Faculty Profiles - UMEHARA, Noritsugu

Papers - UMEHARA, Noritsugu

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Counterpart-dependent friction and wear of hydrogenated tetrahedral amorphous carbon under ultra-high vacuum Reviewed International coauthorship

Jae-Il Kim , Ji-Woong Jang, Noritsugu Umehara, Young-Jun Jang

Carbon Vol. 238 page： 120223 2025.4

Development of precipitation lubrication with palmitic acid and its friction mechanism Reviewed

Hashizume, N; Takano, R; Umehara, N; Tokoroyama, T; Zhang, RX; Hanyuda, K; Otsuka, A; Ueda, M

TRIBOLOGY INTERNATIONAL Vol. 200 2024.12

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

Conventional friction modifier MoDTC becomes ineffective at lower temperatures. This paper investigates the concept of “precipitation lubrication,” where saturated fatty acid precipitation enhances load-bearing capacity and solid lubrication at contact points to overcome this issue. PAO8 with 4.2 % palmitic acid lubricant was prepared, precipitating below 35 °C, reducing friction by approximately 14 % at 30 °C for both boundary and mixed lubrication. In situ reflectance spectroscopy demonstrated palmitic acid forming a solid layer on the disk specimen, preventing direct contact between asperities and significantly reducing friction. These findings underscore the effectiveness of palmitic acid precipitation in enhancing lubrication performance at lower temperatures.

DOI： 10.1016/j.triboint.2024.110066

Web of Science

Scopus

Effect of Water on Wear of DLC Coatings in High Temperature and Pressurized Ethanol Reviewed

Tokoroyama, T; Horikawa, S; Mimata, J; Umehara, N; Murashima, M

TRIBOLOGY LETTERS Vol. 72 ( 4 ) 2024.12

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

The friction and wear characteristics of a-C:H:Si and a-C:H coatings in an ethanol environment at 120 °C and 10 MPa focusing on the effects of water and dissolved oxygen in ethanol were investigated. The friction tests were conducted using an autoclave chamber, with gases (oxygen or nitrogen) and ethanol–water mixtures (0 and 6 vol.%). The wear acceleration of a-C:H:Si took place when it slid in ethanol with 6 vol.% water and pressurized by oxygen, thus the specific wear rate was the highest, approximately 1.8 × 10−7 mm3/Nm. The reason of this wear acceleration was assumed the effect of hardness reduction due to oxidation of the a-C:H:Si, so the O/C ratio by AES and the hardness of topmost surface by AFM nano-scratch were investigated. As a result, the higher O/C ratio showed higher specific wear rate due to the hardness reduction from 13.3 to 6.0 GPa. These findings highlight the role of water and dissolved oxygen in accelerating wear of a-C:H:Si coatings. Graphical abstract: (Figure presented.)

DOI： 10.1007/s11249-024-01910-z

Web of Science

Scopus

Proposal of a model for the influence of coating area on the electric field at the tip of electrocautery for suppressing tip charring and surgical smoke generation due to blood heating Reviewed

Journal of Advanced Mechanical Design, Systems, and Manufacturing Vol. 18 ( 6 ) page： AMDSM00210 2024.11

Corrosion and tribological properties of ta-C/ta-C: Ta coatings: Analysis of the influence of Ta-O/Ta-C ratio Reviewed

Li, LL; Tokoroyama, T; Zhang, RX; Umehara, N

Vol. 198 2024.10

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

Multilayer ta-C/ta-C: Ta coatings with varying total thicknesses (300, 600, and 1000 nm) and layer thickness ratios (1:0.5, 1:1, and 1:2) between the ta-C layer and ta-C: Ta layer were prepared. The study investigated the static corrosion resistance and tribological properties of the coatings in the NaCl solution. The static corrosion resistance positive correlation depended on the coating surface's Ta-O/Ta-C ratio. The lowest friction coefficient of 0.05 was obtained from the coating with a total thickness of 1000 nm due to the formation of the graphitized transfer film on the counterpart surface. A decreased sp2/sp3 ratio and the formation of tantalum oxide on the wear scar contributed to the lowest corrosion current, corrosive defect density, and wear rate.

