E. E. Klaus

Tribochemical Mechanism of Alumina With Water

Water has been found to exhibit significant effects on the tribological behavior of alumina. A film-like substance was found on the surfaces of water lubricated alumina wear surfaces, suggesting the possibility of tribochemical reaction between water and alumina in the contact junction. This paper describes an investigation of the alumina/water tribosystem to determine the chemical interaction between these two materials under rubbing conditions. A combination of x-ray powder diffraction and thermogravimetric analysis (TGA) has been used to investigate the kinetics of alumina/water reactions. These experiments have determined that transition (gamma) alumina reacts with water to form hydroxides of aluminum. At high temperature (≊ 200°C) aluminum oxide hydroxide (boehmite—AlO(OH)) is formed, while at lower temperature (≊ 100°C) the formation of aluminum trihydroxide (bayerite—Al(OH)3) is favored. Aluminum trihydroxide (bayerite) was found in the wear debris from water lubricated wear tests. A mechanism for ...

A Thin-Film Test for Measurement of the Oxidation and Evaporation of Ester-Type Lubricants

A new thin-film oxidation test has hen developed for the quantitative evaluation of aircraft gas turbine (ester) lubricants. Problems associated with diffusion limitation are minimized by the use of a small sample (20-200 μL) with a relatively large fixed area of fluid-gas contact. Analysis with gel permeation chromatography (GPC) gives a semi-quantitative measurement of additive depletion, and measures the quantity of original fluid reacted and the quantities of oxidized products formed. By a careful calibration under a nitrogen atmosphere, the volatility loss is measured and calculated independently of the oxidation reaction. Test repeatability is excellent. The system is adaptable for a wide range of time-temperature studies and allows the duplication of system conditions in conditions in equipment, such as in the aircraft gas turbine lubrication system. A wide variety of catalytic surfaces typical of those found in structural and bearing portions of the lubrication system can be duplicated. The overal...

Viscosity-Pressure Correlation of Liquids

A single correlation was obtained to predict Newtonian viscosity-pressure coefficients of mineral oils, resin and polymer blends, pure hydrocarbons, and nonhydrocarbons. The correlation has been tested for a temperature range from 0°c (32 °F) to 135°C (275 °F). The empirical correlation makes use of atmospheric viscosity and density at the temperature of interest and viscosity-temperature property (mo) of the fluids. When the correlation was compared with other leading correlations, it was shown to require less physical-property data, apply to n wider range of chemical compositions, cover a wider range in fluidity, and provide greater accuracy. The correlation is presented in the form of a polynominal equation. Presented at the 34th Annual Meeting in St. Louis, Missouri, April 30-May 3, 1979

Lubrication from the Vapor Phase at High Temperatures

Vapor phase lubrication has been demonstrated using a conventional four-ball wear Lester run at 370°C using M50 hot hardness steel ball bearings. The four-ball wear tester was modified to control both the temperature and the environment surrounding the ball pot and spindle. The lubricant in all cases comprised a homogeneous gas phase mixture of nitrogen and phosphate ester vapors. The two phosphate esters used were tributyl phosphate (TBP) and tricresyl phosphate (TCP). The volume percent phosphate ester vapor in nitrogen ranged from 0.10 to 6.0 percent. The minimum temperature of the four balls was maintained at 370°C which was always at least 50°C higher than the temperature of the homogeneous vapors delivered so that there was no possibility of vapor condensation on the wear contacts. Vapor phase lubrication by phosphate esters appears to be as effective at a bulk temperature of 370°C as typical nonadditive mineral oils are in the liquid state at room temperature to 75°C. For example, TCP delivered fro...

A Study of Tricresyl Phosphate as an Additive for Boundary Lubrication

A method of combining thin-layer chromatography with activation analysis to measure quantitatively the individual impurities in tricresyl phosphate (TCP) is described. The relative amounts and types of impurities found in commercial grades of TCP are discussed. Preparative thin-layer chromatography and iron powder chromatography are applied to produce TCP samples with known concentrations of several impurities. The use of the four-ball wear tester as a method of determining trends in wear values as a function of base stock and additive quality is demonstrated. The relationship of acid phosphate rather than TCP concentration to antiwear properties of compounded lubricants is suggested by transition load studies. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference held in Chicago, Illinois, October 17–19, 1967.

