Faculty Profiles - UMEHARA, Noritsugu

Effect of Mating Material and Graphitization on Wear of a-C:H Coating in Boundary Base Oil Lubrication Reviewed International journal

Kouami Auxence Melardot Aboua, Noritsugu Umehara, Hiroyuki Kousaka, Takayuki Tokoroyama, Motoyuki Murashima, Mohd Muhyiddin Bin Mustafa, Yutaka Mabuchi, Tsuyoshi Higuchi, Masahiro Kawaguchi

Tribology Letters Vol. 68 ( 1 ) page： 24 2020.1

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

Hydrogenated amorphous carbon (a-C:H) coating exhibits different wear behaviors depending on its counterpart material in boundary lubricated sliding contact. In previous works, tribological behaviors of a-C:H coating were investigated against steel, chromium, and germanium counterpart materials. The specific wear rate of a-C:H coating was found to decrease with the ability of its counterpart material to react with or dissolve carbon. The present study investigated how graphitization of a-C:H coating's top layers and interactions of the counterpart material with carbon influence wear behaviors of a-C:H coating in boundary lubrication. Results show that a-C:H coating shows graphitization of its top layers regardless the counterpart material. Correlation with differences in wear behaviors of the a-C:H coating leads to the conclusion that graphitization will induce high wear of a-C:H coating only when there are also atomic interactions between the DLC coating and its counterpart material.

DOI： 10.1007/s11249-019-1248-6

The tribological property of DLC under lubrication with GDOP and GDTP additives having glycerin and phosphate structure

EFFECTS OF LUBRICATION CONDITION ON FRICTION AND WEAR IN OIL LUBRICATION FOR ALUMINIUM ALLOY BEARINGS WITH VARIOUS CARBONACEOUS HARD COATINGS

Umehara Noritsugu, Kitamura Tomoki, Tokoroyama Takayuki, Murashima Motoyuki

7TH INTERNATIONAL CONFERENCE INTEGRITY-RELIABILITY-FAILURE (IRF2020) page： 1045 - 1046 2020

KANI Takumi, TOKOROYAMA Takayuki, UMEHARA Noritsugu, MURASHIMA Motoyuki, YAGISHITA Kazuhiro

The Proceedings of Mechanical Engineering Congress, Japan Vol. 2020 ( 0 ) page： S11311 2020

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

In general, several mechanical parts are subjected to friction and wear. To prevent unfavorable wear and high friction coefficient, additives can work to reduce friction force, to build up thin film on the surfaces which is so-called tribofilm. Recently, Diamond-Like Carbon (DLC) is focused because it has excellent low friction and high wear proof as solid lubricant. However, several researchers already reported that ta-C showed abnormal wear when it rubbed with GMO that is a kind of additive, although it showed very low friction coefficient. To improve friction property, GDTP and GDOP was developed that has structure of GMO and dithio-phosphate functional group derived from ZnDTP which has high wear resistance. To clarify the effects of GDOP, we performed XPS analysis after the friction tests. In the friction tests, an a-C:H coating, and SUJ2 balls were used under boundary lubrication condition at 20, 50 and 80 ℃, and applying normal load was 1 N. Friction tests were conducted in PAO (Poly-α-olefin) oil, PAO with each GMO, GDTP and GDOP additives. In PAO with GDOP situation, the friction coefficient decreased down to 0.05. And the specific wear rate of SUJ2 ball was larger than with GMO and GDTP. The result of XPS analysis, although the binding energy of PO4 was observed, that of FePO4 was hardly observed. This suggests that when GDOP was added, the tribofilm that increased friction coefficient was not formed because PO4 and Fe hardly reacted. As a result, the wear of an SUJ2 ball was small volume.

