Mating Ball Research Articles

S115014 トライボコーティングによる新しい表面改質技術の開発([S11501]トライボロジーの基礎と応用(1))

A novel surface modification technique named Brush Method, which combine traditional surface coating techniques and surface texturing techniques, is proposed. Tribological properties of treated SUJ2 disk specimens were investigated against 410 SUJ2 balls under the lubrication of poly-alpha-olefin (PAO) and PAO containing ZDDP (600 ppm of phosphorus) and MoDTC (700 ppm of molybdenum) called MoDTC+PZL-PAO. In both cases, a lower coefficient of friction and a higher abrasion of mating balls are obtained by Mo-tribo-coating films and micro scratches created by the brush treatment. Especially under the MoDTC PZL-PAO lubricant, a remarkable decrease of coefficient of friction was shown to decrease by 20%, while a remarkable increase of wear diameter of mating balls was shown, compared with untreated SUJ2 disk specimens.

Tribological properties of polymer composites with diamond-like carbon flakes

Composites of epoxy resin with diamond-like carbon (DLC) flakes were fabricated. The DLC flakes were prepared from a DLC film deposited by chemical vapor deposition on an aluminum substrate. The tribological properties of composites were evaluated in air and water environments using a reciprocating friction tester and an AISI 440C mating ball. The friction coefficient of the epoxy composite decreased from 0.90 to 0.69 in air and from 0.71 to 0.29 in water with the addition of DLC flakes. The specific wear rate of the composite also decreased from 5 × 10 − 5 to 7 × 10 − 6 mm 3/N m in air and from 4 × 10 − 5 to 4 × 10 − 6 mm 3/N m in water. In contrast, the wear of the mating ball increased. Furthermore, the tribological properties of DLC flakes as an additive in water were evaluated. The suspension of powdered DLC in water reduced the friction coefficient of epoxy resin against the AISI 440C mating ball. Furthermore, the wear of the resin was negligibly small, although severe abrasive wear on the mating ball was observed.

Tribological performance of surface engineered tool steel at elevated temperatures

Abstract Tribological components operating at elevated temperatures can experience high wear, oxidation, thermal fatigue and changes in mechanical properties. In this work, the friction and wear characteristics of plasma nitrided and surface coated (CrN and TiAlN) tool steel during sliding against AISI52100 bearing steel have been studied at room temperature and 400 °C respectively using a ball on disc machine. Surface profiler and SEM/EDS techniques were used to characterise the surface topography and resulting surface damage of the test specimens. The results show that the friction of plasma nitrided tool steel during sliding against bearing steel ball is very high at room temperature and it drastically drops at 400 °C. The wear is mainly abrasive at room temperature and adhesive at elevated temperatures. In case of CrN coated tool steel the friction is high but its wear is negligible at room temperature. At 400 °C, the friction decreases marginally and transfer of bearing steel to the coated CrN coated disc has been observed. The TiAlN coating has shown relatively lower friction, compared to CrN and negligible wear at room temperature. At 400 °C, the friction is very high and unstable and transfer of TiAlN coating to the mating ball occurs.

Transfer behavior in low-amplitude oscillating wear of nanocrystalline copper under oil lubrication

Nanocrystalline (NC) Cu samples were synthesized by means of surface mechanical attrition treatment, from which a layer of NC structure was formed on a coarse-grained Cu plate. Low-amplitude oscillating wear/fretting behaviors of the NC Cu samples were investigated under oil lubrication in comparison with those of as-annealed coarse-grained Cu samples. It was found the NC Cu possesses a markedly enhanced wear resistance and a higher friction coefficient relative to the coarse-grained Cu. A continuous metal transfer layer is formed on the mating ball after fretting against the NC Cu, while no material transfer occurs for the as-annealed Cu. The effects of experimental parameters and the hardness of Cu samples on the formation of a transfer layer have been systematically investigated. The transfer layer is evidenced to play an important role in the enhanced wear resistance of the NC Cu, but it has a trivial effect on its high friction coefficient.

Grain size effect on wear resistance of a nanostructured AISI52100 steel

We report that the sliding wear resistance of a nanostructured spheroidal pearlite steel varies with grain size: it increases when the grain size of the ferrite phase (Dα) increases from 8 to 32 nm, and decreases with a further increase in Dα. A maximum wear resistance at an average grain size of 32 nm, corresponding to the most significant material transfer on the mating ball, was analyzed in terms of the combination of hardness and plasticity.

