1	DYNAMIC COATINGS, INC. Solid & Bonded Film Lubricants
2	Common Lubricating Solids Molybdenum disulfide (MoS₂) Graphite PTFE (polytetrafluoroethylene) Nylon
3	Molybdenum Disulfide (MoS₂) Used in resin & inorganic binder coating systems Advantageous when low concentrations of lubricant are required on highly finished surfaces Limited to 750º F. in oxidizing atmospheres Higher operating temperatures are feasible when oxygen is not present
4	Molybdenum Disulfide (MoS₂) MoS₂ has strong planar bonds The interatomic forces between planes (Van der Waals) are weak causing low shear No free electrons – dielectric or semi-conductive Hardness is 1 to 1.5 on the MOH’s scale
5	Molybdenum Disulfide (MoS₂) Does not require moisture vapor Dry atmospheres optimize COF performance COF measures as low as .07 under load and sliding velocity of 1500 ft./min. Sliding load capacity: Dry – upwards to 50,000 psi Wet – upwards to 200,000 psi Rolling load capacity is approximately 300,000 psi Class 1 material – non-toxic
6	Graphite In graphite each carbon atom is covalently bonded (localized) to 3 other carbon atoms in the flat or planar structure The 4^th valence election is non-localized (mobile). This permits graphite to conduct electricity Graphite measures 1 to 2 on the MOH’s scale (soft!)
7	Graphite Used in resin & inorganic binder coating systems Applicable when electrical conductivity is important Better properties than molybdenum disulfide above 750º F. (up to +1200º F.) Generally is not suitable in vacuum
8	Graphite Low friction develops only in the presence of moisture vapor volatile organic material Complete oxidation produces carbon dioxide (Co₂) gas with no abrasive residue and occurs at about 2000º F. COF measures as low as .15 under load and moderate velocity Sliding load bearing capacity: Dry – upwards to 25,000 psi Wet – upwards to 100,000 psi Rolling load capacity is much higher – nearly double Class 1 material – non-toxic
9	PTFE (polytetrafluoroethylene) PTFE is a linear long chain molecule [C₂F₄]_N. The CF₂ groups are equally spaced along the chain which is twisted to form a helix twist of 180º. Particles produced by dispersion polymerization are in the order of .02 microns; particles produced by granular polymerization are several hundred microns and higher in molecular weight
10	PTFE (polytetrafluoroethylene) Used in resin & inorganic binder coating systems Is almost completely inert; Has a very low surface energy with little tendency to bond to other materials Excellent for loads less than 5,000 psi, but not as good as graphite or MoS₂ at higher loads Static & Dynamic COF are equal and about the same as wet ice on wet ice Is not wetted by and does not absorb water. Unaffected by acid, bases & solvents normal to industry Working temperature range from -423º F. to 482º F. (250º C.); Only above 752º F. (400º C.) is degradation significant
11	Application Methods of Common Lubricated Solids What are Application Methods? These include: Incorporation into base material as a composite Burnish powder into substrate Apply grease or oil fortified with lubricating solids Replenishment systems using lubricating solids or grease/oil fortified with lubricating solids Impinge/Impact lubricating solids into porosity/surface irregularities of substrate surfaces being treated Pre-coat parts with adhesive resin-bonded films containing lubricating solids
12	Why use Solid Lubricants? Resistance to penetration by surface peaks under extreme loads Ability to shear more easily than the substrate material Most common and practical are molybdenum disulfide, graphite, PTFE (polytetrafluoroethylene), and nylon
13	Solid & Bonded Film Lubricants Simple Definition Solid materials with inherent lubricating properties which are firmly bonded to the surface of a substrate by some method
14	Solid & Bonded Film Lubricants These materials are essentially “lubricating paints” which typical formulations consist of: Lubricating solids (i.e. MoS₂, graphite, PTFE) Binder most binder systems use various aromatic solvents or water carriers for application operations ONLY! Solvents or Water Note: These do not add to performance and are eliminated during the cure cycle. Additives