DOI： 10.1299/jsmemecj.2020.s11311

"FRICTIONLESS" DIAMOND-LIKE COATINGS AND IN-SITU OBSERVATION USING REFLECTANCE SPECTROSCOPY

Umehara, N

7TH INTERNATIONAL CONFERENCE INTEGRITY-RELIABILITY-FAILURE (IRF2020) page： 7 - 8 2020

The Surface Enhanced Raman Scattering Analysis for Carbonaceous Coating by Using Au Nano-Particles Reviewed

Tokoroyama Takayuki, Murashima Motoyuki, Umehara Noritsugu

Tribology Online Vol. 15 ( 5 ) page： 300 - 308 2020

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Society of Tribologists

In general, Raman analysis is one of the useful candidates to obtain structure of carbonaceous coatings. To improve the depth resolution of Raman analysis, surface-enhanced Raman Scattering (SERS) using gold nanoparticles (Au nanoparticles: AuNPs) and Au sputtered particles were investigated. The analysis was conducted to approximately 1.7, 2.4, 4.7, and 10.0 nm thickness of carbon coatings on silicon substrate with a 532 nm incident wavelength laser. The results indicated that the underlying silicon substrate was detected in the results of the Au sputtering method. Contrastingly, the underlying silicon substrate was not detected by the AuNPs method. This result clarified that using the AuNPs method, the detection depth of the carbon film was approximately 1.7 nm or less. The a-C:H coating was processed using a calotester, and SERS measurements at different depths were performed for the 633 and 532 nm wavelengths using the AuNPs method. As a result, the IG peak position tended to increase from the vicinity of the inter face between the a-C:H coating and the substrate to the surface. In addition, the ID/IG ratio was as low as 0.28 near the substrate and 0.72 at 3800 nm.

DOI： 10.2474/trol.15.300

Effect of doped tantalum in ta-CNx film or tantalum as counterpart material on the friction and wear properties of ta-CNx Reviewed

HOJO Koki, UMEHARA Noritsugu, TOKOROYAMA Takayuki, MURASHIMA Motoyuki

Transactions of the JSME (in Japanese) Vol. 86 ( 888 ) page： 20-00018 - 20-00018 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Mechanical Engineers

In order to clarify the effect of Ta (tantalum) content on the friction and wear characteristics of the ta-CNx (tetrahedral amorphous carbon nitride) coating, an IBA-FAD (Ion Beam Assisted Filtered Arc Deposition method) was applied to generate hard carbonaceous coating to achieve low friction coefficient in ambient air. Following research works clarified that Ta containing carbon nitride (CNx:Ta) showed friction coefficient lower than 0.05 in ambient air, however, the coating only had around 10 GPa hardness which was assumed to be soft in industrial fields. To confirm Ta containing to the ta-CNx coating on friction and wear properties, ta-CNx:Ta coating was synthesized by IBA-FAD and an arc plasma gun which supplied different amount of Ta by using pulse discharge technique (100 or 200 pulse/min.). The hardness of ta-CNx was approximately 54 GPa, then the hardness of Ta containing ta-CNx became softer than ta-CNx such as approximately 33 GPa (ta-CNx:Ta200). After the ball-on-disk friction test between those coatings and SUJ2 disk, a specific wear rate of those coatings did not along with its hardness. From the XPS (x-ray photoelectron spectroscopy) analysis, oxygen/carbon ratio of the topmost coating surface decreased by containing Ta. Those results implied that Ta in the coating may have a possibility to prevent oxidation of carbonaceous coating. The friction coefficient of ta-CNx, ta-CNx:Ta100 and ta-CNx:Ta200 showed around 0.15 during friction test. To confirm the importance of Ta transformed layer on low friction property, friction test between ta-CNx coating and thin Ta coated SUJ2 disk was conducted. The friction coefficient of the pair became the lowest among them which value was approximately 0.08.

