricants, visit our page about Everlube® coatings, or get in touch with a member of our team.