Study on Tribological Performance of Fine-Grained Diamond Films

Friction and wear behavior of fine-grained diamond (FGD) films were investigated in the ambient air, deionized water and paraffin oil lubricating environment. The FGD films were deposited on WC substrates using HFCVD method and the tribologcial tests were conducted in a ball-on-plate type reciprocating friction tester where the mating balls were made of ball-bearing steel. Scanning electron microscopy (SEM), surface profilometer and Raman spectrascropy were used to study the characterizations of the deposited FGD films, and after sliding tests, the worn areas on both mating balls and FGD films were investigated and the wear debris layer adhered to the friction area of FGD films were analyzed with EDX. The experiment results suggested that FGD films exhibited steady friction coefficient as about 0.25 in water, lower than that in open air, which is up to 0.40; but the mating ball in water suffered much severer wear lost and its specific wear rate was more than two times higher than that in air, up to 3.6E-4 mm3N-1m-1. As while, a thick and compact layer of wear debris was observed on the worn area of FGD films sliding with water lubrication while only little debris existed in the diamond grain boundaries, which might dominate the friction process and attribute to the lower friction coefficient and higher specific wear rate in water environment. In oil environment, furthermore, both the friction coefficient and specific wear rate reached minimum value as low as 0.1 and 1.1E-4 mm3N-1m-1, no observable wear scar could be measured on the sliding surface of the FGD film.

Roughness effect of mating ball on friction of diamond-like carbon film and friction mechanism in water and air environment

The dependence of DLC film friction on the roughness of stainless steel mating balls was investigated in water and air environments. It was found that the steel ball surface parameters of Ra and surface density of summits (Dsum) showed a high correlation with the film friction in a water environment but in an air environment, the correlation was low with the friction coefficients scattered across the parameters of roughness. The difference in the frictional behaviors was explained by the presence of lubrication film that formed in the water environment. Furthermore, it was confirmed that the friction behaviour of DLC film in water environment was interpreted on the basis of boundary lubrication theory proposed by Nakahara.

Effect of Tempering on the Wear Characteristics of Induction-Hardened SPS5 Steel

In this study, the tempering effect on the wear characteristics of induction-hardened SPS5 steel was investigated. For this purpose, three tempering conditions were applied to control the hardness and microstructure of heat-treated SPS5 steel. Ball-on-disk wear tests have been performed using zircornia balls on the tempered specimens to determine the variation of wear characteristics. The results showed that friction coefficient decreased with increasing hardness for induction-hardened SPS5 steel. This seems to occur because real contact area between specimen and mating ball was affected by the specimen hardness. Also, we observe the wear type changes from the plowing wear to the adhesive wear as the hardness increases and the adhesive wear particles act as an obstacle to the transmission of the force of friction, reducing the coefficient of friction and the wear rate.

Friction and wear properties of NBR/PVC composites

AbstractAcrylonitrial butadiene rubber (NBR)/Polyvinyl chloride (PVC) composites with different PVC content were prepared. The effect of PVC content on the mechanical strength and tribological properties of the NBR/PVC composites was investigated. The morphologies of the worn traces and debris of NBR/PVC composites and worn traces of mating ball were observed using a scanning electron microscope (SEM). It was found that the friction and wear of NBR/PVC was lower than that of NBR without PVC. The NBR/PVC composite with 30% PVC content showed the best synthetic mechanical and tribological properties. The inferior elastic properties and the lesser deformation under the applied load of composites with PVC resulted in hysteric force and adhesion force decrease, which leading to a lower friction and wear of NBR/PVC composites. The frictional failure unit of NBR70/PVC30 composite being smaller should be an important reason of the wear of the composite being lowest. The lubricating effect of PVC played an important role in decreasing the friction coefficient and wear of NBR/PVC composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Tribochemical interactions of Si-doped DLC film against steel in sliding contact

This study concerns the effects of tribochemical interactions at the interface of Si-DLC (silicon-doped diamond-like carbon) film and steel ball in sliding contact on tribological properties of the film. The Si-DLC film was over-coated on pure DLC coating by radio frequency plasma-assisted chemical vapor deposition (r.f. PACVD) with different Si concentration. Friction tests against steel ball using a reciprocating type tribotester were performed in ambient environment. X-Ray photoelectron spectroscopy (XPS) and auger electron spectroscopy (AES) were used to study the chemical characteristics and elemental composition of the films and mating balls after tests. Results showed a darkgray film consisting of carbon, oxygen and silicon on the worn steel ball surface with different thickness. On the contrary, such film was not observed on the surface of the ball slid against pure DLC coating. The oxidation of Si-DLC surface and steel ball was also found at particular regions of contact area. This demonstrates that tribochemical interactions occurred at the contact area of Si-DLC and steel ball during sliding to form a tribofilm (so called transfer film) on the ball specimen. While the pure DLC coating exhibited high coefficient of friction (∼0.06), the Si-DLC film showed a significant lower coefficient of friction (∼0.022) with the presence of tribofilm on mating ball surface. However, the Si-DLC film possesses a very high wear rate in comparison with the pure DLC. It was found that the tribochemical interactions strongly affected tribological properties of the Si-DLC film in sliding against steel.