DOI： 10.1299/transjsme.20-00018

Preventing coagulated-blood adhesion on a coated electrosurgical knife Reviewed

TOKOROYAMA Takayuki, KOBAYASHI Masahiro, MURASHIMA Motoyuki, UMEHARA Noritsugu, OGAWA Koki, YOROZU Takayuki, UCHIDA Junichi

Transactions of the JSME (in Japanese) Vol. 86 ( 889 ) page： 20-00273 - 20-00273 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Mechanical Engineers

In the past several decades, electro medical equipment has been developing to enhance surgical technologies. Using electro surgical knife is very common in everywhere of medical scene now a days. An electro surgical knife is consisted with power supply, metal tip and return electrode. In the case of using it to stop bleeding by coagulation mode, the tip surface is frequently covered by coagulated blood, then it is not able to discharge again. It means that the surgeons should replace it to new metal tip to continue surgical operation. In order to overcome this problem, some tips are covered by silicon type coating to prevent coagulated blood adhesion. However, it still has problems of continuous using, low heat invasiveness for human organs and how design such tip surface. In this study, three different type coating tips and a non-coated tip were prepared to compare temperature rising abilities and coagulated blood adhesion on the surface. As a result, fully surface coated types and blade’s edge uncovered type realized excellent prevention ability of blood coagulation adhesion onto surface. Especially for the side edge uncovered type, it exhibited low temperature rising ability after the temperature exceeded 100 degree C. This result indicated that side edge uncovered type is one of the suitable design to prevent exceed temperature rising.

DOI： 10.1299/transjsme.20-00273

In –situ analysis of two phase lubricant oil film with a reflectance spectroscopy Reviewed

YAMADA Takazumi, UMEHARA Noritsugu, TOKOROYAMA Takayuki, MURASHIMA Motoyuki, SATO Taku, OHARA Kenji, HANYUDA Kiyoshi

Transactions of the JSME (in Japanese) Vol. 86 ( 884 ) page： 19-00315 - 19-00315 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Mechanical Engineers

Two phase lubricant has attracted attention as a lubricating oil with little change in viscosity with temperature change. The two phase lubricant consist of the low and high viscosity base oils which are miscible at high temperature but not at lower temperature. For exmaple, Mineral or synthetic base oil are used as a low viscosity lubricant and PAG（polyalkylene glycol）. In the high temperature region, PAG dissolves into mineral or synthetic base oil and the viscosity reduction is relieved. However, the structure and frictional characteristics of the oil film at the sliding part have not been elucidated. In this paper, in-situ analysis of the oil film formed on the friction surface was carried out with a reflection spectroscopic film thickness meter. And, this paper clarified the influence of the oil film structure and oil film thickness of the two phase lubricant and its friction characteristics. As a result, it was suggested that the oil film of the two phase lubricant in the sliding part was a multilayer due to the adsorption layer of PAG. In addition the two phase lubricant showed a friction coefficient lower by about 0.03 to 0.07 at the experimental temperature compared to PAO, and it was clarified that a thick oil film was formed.

DOI： 10.1299/transjsme.19-00315

The micro-meter-sized plastic asperities by AC electric field for Poly-vinyl chloride solvent Reviewed

YAMADA Yusei, TOKOROYAMA Takayuki, MURASHIMA Motoyuki, UMEHARA Noritsugu

Transactions of the JSME (in Japanese) Vol. 86 ( 892 ) page： 20-00228 - 20-00228 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Mechanical Engineers

In order to create an inexpensive micrometer-sized plastic asperities, a polyvinyl chloride solvent dissolved in acetone was prepared so that the solvent droplet was put on silicon substrate and placed between parallel plate electrodes (the gap was 5 mm). The effects of concentration, DC/AC and their combination voltage on the creation of micrometer-sized plastic asperities were clarified. As a result, asperities with a height of more than 10 μm were observed from a solvent concentration more than 2.51 mg/ml. It was found that the asperities height increased linearly from around 10 μm to 14 μm with the applied voltage of 0.1 kV to 2.0 kV between the parallel plate electrodes. The effect of DC or AC of 2.0 kV on asperities height and number per unit area were conducted, then the height of asperities decreased from 14 μm to 10 μm when frequency was applied to 11 Hz. To confirm the effect of applying AC voltage on motion of the solvent droplet, high-speed camera observation was carried out. It was revealed that the droplet oscillated by applied AC voltage between parallel plates. The dimensionless height of the droplet increased and reached a maximum at AC 11 Hz. Finally, to clarify the effect of the initial voltage application method on the formation of asperities, a voltage was applied between the parallel plate electrodes under the conditions of DC/AC and no voltage for an initial evaporation time of 3 min. By applying AC 11 Hz during solvent evaporation period, it was clarified that the asperities dispersed most on the surface, then variations in asperities height were reduced.