DOI： 10.1016/j.triboint.2024.109916

Web of Science

Scopus

The development of B/Cr co-doped DLC coating by FCVA deposition system and its tribological properties at 300 °C Reviewed International coauthorship International journal

Zhang, RX; Lee, WY; Umehara, N; Tokoroyama, T; Murashima, M; Takimoto, Y

SURFACE & COATINGS TECHNOLOGY Vol. 487 2024.7

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Surface and Coatings Technology

The diamond-like carbon (DLC) coating prepared using filtered cathodic arc deposition (FCVA) lost its promising wear resistance under high temperatures. Element-doped DLC coatings have been investigated to suppress carbon oxidation reaction and subsequently enhance the wear resistance in high-temperature environments. Previous research clarified the excellent tribological properties of boron-doped DLC (B-DLC) but identified challenge such as arc discharge extinguishment and coating declamation (under high-temperature friction test). In this study, the introduction of Argon gas (10 sccm) during the deposition process stabilized stable arc discharge, resulting in high hardness and deposition rate. Moreover, a chromium interlayer and varying concentration of Cr dopant (0.5 %, 1.0 %, 3.0 % at.) were added to B-DLC to develop a stable, co-doped DLC with low friction and high wear resistance. Raman spectroscopy and nano-indentation revealed an increase in the disordered carbon structure and reduction in hardness and Young's Modulus with Cr doping. Macroscopic ball-on-disk friction test, showed 1 % Cr-doped B-DLC (a-C:B:Cr1) coating exhibited super low friction (avg. coefficient 0.02) and a low specific wear rate (<5.0 × 10−6 mm3/Nm). Raman spectroscopy indicated that the transferred graphite-like tribo-film onto the surface of Si3N4 counterparts contributed to stable low friction. Additionally, XPS analysis on the DLC coatings' wear track suggested the rich B–B bond might contribute to its high wear resistance. This successful improvement on element-doped DLC prepared by FCVA provided valuable insights for further exploration of DLC coating applied to various working situations.

DOI： 10.1016/j.surfcoat.2024.130968

Web of Science

Scopus

Evaluating Palm Oil Ester Base Oils as Eco-Friendly Alternatives in Lubricant Formulation Reviewed International coauthorship

Samihah Mustaffha, Darius El Pebrian, Mohd Muhyiddin Mustafa, Noritsugu Umehara, Nik Roselina Nik Roseley, Mohamad Ali Ahmad, Nor Azmmi Masripan

Jurnal Tribologi Vol. 43 page： 158 - 168 2024.6

Tribocatalytic Reaction Enabled by TiO<sub>2</sub> Nanoparticle for MoDTC-Derived Tribofilm Formation at ta-C/Steel Contact Reviewed International coauthorship International journal

COATINGS Vol. 14 ( 6 ) 2024.6

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

Tribochemically produced triboproducts are becoming increasingly important in tribosystems and serve to improve system performance by preventing friction or wear. Diamond-like carbon (DLC) is chemically stable, which features a trade-off with tribological pros and cons. Chemically stable DLC is thermally stable and suppresses surface damage in a high-temperature operating environment; however, it causes a detrimental effect that hinders the formation of a competent tribofilm. In this study, we dispersed highly reactive TiO2 nanoparticles (TDONPs) in molybdenum dithiocarbamate (MoDTC)-containing lubricant for adhering triboproducts on the DLC surface. In addition, TDONPs contributed to the decomposition of triboproducts by promoting the decomposition of MoDTC through its catalytic role. Rutile TDONPs were more helpful in reducing friction than anatase TDONPs and improved the friction performance by up to ~100%.

