Surface Treatment for Lubrication

Surface Treatment for Lubrication

Surface treatments commonly used as alternatives to surface film depositions include thermal diffusion, ion implantation, and chemical conversion coatings.

(a) Thermal diffusion: This is a process that introduces foreign atoms into a surface for various purposes such as increasing wear-resistance by increasing surface hardness; producing low shear strength to inhibit scuffing or seizure; and in combination with these to enhance corrosion-resistance.

(b) Ion implantation: This is a recently developed method that bombards a surface with ions to increase hardness, which improves wear- and fatigue-resistance.

(c) Chemical conversion coatings: Frequently, solid lubricants will not adhere to the protected metal surface. A conversion coating is a porous nonlubricating film applied to the base metal to enable adherence of the solid lubricant. The conversion coating by itself is not a suitable lubricant.

(4) Polymers: Polymers are used as thin films, as self-lubricating materials, and as binders for lamellar solids. Films are produced by a process combining spraying and sintering. Alternatively, a coating can be produced by bonding the polymer with a resin. Sputtering can also be used to produce films. The most common polymer used for solid lubrication is PTFE The main advantages of PTFE are low friction coefficient, wide application range of -200 to 250C (-328 to 418F), and lack of chemical reactivity. Disadvantages include lower load-carrying capacity and endurance limits than other alternatives. Low thermal conductivity limits use to low speed sliding applications where MoS₂ is not satisfactory. Common applications include antistick coatings and self-lubricating composites.