DOI： 10.1299/transjsme.20-00228

The development of nano-sized PM filtration for a diesel engine oil using coagulation by an alternating electric field Reviewed

TOKOROYAMA Takayuki, SHIBASAWA Hotaka, UMEHARA Noritsugu

Transactions of the JSME (in Japanese) Vol. 86 ( 884 ) page： 20-00016 - 20-00016 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Mechanical Engineers

In general, a diesel engine does not have ignition system and it can ignite by self-ignition. It has pros that engine manufactures can consist engine components less than normal gasoline engines. However, diesel engines emit more particle matter (PM) rather than normal gasoline engine, so that diesel engines should have diesel particulate filter (DPF) to accumulate them even if it is in not only a exhaust gas but also an engine oil region. In this study, the authors clarified the possibility of PM accumulation method by using an alternating electric field applying between a metal needle and a plate to coagulate them as large particles more than 0.8 μm. The important parameters were an electric field intensity, frequency and applying time. The FESEM observation results indicated that approximately 100 nm-sized particles coagulated to be a large particle. Then, EDS analysis revealed that the particle did not include conventional engine additives such as zinc, molybdenum and calcium. Those results clearly indicated that the alternative electric field method can accumulate nano-sized PM.

DOI： 10.1299/transjsme.20-00016

Intelligent tribological surfaces: from concept to realization using additive manufacturing Reviewed International journal

M. Murashima, S. Yoshino, M. Kawaguchi, N. Umehara

Int J Mech Mater Des Vol. 15 ( 4 ) page： 757 - 766 2019.12

Investigating running-in behavior to understand wear behavior of ta-C coating with filtered cathodic vacuum arc deposition Reviewed International coauthorship International journal

Woo-Young Lee, Takayuki Tokoroyama, Motoyuki Murashima, Noritsugu Umehara

JURNAL TRIBOLOGI Vol. 23 page： 38 - 47 2019.12

Language：English Publishing type：Research paper (scientific journal) Publisher：MALAYSIAN TRIBOLOGY SOC-MYTRIBOS

In this study, to clarify running-in cycle and role of carbon transfer layer on wear, ta-C coatings were subjected to friction tests under 200 degrees C in air with a different sliding cycles. The steady state friction coefficient of 0.02 was obtained after finishing a running-in cycles approximately 2,000 cycles. During the steady state, wear rate of ta-C decreased with increasing number of cycles. Such the decrease of wear rate was explained by polished defects presented on surface and form carbon transfer layer on the counter-part material. The mechanism of those tribological properties was analyzed by Raman spectroscopy, scanning electron microscope observation and 3D measuring laser microscope.

Effect of Carbon Diffusion on Friction and Wear Behaviors of Diamond-Like Carbon Coating Against Germanium in Boundary Base Oil Lubrication Reviewed International coauthorship International journal

Kouami Auxence Melardot Aboua, Noritsugu Umehara, Hiroyuki Kousaka, Takayuki Tokoroyama, Motoyuki Murashima, Yutaka Mabuchi, Tsuyoshi Higuchi, Masahiro Kawaguchi

Tribology Letters Vol. 67 ( 2 ) page： 65 2019.6

Language：English Publishing type：Research paper (scientific journal)

Diamond-like carbon (DLC) coatings are designed to work under severe lubrication conditions. Depending on working environment, lubrication condition, and counterpart material, DLC coatings can exhibit crucial variations in their tribological behaviors. In the search of a counterpart material to improve tribological performances of DLC coatings in desired environment, we found out in previous work that carbon diffusion is an important parameter that influences the tribological behaviors of amorphous hydrogenated (a-C:H) coating in boundary lubrication. a-C:H coating exhibits high wear against steel counterpart material that has a high carbon affinity/solubility, while its exhibits lower wear against chromium counterpart material that has lower carbon affinity/solubility than steel. These recent findings imply that consideration of the carbon affinity/solubility when choosing a counterpart material for a-C:H coating in boundary lubrication might be of significant importance to improve tribological performances of a-C:H coating. This research investigates tribological behaviors of a-C:H coating against germanium counterpart material that has extremely low carbon affinity/solubility. Results show that there is no atomic interaction between a-C:H coating and germanium during friction and wear test, followed with a very low wear of a-C:H coating.