DOI： 10.3390/coatings14060773

Web of Science

Scopus

Super hardening of Fe-W alloy plating by phase transformation of amorphous to metal carbides-dispersed nanocrystalline alloys and application as promising alternative for hard chromium plating Reviewed International coauthorship

J.H. Park, J.I. Kim, Y. Shinohara, T. Hagio, N. Umehara, R. Ichino

SURFACE & COATINGS TECHNOLOGY Vol. 477 page： 130388 2024.5

Creation of anti-frost micro-plastic texture surfaces enhancing thermal conductivity by carbon black containing in polyvinyl chloride Reviewed

T. Tokoroyama, L. Zhang, W. Wu, M. Murashima, N.Umehara

Journal of Advanced Mechanical Design, Systems, and Manufacturing Vol. 18 ( 3 ) page： JAMDSM0032 2024.5

Effect of PAO-4 and MoDTC + ZnDTP oil additive lubricants on the tribological performance of novel tetrahedral amorphous carbon (ta-C) coatings Reviewed International coauthorship International journal

Mustafa M.M.B., Umehara N., Tokoroyama T., Murashima M., Utsumi Y., Moriguchi H., Shibata A.

TRIBOLOGY INTERNATIONAL Vol. 193 2024.5

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

This study was carried out to assess the effect of PAO-4 and mineral oil mixed with MoDTC and ZnDTP on the tribological performance of novel tetrahedral-amorphous-carbon (ta-C) coatings namely P:ta-C, and M:ta-C, were analysed using the Pin-on-Disk Tribo-tester with a fixed normal load, temperature, sliding distance and speed of 20 N, 80 °C, 250 m and 0.068 ms−1 for 60 min, respectively. The C:ta-C, P:ta-C, and M:ta-C showed excellent wear resistance when lubricated with MoDTC + ZnDTP. The formation of weak Zn-derived tribofilm on the P:ta-C coating contributed to the strong wear resistance and reduced friction coefficient. Moreover, the passive transfer of ferrous compounds from the SUJ2 disk induced the development of weak Zn-derived tribofilm on the P:ta-C and M:ta-C.

DOI： 10.1016/j.triboint.2024.109396

Scopus

The 1 μm wear particles entrainment in situ observation via fluorescent staining silica particles by silane coupling with Rhodamine B Reviewed

T. Tokoroyama, M. Okashita, N. Fusetani, M. Murashima, N. Hashizume, R. Tsuboi, H. Shiomi, N. Umehara

FRONTIERS IN MECHANICAL ENGINEERING-SWITZERLAND Vol. 10 page： 1371948 2024.4

The Influence of Succinimide Dispersant on the Formation of Tribofilm in ATF Friction Reviewed

TOKOROYAMA Takayuki, TERAI Yusuke, UMEHARA Noritsugu, MURASHIMA Motoyuki, HONDA Akiyuki, ADACHI Tsuneo

JOURNAL OF JAPANESE SOCIETY OF TRIBOLOGISTS Vol. advpub ( 0 ) 2024.3

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

<p>To elucidate the mechanism for suppressing wear of high-speed bearing steel (SUJ2) used in automatic transmission fluid (ATF), friction and wear tests were conducted in lubricating oils containing different concentrations of succinimide dispersant. The wear volume of the SUJ2 disk in the base oil was approximately 1.4×10⁴mm³. However, with the addition of 0.75 wt.% of succinimide dispersant, the wear volume decreased to about 0.4×10⁴mm³, approximately one-third of the original amount. In Fluid A and Fluid A I₀.₇₅-I₂.₇₅, the reduction in wear volume was observed only in Fluid A I₀.₇₅. This was believed to be due to the presence of succinimide dispersant, which led to the formation of iron oxide within the wear scars, and on the surface, FeS and FeS₂formed as tribofilms. In the case of Fluid A I₀.₇₅, the film hardness was higher, contributing to improved wear resistance. The sole reason for the increased hardness of the tribofilm in Fluid A I₀.₇₅was hypothesized to be the repeated friction of the tribofilm within the surface, leading to the deposition of FeS and FeS₂. This, in turn, was presumed to enhance the density of the tribofilm.</p>

