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Hygroscopic moly disulfide

Hygroscopic moly disulfide

Hygroscopic moly disulfide

Has anyone any experience of molybdenum disulfide (MoS2) dry lube, in its baked (heat-polymerized) version, taking up humidity from humid atmospheres, thereby increasing its friction coefficient ? Increase in apparent friction factor during fastener torque/tension characterization tests has been experienced, although this may be due to film breakdown in humid conditions under the high point loads involved.


RE: Hygroscopic moly disulfide

Take a look at the NASA publications that Kenneth provides links to in thread 404-32366.  Very good discusion of wet atmosphere effects on MoS2.  Also, book by A.R. Lansdown, entitled "Molybdenum Disulphide Lubrication" (Elsevier Tribology Series, 35, 1999).

RE: Hygroscopic moly disulfide

Thanks for the tip TEV

Kenneth, any chance of getting your NASA link in thread 404-32366, TEV mentioned this link, but I have no access to it as Keyword search is down.

RE: Hygroscopic moly disulfide

Yates - with my regards to Kenneth, I have copied his posting from thread 404-32366 and added a star to it for you:

From Kenneth:

NASA SP-8063: http://mtrs.msfc.nasa.gov/mtrs/71/sp8063.pdf
(See Section and Table VI)  Excerpt: "There are bonded solid lubricants ... which combine relatively small quantities of graphite with major portions of MoS2.  There behavior in vacuum is dominated by MoS2, and they perform satisfactorily with respect to friction."

NASA/TM-1999-107249, Chapter 7
Aerospace Mechanisms and Tribology Technology:
Case Studies: http://gltrs.grc.nasa.gov/reports/1999/TM-1999-107249-CH7.pdf
(See Sections and

Friction and Wear Properties of Selected Solid Lubricating Films
Part 1: Bonded and Magnetron-Sputtered Molybdenum Disulfied and Ion-Plated Silver Films
(See Conclusions)

NASA/TM-2000-107249/Chapter 6
Solid Lubrication Fundamentals and Applications Friction and Wear Properties of Selected Solid
Lubricating Films: Case Studies: http://gltrs.grc.nasa.gov/reports/2000/TM-2000-107249-CH06.pdf
(See Table 6.2)

Durability Evaluation of Selected Solid Lubricating Films
(See Experimental Results and Discussion)

Metals Handbook, Volume 18: Friction, Lubrication, and Wear Technology:

"In spite of its desirable crystal structure, graphite is not an intrinsic solid lubricant.  It lubricates in are but fails to lubricate at high temperatures or in vacuum.  Savage (Ref 21) reported convincing experimental evidence that graphite must absorb moisture or other condensable vapor such as hydrocarbons in order to be lubricative.  The model appeared to be substantiated by the observation that, even in the presence of condensable vapors, graphite failed to lubricate above the desorption temperature.

However, Peterson and Johnson (Ref 10) observed that graphite again becomes lubricative at high temperatures when the lubricated metal becomes visibly oxidized... The authors postulate that restoration of lubrication ... was due to interaction of graphite with oxides of the metal.  The surface oxides were thought to promote adhesion of the graphite to the lubricated surfaces.  The maximum temperature for lubrication with graphite films is limited by oxidation to about 550°C (1020°F)."

RE: Hygroscopic moly disulfide

Yates:  The original thread was by Boomerang, entitled "PTFE Graphite Molybdenum Disulphide".  It is about the 25th thread down in the Mechanical Engineering Other Topics forum.  It is quite lengthy.  Sorry I didn't include this in my original post.  I couldn't find it, but I have since learned how.  I am somewhat new to this site and an still learning my way around.

You chould also note that Kenneth states in a later post in the same thread that the first link is dead, and he gives another link to the same material.

RE: Hygroscopic moly disulfide

You can create links to other posts.  In this case:


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