DOI： 10.1007/s11249-019-1179-2

The tribological potential of graphene growth from solid waste Reviewed International coauthorship

Noor Ayuma Mat Tahir, Fakulti Kejuruteraan Mekanikal, Mohd Fadzli Bin Abdollah*, Noreffendy Tamaldin, Hilmi Amiruddin, Mohd Rody Bin Mohamad Zin, Takayuki Tokoroyama and Noritsugu Umehara

Progress in Industrial Ecology – An International Journal Vol. 13 ( 4 ) page： 401 - 413 2019.4

Effect of oxygen on degradation of defects on ta-C coatings deposited by filtered arc deposition Reviewed International journal

Murashima Motoyuki, Deng Xingrui, Izuoka Hiroto, Umehara Noritsugu, Kousaka Hiroyuki

SURFACE & COATINGS TECHNOLOGY Vol. 362 page： 200 - 207 2019.3

Tribological properties of ta-CNx coating sliding against steel and sapphire in unlubricated condition Reviewed International journal

Xiaoxu Liu, Noritsugu Umehara, Takayuki Tokoroyama, Motoyuki Murashima

TRIBOLOGY INTERNATIONAL Vol. 131 page： 102 - 111 2019.3

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Tribo-behavior of tetrahedral amorphous carbon nitride (ta-CNx) coating in unlubricated condition was investigated in this study. Sliding against steel, low nitrogen content ta-CNx exhibits much lower friction and wear as temperature increases, with less adhesion wear than ta-C and remained relatively higher hardness (45.01 GPa). Nevertheless, against sapphire ta-C outperforms ta-CNx greatly, and graphitization could be found at 120 degrees C. With atmosphere humidity increasing, ta-CNx shows significantly decreased friction, implying the tribo-character of high sp(3) bonding structure. Meanwhile, dry air seems to be the harshest condition for ta-CNx, since O-2 in the atmosphere might lead to oxidized wear of ta-CNx even under room temperature. Furthermore, in humid N-2, as an inert gas with high humidity, ta-CNx shows the lowest friction and wear.

DOI： 10.1016/j.triboint.2018.10.022

Processing thin (<10 µm), dense, flexible α-Al2O3 films from nanopowders Reviewed International coauthorship International journal

TAKEUCHI Makoto, NIEDERMAIER Matthias, JANSOHN Monika, UMEHARA Noritsugu, LAINE Richard M.

Journal of the Ceramic Society of Japan Vol. 127 ( 2 ) page： 81 - 89 2019.2

Language：English Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan

Normally, it is very difficult to process thin ceramic films (<10 µm) except by vapor deposition methods. This is because in traditional ceramics processing, initial powder particle sizes (typical average particle sizes, APSs >200 nm) make it difficult to realize mechanically robust thin films after sintering to full density due to excessive grain growth. One solution to this problem is to start with nanopowders (APSs <100 nm). Here we present efforts to use simple, easily available nano δ-Al2O3 (transition or t-Al2O3) nanopowders (NPs) to process the subject films. Thus t-Al2O3 NPs when properly dispersed, doped with 0.5–5 wt.% MgO and ball milled with a polymeric binder provide castable systems. Wire wound roller drawing/tape casting provides access to thin green films (10–30 µm) with ≈75 wt.% ceramic loadings. Following binder burnout and careful sintering to temperatures of up to 1500°C/7 h/air but preferably slightly lesser conditions leads to dense ≤10 µm films with average α-Al2O3 grain sizes of 500–800 nm. At higher MgO concentrations, spinel phase separates during sintering likely inhibiting grain growth. These relatively dense films are flexible and translucent. Such films, because of their flexibility, may offer utility as catalyst supports, electronic substrates or as hard facings for other materials.