15	Solid & Bonded Film Lubricants When should you use them? When other types of lubricants … Are likely to degrade or decompose at high temperatures or under high radiation fluxes Tend to solidify or congeal at low temperatures Volatize in high-vacuum or pressure environments
16	Solid & Bonded Film Lubricants When should you use them? More common reasons would include … Where fluids are likely to attract dust and lint Where adjacent parts must not be contaminated with fluids Where components are inaccessible for re-lubrication or are likely to be run unattended Requirements for little or no maintenance
17	Solid & Bonded Film Lubricants Solid & Bonded Film Lubricants help address these more common features: Longer Wear Life Lower Friction Coefficients Corrosion Protection Chemical Resistance Withstand High Loads Anti-seize & Anti-galling Lower Torque Wide Temperature Ranges Nonstick and/or Release
18	Solid & Bonded Film Lubricants Assume the same shape – including peaks – as the substrate Has low shear strength which causes lubricant peaks to rapidly wear down Interface is quickly transformed to a fairly smooth low-friction surface
19	Solid & Bonded Film Lubricants
20	Recommended Surface Pretreatments for Solid Film Lubricants
21	Surface Pretreatments Have A Pronounced Affect On Solid Film Performance
22	Frictional Resistance of Metal-to-Metal Contact Related to the force required to sheer or deform the peaks of the rough surface New parts often require break-in period during which the peaks wear down Typically, the softer surface is plowed and galled by the harder surface Due to asperities, it’s estimated that only around 20% of the surface between two metal blocks are in contact. The shearing of asperities is reduced by lubricants which separate the surfaces of moving parts
23	Solid Friction Sliding friction is caused by: Interference or Asperities (surface roughness) Welding (minute or gross)
24	Friction Characteristic Comparisons
25	Friction Characteristic Comparisons
26	Friction Characteristic Comparisons
27	Friction Characteristic Comparisons
28	Friction Characteristics Friction vs. Load (graphite & MoS₂ only) Friction vs. Film Hardness Friction vs. Speed
29	Friction vs. Load (graphite & MoS₂ only)
30	Friction vs. Film Hardness
31	Friction vs. Speed
32	Fluid Friction Resistance to lamina flow is shear stress Shear stress is affected by: Fluid viscosity Effective area Velocity Shear stress is not affected by load Fluid friction is the cumulative effect of shear stress
33	Fluid Friction
34	Wear Life Characteristics Wear Life vs. Load Wear Life vs. Speed Wear Life vs. Film Thickness
35	Wear Life vs. Load
36	Wear Life vs. Speed
37	Wear Life vs. Film Thickness
38	Wear Life Characteristics Wear Life vs. Film Hardness Wear Life vs. Substrate Wear Life vs. Pretreatment Quality
39	Wear Life vs. Film Hardness
40	Wear Life vs. Substrate
41	Wear Life vs. Pretreatment Quality
42	Hydrogen Embrittlement (HE) Atomic hydrogen (H) is the only species capable of diffusing through steel & other metal Molecular hydrogen (H₂) does not diffuse through metal All steel above 40 HRC is subject to hydrogen embrittlement continues …
43	Hydrogen Embrittlement (HE) Embrittlement potential of pretreatments / coatings: Acid cleaning/pickling: HE is inherent in these processes, however, this form is reversible Zinc/manganese phosphate: HE is inherent in these processes, however, this form is reversible Electroplating: may cause atomic HE which may or may not be irreversible (i.e. delays to bake, bake time, etc.) ¹ Organic / Inorganic coatings: These DO NOT cause HE. The cure cycle inherent in these coatings causes hydrogen dispersal and helps relieve inherent HE from the cleaning / phosphate pretreatments ¹ Craig Willan, P.E., Time and Temperature Effects on the Embrittlement Relief of High Strength Steel
44	DYNAMIC COATINGS, INC. End of Presentation