DOI： 10.18914/tribologist.23-00021

CiNii Research

Lubricity performance of hydrogen-free CVD growth of graphene on copper particles as an additive in paraffin base oil Reviewed International coauthorship International journal

Rahman, NL; Amiruddin, H; Abdollah, MFB; Umehara, N

PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY Vol. 238 ( 7 ) page： 869 - 879 2024.3

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology

This study aims to examine the impact of carbon precursor materials, which are oil palm fiber (OPF) and waste polystyrene (PS), on friction and wear properties of paraffin base oil added with graphene-coated copper (Cu) additive. The graphene was synthesized on Cu particles via hydrogen-free chemical vapor deposition method. The graphene was characterized using Raman spectroscopy and transmission electron microscopy. The lubricity properties of 0.6 wt.% of synthesized graphene-coated Cu additive in paraffin base oil was analyzed based on its tribological behavior using a four-ball tribometer. From the quantitative and qualitative characterization analysis, graphene-coated Cu additive synthesized using 50 wt.% OPF carbon precursors has a good-quality graphene with minimal defects and a well-ordered lattice structure. From the tribological analysis, the paraffin base oil added with graphene-coated Cu additive synthesized using 50 wt.% OPF carbon precursor has the lowest coefficient of friction of 0.07 and wear rate of 1.6 × 10−5 mm3/min. Hence, it can be suggested that incorporating graphene-coated Cu particles, synthesized from a 50 wt.% OPF carbon precursor, into base oil shows great potential as an environmentally friendly additive, particularly in terms of enhancing lubrication performance.

DOI： 10.1177/13506501241236826

Web of Science

Scopus

The ta-C Hardness Effect on Wear Properties Under MoDTC Contained Boundary Lubrication Reviewed International coauthorship International journal

Tokoroyama, T; Wang, S; Umehara, N; Murashima, M; Lee, WY

TRIBOLOGY LETTERS Vol. 72 ( 1 ) 2024.3

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

The accelerated wear of hydrogenated amorphous carbon in the presence of molybdenum dithiocarbamate (MoDTC) lubrication is a significant challenge when considering its application in engine components. While it is presumed that the use of high-hardness tetrahedral amorphous carbon (ta-C) can effectively address wear issues, irrespective of chemical wear caused by Mo-degradable materials, we have yet to understand the impact of ta-C coating hardness on wear when combined with MoDTC. This uncertainty arises from the assumption that the quantity and structure of Mo-degradable material may be linked to contact pressure, implying that even with a highly hard ta-C coating, wear may vary with the applied load. In this study, we prepared ta-C coatings with four different hardness levels (such as approximately 18.2, 22.1, 46.6, and 53.6 GPa) and conducted friction tests to elucidate the influence of ta-C hardness on wear characteristics under boundary lubrication with MoDTC. Subsequently, we performed chemical analysis (Raman, EDS, and XPS) to identify the chemical species present in the tribofilm, with a particular focus on the 22.1 GPa ta-C coating as a representative of low-hardness ta-C coatings. Our findings revealed that wear suppression was achieved the contact pressure exceeded 200 MPa, irrespective of the coating hardness. Graphical abstract: [Figure not available: see fulltext.]

DOI： 10.1007/s11249-023-01804-6

Web of Science

Scopus

Clarification of the Effect of Surface Energy on Tribological Behavior of Two-Phase Lubricant Using Reflectance Spectroscopy and Hydrodynamic Analysis Reviewed International coauthorship International journal

Hirata, K; Murashima, M; Umehara, N; Tokoroyama, T; Lee, WY; Hashizume, N; Sato, T; Nagata, R; Hanyuda, K; Otsuka, A; Ueda, M