DOI： 10.2109/jcersj2.18099

The clarification of low friction mechanism in base oil lubrication of ta-CNx coating by in-situ observation with reflectance spectroscopy Reviewed

OKAMOTO Tatsuya, UMEHARA Noritsugu, TOKOROYAMA Takayuki, MURASHIMA Motoyuki

Transactions of the JSME (in Japanese) Vol. 85 ( 875 ) page： 19-00071 - 19-00071 2019

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Mechanical Engineers

Among DLC (Diamond-Like Carbon), ta-C (tetrahedral amorphous Carbon) coatings have been applied to improve fuel efficiency in automobile engines. Furthermore, it has been reported that a ta-CNx (tetrahedral amorphous Carbon Nitride) coating showed more than 50% lower friction coefficient in base oil lubrication compared to ta-C coating. On the other hand, the low friction mechanism of the ta-CNx coating has not been clarified. From the previous research, low friction mechanism of the ta-CNx coating in oil lubrication is considered that the increment of oil film thickness in accordance with increasing the oiliness of the transformed layer is important. However, the effects of oil film thickness and oiliness of the transformed layer on friction coefficient have not been quantitatively clarified, because oil film thickness and oiliness of the transformed layer have not been measured during friction. Therefore, in this research, the objective was set to clarify the low friction mechanism of the ta-CNx coating in oil lubrication by in-situ observation with reflectance spectroscopy, and oil film thickness and physical properties (polarizability, chemical bonding fraction) of the transformed layer was measured by in-situ observation with reflectance spectroscopy. Using in-situ observation with reflectance spectroscopy, film thickness, refractive index n and extinction coefficient k can be measured during friction test. And polarizability and chemical bonding fraction of the transformed layer were estimated from refractive index and extinction coefficient. From in-situ observation with reflectance spectroscopy, low friction mechanism of the ta-CNx coating in oil lubrication was proposed as shown below. The transformed layer was formed during friction and the polarizability of the transformed layer increased in accordance with decreasing C-Csp2 bonding fraction of the transformed layer, and PAO4 oil molecules were physically adsorbed on the transformed layer. As a result, oil film thickness increased and low friction occurred.

DOI： 10.1299/transjsme.19-00071

Effect of Pillar and Mesh Structure of Tetrahedral Amorphous Carbon (ta-C) Coatings on the Wear Properties and Fracture Toughness of the Coating Reviewed International coauthorship International journal

Bin Mustafa Mohd Muhyiddin, Umehara Noritsugu, Tokoroyama Takayuki, Murashima Motoyuki, Shibata Akinori, Utsumi Yoshiharu, Moriguchi Hideki

Tribology Online Vol. 14 ( 5 ) page： 388 - 397 2019

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Society of Tribologists

Wear by fracture is among the factors associated with the DLC coating failures in the tribological application. The current study investigated the link between the wear and the fracture-toughness on the novel Pillar and Mesh structure ta-C coatings, in addition to conventional ta-C coatings. The tribological properties of these coatings were examined under base-oil lubrication via ball-on-disk tribo-tester and micro indentation technique was used to characterize the fracture toughness. The wear track and the indentation mark were analyzed using the optical microscope, 3D laser microscope and FE-SEM. The friction coefficient for ta-C, Pillar ta-C and Mesh ta-C are within the range of 0.071 to 0.106. Mesh ta-C indicated the highest wear resistance, followed by the Pillar ta-C and conventional ta-C. Also, Mesh ta-C demonstrated the highest fracture-toughness value with 16.6 MPa·m1/2, followed by Pillar ta-C with 13.4 MPa·m1/2 in contrast to ta-C. Greater resistance to wear for ta-C with Pillar and Mesh structure was detected with an increased fracture-toughness and improvement in crack propagation inhibition. Moreover, the Pillar and Mesh ta-C provides superior rate of crack-energy dissipation as compared to the ta-C.

DOI： 10.2474/trol.14.388