Formation of lubrication film of diamond-like carbon films in water and air environments against stainless steel and Cr-plated balls

Low-friction behaviour of diamond-like carbon (DLC) films in a water environment in regard to their lubrication films was investigated. Previously, these were reported to consist of Fe, Cr, C, and O, when formed against a stainless steel ball. As the role of Cr in lubrication film formation was not clear, a Cr-plated ball was used as a mating ball to investigate it in the present work. The friction coefficient of the DLC/Cr-plated ball system was lower compared with the DLC/steel one, in water and ambient environments. Furthermore, the frictional behaviour at the initial stage against the Cr-plated ball was quite stable comparing with that against the steel ball. However, in long time friction tests (7200 cycles) in water, the friction coefficient was similar for both sliding pairs. Therefore, it is considered that Cr on the surface of mating balls promotes the formation of a lubrication film in a water environment. Difference of the frictional behaviour in water and air is correlated with the formation of lubrication film.

Wear resistance of Fe–28Al–3Cr intermetallic alloy under wet conditions

Wear behaviour of iron aluminides (Fe–28Al–3Cr at.%) alloy has been investigated under wet conditions using ball on plate sliding wear tester. Wear resistance was examined against tungsten carbide (WC) ball sliding over the iron aluminide plate at room temperature. Wear tests were carried out at 3 N and 5 N load conditions at different sliding frequency of mating ball. The micromechanisms responsible for wear were identified to be microcutting, micropitting, and microcracking of deformed subsurface zones under wet conditions.

Low-friction behaviour of diamond-like carbon films in a water environment

Lubrication films of DLC coating were investigated using transmission electron microscope (TEM) analyses. The friction behaviour of DLC and Si-doped DLC films against AISI 440C stainless steel ball was evaluated under water using a ball-on-disk type reciprocating friction tester. The lubrication film at wear scar of mating ball was determined by cross-section TEM and EDS. Thin lubrication films (5–20 nm) on a flat area of wear scars were observed. Furthermore, it was confirmed that the lubrication film for Si-DLC had a double-layer structure and that of DLC had a monolayer structure. The localization of Cr was identified in lubrication films. It is concluded that the structure of the lubrication film played an important role in the low friction behaviour in a water environment.

DOES LARGE BODY SIZE IN MALES EVOLVE TO FACILITATE FORCIBLE INSEMINATION? A STUDY ON GARTER SNAKES

A trend for larger males to obtain a disproportionately high number of matings, as occurs in many animal populations, typically is attributed either to female choice or success in male-male rivalry; an alternative mechanism, that larger males are better able to coercively inseminate females, has received much less attention. For example, previous studies on garter snakes (Thamnophis sirtalis parietalis) at communal dens in Manitoba have shown that the mating benefit to larger body size in males is due to size-dependent advantages in male-male rivalry. However, this previous work ignored the possibility that larger males may obtain more matings because of male-female interactions. In staged trials within outdoor arenas, larger body size enhanced male mating success regardless of whether a rival male was present. The mechanism involved was coercion rather than female choice, because mating occurred most often (and soonest) in females that were least able to resist courtship-induced hypoxic stress. Males do physically displace rivals from optimal positions in the mating ball, and larger males are better able to resist such displacement. Nonetheless, larger body size enhances male mating success even in the absence of such male-male interactions. Thus, even in mating systems where males compete physically and where larger body size confers a significant advantage in male-male competition, the actual selective force for larger body size in males may relate to forcible insemination of unreceptive females. Experimental studies are needed to determine whether the same situation occurs in other organisms in which body-size advantages have been attributed to male-male rather than male-female interactions.

Friction and wear of carbon nanohorn-containing polyimide composites

Polyimide (PI)-based composites containing single-wall carbon nanohorn aggregate (NH) were fabricated using the spark plasma sintering (SPS) process. For comparison, composites with carbon nanotube (NT) and traditional graphite (Gr) were also fabricated. The NH was produced using CO2 laser vaporization and a graphite target and the NT was produced by a chemical synthesis method. We evaluated the friction and wear properties of the PI-based composites with a reciprocating friction tester in air using an AISI 304 mating ball. NH drastically decreased the wear of PI-based composites; the specific wear rate of composite with NH of only 5 wt% was of the order of 10−8 mm3/Nm, which was two orders of magnitude less than that of PI alone. The wear reduction ability of NT seemed to be slightly inferior to that of NH, although it was considerably better than that of Gr. NH and NT lowered the friction of composites. The friction coefficient of composite with 10 wt% NH was less than 0.25, although it was slightly higher than that of composite with 10 wt% Gr. There was no clear difference in the friction reduction effect of NH and NT. The further addition of Gr to composites with NH or NT rather deteriorated the antiwear property of composites, although the friction coefficient was slightly reduced. The transferred materials existed on the friction surface of the mating ball, sliding against composites with three types of carbon filler. These transferred materials seemed to correlate with the low friction and wear properties of composites.