Effect of Some Physical and Chemical Properties of Lubricants on Boundary Lubrication

A series of studies was conducted in the jour-ball wear tester to better define the roles of volatility, environment, and polar impurities in boundary lubrication. A number of well-defined, super-refined mineral oils, free from polar impurities, were utilized as base stocks for these studies. The effect of volatility as a factor in wear is conclusively shown. Volatile base stocks were used to illustrate the effects of less volatile polar and nonpolar impurities. The relative importance of volatility of lubricity additives is also demonstrated. Methods for the quantitative measurement of dissolved gases including oxygen in the lubricant under practical test conditions are illustrated. The relationship between dissolved oxygen and wear is shown for several lubricants. The interrelationship between dissolved oxygen, lest temperature, load, and fluid is also discussed. Presented as an American Society of Lubrication Engineers paper at the Lubrication Conference held in Rochester, New York, October 15–17, 1963.

Some Chemical Effects in Boundary Lubrication Part I: Base Oil-Metal Interaction

Base fluid-metal interactions of a super-refined paraffinic mineral oil were studied. Wear debris from a Shell Four-ball wear tester was analyzed. Based on the amount of iron distributed among used oil, organic solid, iron particles, and iron oxides, one is able to interpret the wear phenomenon in terms of mechanical and chemical processes. Oxygen concentration at the wear junction controls the type of the chemical interactions between the metal and the lubricant. These chemical reactions appear to be controlled by the thermal gradient at the junction; catalytic effects by the metal are insignificant. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Kansas City, Missouri, October 3–5, 1977

Estimation of the Molecular Junction Temperatures in Four-Ball Contacts by Chemical Reaction Rate Studies

A super-refined paraffinic mineral oil has been used to study the chemical reactions under boundary conditions in a four-ball wear tester. By quantatively analyzing the wear debris generated, chemical reaction rate data used to correlate between dynamic wear tests and static, externally controlled temperature runs. The reaction temperature at the wear junction has been estimated to be 351°C for 40kg load, 600 rpm, 75°C bulk oil temperature. This temperature is higher than the Blok-Archard flash temperatures calculated under the same conditions. Presented at the 32nd Annual Meeting in Montreal, Quebec, Canada, May 9–12, 1977

The Chemical Degradation of Ester Lubricants

Gel permeation chromatography is shown to be a valuable technique for analysis of the oxidation and thermal degradation products of various types of esters. Esters potentially useful as synthetic lubricant basestocks, such as tridecyl pelargonate (a mono-ester), di-2-ethylhexyl sebacate (a diester) and trimethylolpropane triheptanoate (a neopentyl polyolester) form products of up to 50 000 molecular weight when oxidized at high temperatures. The oxidation products have been separated by molecular weight using preparative gel permeation chromatography (GPC) and then have been analyzed spectrographically. The polymeric products of oxidation show similar chemical bond structure for the various types of esters studied. The importance of oxygen and metal catalysis on product formation is demonstrated. The influence of steel surfaces on the products of oxidation suggests a tribochemical reaction resulting in the ultimate formation of a “friction polymer.” Presented at the 33rd Annual Meeting in Dearborn, Michig...

A mechano-chemical descriptive model for wear under mixed lubrication conditions

Abstract The processes of lubrication are systematically analyzed and explained with the aid of recent experimental discoveries. Effective lubrication often involves surface chemical reactions which are dependent on contact geometry, load, speed, and environmental influences. Materials properties such as hardness, elasticity, and others also affect the wear outcome. Fluid mechanics under the influence of interfacial pressures and temperatures control a significant portion of the wearing processes. A conceptual model is proposed to link all these factors in a “lines of defense” framework and to discuss how wear can be predicted based on a probabilistic model. The model proposes a series of criteria for various combinations of chemically controlled and materials properties controlled situations.