TRIBOLOGY LETTERS Vol. 72 ( 1 ) 2024.3

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

Recently, a new type of lubricant called two-phase lubricants has been developed to realize a high viscosity index. Two-phase lubricants are mixtures of two different lubricants, realizing low viscosity even at low temperatures due to the temperature dependence of the solubility of the lubricant molecules. In the present paper, the effect of surface energy on the tribological behavior of the two-phase lubricant is clarified using in situ observation with reflection spectroscopy. Sliding surfaces with high hydrogen-bonding terms in the surface energy components attracted high-polar lubricants, resulting in reduced friction. Analysis of the theoretical friction coefficient using Couette flow assumption revealed an important design concept of two-phase lubricants: the concentration of high viscosity lubricants on solid surfaces develops a viscosity distribution in the oil film, resulting in reduced friction.

DOI： 10.1007/s11249-023-01827-z

Web of Science

Scopus

Effect of the graphite domain direction on the friction coefficient of tetrahedral amorphous carbon nitride Reviewed International journal

Tokoroyama T., Fujiwara C., Murashima M., Yamaguchi M., Umehara N.

Diamond and Related Materials Vol. 143 2024.3

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Diamond and Related Materials

Polarized surface-enhanced Raman scattering was applied to low- and high- friction surfaces of tetrahedral amorphous carbon nitride (ta-CNx) to reveal the presence of the graphite structure and investigate the angular dependence of the graphite domains that formed on the topmost surface. The measured D peak intensity differed along the incident electric field toward the sliding direction, from parallel to perpendicular and armchair edges may be present. The results for the low- friction surface indicated that graphite domains exist on the ta-CNx disk and transfer layer on the counter material (Si3N4) ball in directions different from the sliding friction, which suggests an incommensurate configuration.

DOI： 10.1016/j.diamond.2024.110853

Scopus

In situ Observation of the Formation of MoDTC-Derived Tribofilm on a Bearing Steel with Different Surface Roughness by Using a Reflectance Spectroscopy and Its Effects on Friction Reviewed International coauthorship International journal

Hashizume, N; Tokoroyama, T; Umehara, N; Murashima, M; Lee, WY; Zhang, RX; Kunisu, M; Shioji, H; Oharada, K

TRIBOLOGY LETTERS Vol. 72 ( 1 ) 2024.3

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

In this paper, we evaluated the formation of MoDTC-derived tribofilm and its effects on friction reduction. We conducted in situ observation using reflectance spectroscopy to monitor the tribofilm's evolution during friction, allowing us to estimate its thickness and composition. The results revealed that the rough specimen (Ra= 12.7 nm) maintained a smaller friction coefficient and a larger volume fraction of MoS2 compared to the smooth specimen (Ra= 2.6 nm). Additionally, using the in situ observed composition and contact state, we inferred changes in the frictional properties of the tribofilm formed on both specimens. This analysis suggested that the pronounced direct contact of asperities, especially evident in the rough specimen, promoted the formation of a low-friction tribofilm (primarily MoS2), enabling the rough specimen to sustain lower friction. Graphical abstract: [Figure not available: see fulltext.].

DOI： 10.1007/s11249-023-01810-8

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Scopus

Synthesising graphene with renewably-sourced bio-carbon precursors: a brief review Reviewed International coauthorship International journal

Abd Rahman F.H., Amiruddin H., Abdollah M.F.B., Mohd Zulkifli N.W., Samion S., Umehara N., Tanemura M., Honda M., Morina A.

Journal of the Brazilian Society of Mechanical Sciences and Engineering Vol. 46 ( 3 ) 2024.3

The Effect of Carbon Structure of DLC Coatings on Friction Characteristics of MoDTC-Derived Tribofilm by Using an In Situ Reflectance Spectroscopy Reviewed International coauthorship International journal

Hashizume, N; Yamamoto, Y; Chen, C; Tokoroyama, T; Zhang, RX; Diao, DF; Umehara, N

TRIBOLOGY LETTERS Vol. 72 ( 1 ) 2024.3

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Papers - UMEHARA, Noritsugu