The First Observation of Breeding of the Long-tailed Clawed Salamander, Onychodactylus fischeri, in the Field

Breeding of the long-tailed clawed salamander, Onychodactylus fischeri, was observed in the field for the first time. The breeding site was located within a brook in a cave. At the site, more males were observed than females. To inseminate a pair of egg sacs from each female, more than five males formed a mating ball. The oviposition site on the wall, whose upper margin was approximately 40 cm below the water surface, was 2 m wide and 1 m high. A total of 173 pairs of egg sacs were found at the site, of which most were attached to the side of rock walls in a brook.

Snakes in search of sex: the relation between mate-locating ability and mating success in male garter snakes

Is a male’s ability to find fertilizable females an important determinant of his mating success? We exploited unique logistical advantages offered by courting aggregations of garter snakes, Thamnophis sirtalis parietalis, in Manitoba, Canada, to ask: (1) does the order at which a male arrives at a solitary female affect either his courtship tactics or his chances of inseminating her; and (2) does a male’s body size affect his probability of arriving before his rivals? Experimental trials in the field and in outdoor arenas (to control group size and arrival intervals) suggested that, in the area near the main den, being the first to find a solitary female conveys limited or no fitness benefits to a male snake. Other males were likely to arrive before the male could achieve copulation; and early arrival did not guarantee optimal positioning within the mating ball. Thus, late-arriving males were as likely to obtain copulations as were early arrivers. Male body size enhanced mating success more in early arrivers than latecomers, but did not affect arrival times. However, although mate-finding ability was unimportant for male garter snakes competing near the den, it was critical in surrounding woodland where densities of rivals were much lower.

Friction behaviour of Si-DLC/DLC multi layer films on steel substrate in water environment

The tribological properties of diamond-like carbon (DLC) films over-coated by various thicknesses of Si-doped layers were investigated in a water environment. The multi-layer DLC films were deposited on a stainless steel substrate by pulsed-bias CVD technique. A dependence of friction coefficients on thickness of the over-coated layer was not observed and the friction coefficients of the films showed a stable and low value of approximately less than 0.1. On the other hand, specific wear rates of the films and mating balls depended on the thickness of the layers. Furthermore, the films with thin layers (less than 0.1 μm) and a thick layer (over 0.34 μm) showed the rupture on wear tracks. It was concluded that the optimized thickness of the layer (0.16 μm) improved the rupture strength of film, and showed a low specific wear rate of film and mating ball. It was found that the optimization of the thickness of the over-coated layer was important in achieving good tribological properties of Si-DLC/DLC multi-layer films.

Tribological characteristics of diamond-like carbon films based on hardness of mating materials

Tribological testing of DLC films was conducted using a rotating type ball on a disk friction tester in a dry chamber. This study made use of four kinds of mating balls that were made with stainless steel but subjected to diverse annealing conditions in order to achieve different levels of hardness. In all load conditions using martensite mating balls, the test results demonstrated that the friction coefficient was lower when the mating materials were harder. The high friction coefficient found in soft martensite balls appeared to be caused by the larger contact areas. Measuring the wear track of both the DLC films and the mating balls revealed a similar tendency compared to the results of friction coefficients. The wear track on the mating balls indicated that a certain amount of material transfer occurs from the DLC film to the mating ball during the high friction process. Raman spectra analysis showed that the transferred materials were a kind of graphite and that the contact surface of the DLC film seemed to undergo a phase transition from carbon to graphite during the high friction process.

Friction and Wear of Various DLC Films in Water and Air Environments

Three types of diamond-like carbon (DLC) films, pure DLC, F-containing DLC, and a Si-containing DLC film, were deposited on a WC–Co substrate by a plasma-enhanced CVD technique. Friction and wear properties were determined using a ball-on-plate type reciprocating friction tester in water, comparing the water results to those in ambient air. The friction coefficient of DLC and F–DLC films in water was considerably lower than that in air. With Si–DLC, the friction was almost the same level in both water and air, and was less than 0.1. The specific wear rate of films in water was much smaller than that in air and varied around the low level of 10−8 mm3/Nm in water, The mating ball wear was also less than 10−8 mm3/Nm. With DLC and F–DLC films, the transferred amount of material on the friction surface of a mating ball was larger in a water environment than that in air. With a Si–DLC film, the difference in the transferred amount when exposed to either the water or air environment was negligible.