Seiichiro Hironaka

Effects of oxygen on the load-carrying action of some additives

Abstract The mechanisms of the load-carrying action of sulfur and phosphorus additives were investigated in air and argon, using the hot wire method and a four-ball machine. Results in the former experiment showed that the sulfurization reaction between sulfur compounds and an iron surface was considerably retarded in air, owing to the formation of iron oxide. It was confirmed that the higher the reactivity of the additive the better was its tribological behavior in the standard testing procedure, regardless of the atmosphere. Elementary sulfur was superior to dibenzyl disulfide or diphenyl disulfide. Oxygen was as important an EP agent as sulfur compounds under partial EHD lubrication. The results are discussed in relation to some transitions in wear and friction behavior.

Friction and wear properties of graphite/glassy carbon composites

Abstract This paper describes the results of an experimental study of the friction and wear properties of graphite/glassy carbon (G/GC) composites. The frictional tests were performed in ambient air with a pin-on-disk friction apparatus. When the composition of graphite and glassy carbon was changed, the G/GC composite with 34 vol.% graphite content showed the lowest friction coefficient (μ≒0.13) and that with 24 vol.% graphite content showed the lowest specific wear amount (Ws≒2×10−7 mm3/Nm) at this test conditions. Compared with graphite and glassy carbon, G/GC composites showed lower friction coefficients and lower specific wear amounts. Consequently, G/GC composites are expected to be useful as self-lubricating materials.

Effects of some chemical factors on film failure under EP conditions

Abstract This paper is primarily concerned with the effects of sulfur- or phosphorus-type additives and of the atmosphere on EP lubrication failure as an extension of work reported previously. With a modified stepwise loading procedure, the effects of some EP additives on wear and friction were investigated using a four-ball machine. It was found, from the results of electron probe microanalysis, that the chemical nature of films on rubbing surfaces varied with the atmosphere and with the chemical structure of the sulfur compounds. The nature of the surface films correlated closely with the tribological behavior and may control the lubrication regimes. The less reactive additives had better frictional behavior in air because EHD effects can contribute to the concentrated contact. The transitions observed here are compared with those proposed by OECD-IRG ∗ . The method of evaluation of EP additives is discussed.

The effect of pentaerythritol partial ester on the wear of aluminum

Abstract The caprylic partial ester of pentaerythritol was synthesized and was used to lubricate an aluminum-steel system. The wear of this system under boundary conditions was investigated using a pin-on-disk apparatus. Penta erythritol partial ester, which contains both hydroxyl and ester groups, reacts with the surface aluminum atoms to form amorphous substances such as aluminum complexes or salts. These products act effectively as boundary lubricants for aluminum; this is confirmed by the relation between wear rate and load, microscope observation of the wear scars and wear particles and analyses of the wear particles by atomic absorption analysis, X-ray analysis and IR spectroscopy.

Effects of Adsorption of Some Surfactants on Antiwear Properties

The adsorption of organic polar compounds onto iron sulfide and onto iron oxide was investigated using a flow microcalorimeter. The effects of a combination of an iron sulfide surface and surfactants on wear were examined in air and argon atmospheres using a ball-on-dish friction machine. The polar interaction and reactivity between organic polar compounds and iron sulfide are important functions for wear reduction. This was shown from the results obtained in the measurement of the heat of adsorption, amount of adsorption, heat of desorption and iron content in the desorption solution. The adsorption of stearic acid on the steel ball sulfidized in H2S reduced wear significantly in the air atmosphere. Surfactants contribute considerably to wear reduction when used with sulfur EP additives which form an iron sulfide film.

Morphological study of the wear of crystalline polymers I: High density polyethylene

Abstract The morphology of the worn surface and wear debris of high density polyethylene (HDPE) slid against steel in air and water was studied. Electron micrographs and electron diffraction patterns of carbon replicas of the worn surfaces revealed that the molecular chains (crystallographic c axis) of HDPE were markedly oriented in the sliding direction. Annealing of the wear specimen caused lamellar crystals to form perpendicular to the sliding direction, suggesting folded-chain crystals linked by tie molecules and tie fibrils. Morphological consideration is also given to the wear mechanisms of HDPE in air and water.

Wear Behavior and Chemical Friction Modification in Binary-Additives System under Boundary-Lubrication Conditions

The present paper is primarily concerned with the synergistic effects of polar and organic sulfur compounds on the wear and surface roughness under boundary-lubrication (BL) conditions. The effects of lubricants containing the above two types of additives on the wear and the roughness of worn surface in a steel/steel sliding system have been investigated using a four-ball wear tester in air and argon atmospheres. In air, the combination of a fatty acid and a sulfur compound gives less wear and a smoother surface than would the sulfur compound alone in test run on worn surfaces. This surface smoothing is concerned with the friction modifications of surface caused by supplying binary additives and promoting elastohydrodynamic lubrication (EHL). In argon, on the contrary, it seems that the chemical reaction of sulfidized film with fatty acid causes the excessive wear. To control the evaporation of organic sulfur compounds and the effect of oxygen, a high-pressure-differential thermal analysis (HPDTA) was app...

Morphological study of the wear of crystalline polymers II: Isotactic poly(propylene)

Abstract The morphology of the worn surface and wear debris of isotactic poly(propylene) (PP) slid against steel in air and water was studied. From electron micrographs, electron diffraction patterns and X-ray diffraction patterns it was found that both the worn surface and the wear debris had a smectic structure. Plastic deformation of the surface of PP took place during frictional contact both in air and in water, giving rise to the formation of thick meandered fibrous aggregates with their longitudinal axes nearly perpendicular to the sliding direction and thin fibrils aligned parallel to the sliding direction.

Friction Properties of Fluorinated Compounds

The friction properties of synthetic fluorinated compounds such as n-C7F15-CH2OH, n-C7F15CH(OH)2, n-C7F15CH2NH2 and n-C7F15COOH, were investigated with a pendulum type friction tester in the steel/steel and steel/aluminum sliding friction systems. These fluorinated compounds gave different friction properties in the two systems. It is considered that this fact is due to the different chemical interaction of the fluorinated compounds with steel or aluminum surfaces.