Gallium useful bearing lubricant in high-vaccum environment

Solid gallium is used as a lubricant on bearings made of compatible materials. Such lubricants perform well in a high vacuum and under low temperature

Interaction of some extreme-pressure type lubricating compounds with an iron surface

An iron surface was exposed to the extreme-pressure type lubricant benzyl chloride, dichlorophenyl phosphine, dichlorophenyl phosphine sulfide, ophenyl phosphine oxide. Iron, in the sputter-cleaned state, was exposed to these materials statically and during dynamic friction experiments. With benzyl chloride only chlorine adsorbed to the surface, and with dichlorophenyl phosphine no adsorption occurred, while the addition of sulfur to that same molecular structure resulted in the promotion of carbon and chlorine adsorption. substitution of oxygen for sulfur in the dichlorobenzyl phosphine molecule resulted in carbon, chlorine, and oxygen adsorption. With none of the phosphorus containing molecules was phosphorus detected on the surface. Sliding in an atmosphere of benzyl chloride promoted adsorption of chlorine to the iron surface. Increases in load resulted in a decrease in the surface concentration of iron chloride

Auger spectroscopy analysis of lubrication with zinc dialkyldithiophosphate of several metal combinations in sliding contact

Sliding friction experiments were conducted with aluminum and other riders rubbing on disks of various elemental metals in the presence of a thin film of zinc dialkyldithiophosphate (ZDP). Auger emission spectroscopy was used to in situ monitor the changes in surface chemistry with rubbing under various loads. The metal disks examined included iron, titanium, rhodium, tungsten, molybdenum, and copper. For equivalent films of ZDP the film is a more effective lubricant for some metals than it is for others. The important active element in the compound varies with the metal lubricated and is a function of metal chemistry. The zinc in the ZDP is susceptible to electron beam induced desorption

The nature of surfaces and their influence in wear mechanisms

The wear of materials is strongly dependent upon the nature of the solid surfaces in contact, their properties and the nature of their films. Oxide films, orientation, crystal transformations, adhesive binding, crystal structure, hardness, and the presence of alloying agents are all shown to affect one or more of the forms of wear. The three most common forms of wear, adhesive, abrasive, and corrosive, are discussed in terms of the way each is affected by various material properties. Results presented indicate how wear can be optimized by concern for properties of materials

Effect of nature of oxygen interactions on friction of titanium, aluminum, and molybdenum

Friction studies were conducted with a gold pin contacting titanium, aluminum, and molybdenum surfaces after exposure to oxygen with various methods. Oxygen was adsorbed on the surface, it reacted with the surface, and the surface was ion bombarded with oxygen. The presence of oxygen was monitored with Auger spectroscopy. Titanium friction varied with the mode of the metal-oxygen interaction. It was highest with the adsorbed oxygen and least with ion bombardment using oxygen. Aluminum exhibited lower friction values for the reacted and the ion bombarded surfaces than for the surface having the adsorbed layer. With molybdenum the friction coefficients were generally the same despite the nature of the surface treatment with oxygen

Metal-dielectric interactions

Metal direlectric surface interactions and dielectric films on metal substrates were investigated. Since interfacial interaction depends so heavily on the nature of the surfaces, analytical surface tools such as Auger emission spectroscopy, X-ray photoelectron spectroscopy and field ion microscopy were used to assist in surface and interfacial characterization. The results indicate that with metals contacting certain glasses in the clean state interfacial, bonding produces fractures in the glasses while when a film such as water is present, fractures occur in the metal near the interface. Friction forces were used to measure the interfacial bond strengths. Studies with metals contacting polymers using field ion microscopy revealed that strong bonding forces could develop being between a metal and polymer surface with polymer transferring to the metal surface in various ways depending upon the forces applied to the surface in contact. With the deposition of refractory carbides, silicides and borides onto metal and alloy substrates the presence of oxides at the interface or active gases in the deposition plasma were shown to alter interfacial properties and chemistry. Auger ion depth profile analysis indicated the chemical composition at the interface and this could be related to the mechanical, friction, and wear behavior of the coating

Friction behavior of members of the platinum metals group with gold

The adhesion and friction behavior of the platinum metals group was examined with clean surfaces and surfaces selectively contaminated with oxygen, vinyl chloride (C2H3Cl), and methyl mercaptan (CH3SH). A pin or disk specimen configuration was used with the pin being a single crystal of gold of the (111) orientation and with the platinum metal disks also being single crystals of the (111) or (0001) orientation. Loads applied ranged from 1 to 10 g and a sliding velocity of 0.7 mm/min was employed. Results indicate adhesion and transfer of gold to all of the platinum metals. Despite this observation friction differences existed among the metals in the group. These differences are related to surface chemical activity. Adsorption of various friction reducing species was selective. With some adsorbates present strong adhesive forces between metals were still observed

The role of the micro environment on the tribological behavior of materials

The properties of the environment which exert an influence upon adhesion, friction, wear, and lubrication of materials in solid state contact are discussed. The effect of the environment upon lubricants and lubricant properties is considered in relation to the interaction of the lubricant with the material surfaces in solid state contact and the ability of lubricants to provide protective surface films

Application of surface analysis to solve problems of wear

Results are presented for the use of surface analytical tools including field ion microscopy, Auger emission spectroscopy analysis (AES), cylindrical mirror Auger analysis and X-ray photoelectron spectroscopy (XPS). Data from the field ion microscope reveal adhesive transfer (wear) at the atomic level with the formation of surface compounds not found in the bulk, and AES reveals that this transfer will occur even in the presence of surface oxides. Both AES and XPS reveal that in abrasive wear with silicon carbide and diamond contacting the transition metals, the surface and the abrasive undergo a chemical or structural change which effects wear. With silicon carbide, silicon volatilizes leaving behind a pseudo-graphitic surface and the surface of diamond is observed to graphitize

Effect of oxygen, methyl mercaptan, and methyl chloride on friction behavior of copper-iron contacts

Sliding friction experiments were conducted with an iron rider on a copper disk and a copper rider on an iron disk. The sputter cleaned iron and copper disk surfaces were saturated with oxygen, methyl mercaptan, and methyl chloride at atmospheric pressure. Auger emission spectroscopy was used to monitor the surfaces. Lower friction was obtained in all experiments with the copper rider sliding on the iron disk than when the couple was reversed. For both iron and copper disks, methyl mercaptan gave the best surface coverage and was most effective in reducing friction. For both iron and copper disks, methyl chloride was the least effective in reducing friction. With sliding, copper transferred to iron and iron to copper