TRIBOLOGICAL STUDY OF SELF-LUBRICATING COMPOSITES WITH HEXAGONAL BORON NITRIDE AND GRAPHITE AS SOLID LUBRICANTS

Abstract High-velocity oxyfuel (HVOF) sprayed coatings of Cr3C2-NiCr containing solid lubricants such as nickel cladded graphite and hexagonal boron nitride were successfully developed and characterised with the aim of optimizing their friction and wear behaviour. HVOF technology was used for the integration of solid lubricants to achieve strong cohesion between particles while minimizing thermal decomposition. Coating microstructure and composition were measured and correlated to the results of tribological and corrosion tests. The integration of the solid lubricant greatly reduced friction and wear volume at room temperature, but the lubricating effect was highly dependent on atmosphere and temperature. Cr3C2-NiCr with hBN, however, tends to exhibit more stable wear resistance over a wider temperature range and can be used at temperatures beyond 450 °C.

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Investigation on Microstructure Characteristics and Tribological Properties of Self-Lubricating Metallic Composites Based on Hexagonal Boron Nitride and Molybdenum Disulphide

Journal of Tribology ◽

10.1115/1.4047948 ◽

2020 ◽

Vol 143 (2) ◽

Author(s):

Biao Zhao ◽

Wenfeng Ding ◽

Guohua Jiang ◽

Xianying Li ◽

Jiuhua Xu

Keyword(s):

Boron Nitride ◽

Flexural Strength ◽

Hexagonal Boron Nitride ◽

Metallic Matrix ◽

Solid Lubricants ◽

Tribological Performance ◽

Liquid Phase Sintering ◽

Molybdenum Disulphide ◽

Microstructure Characteristics ◽

Metallic Composites

Abstract In this work, hexagonal boron nitride (hBN)- and molybdenum disulphide (MoS2)-embedded metallic composites were fabricated via liquid-phase sintering. The mechanical property and tribological performance of different samples that contain 5, 7.5, 10, 12.5, and 15 wt% solid lubricants were evaluated. Morphologies, such as micropores and ball and scratch, were characterized after the rotating sliding tests. A high lubricant concentration could adversely affect the flexural strength of as-sintered samples because of the formation and coalescences of micropores. In comparison with MoS2-containing samples under the same lubricant concentrations, the hBN-containing samples exhibited lower flexural strength and density caused by amounts of spherical small and irregular large micropores. Furthermore, the best tribological combination could be achieved in terms of the friction coefficient, wear-rate, and morphologies of balls by applying 7.5 wt% MoS2 particles in the metallic matrix.

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Grinding Capability of the Indigenous Polymer-Based Solid Lubricant Coating Wheels Used in Dry Grinding

Materials Science Forum ◽

10.4028/www.scientific.net/msf.697-698.80 ◽

2011 ◽

Vol 697-698 ◽

pp. 80-83

Author(s):

L.Y. Ding ◽

Hong Hua Su ◽

H.J. Xu ◽

M. Fan

Keyword(s):

Boron Nitride ◽

Surface Quality ◽

Solid Lubricant ◽

Hexagonal Boron Nitride ◽

Solid Lubricants ◽

Grinding Temperature ◽

Solid Lubricant Coating ◽

Lubricant Coating ◽

Dry Grinding

It is essential to control the heat generated in the cutting zone in order to ensure the workpiece quality after grinding. This article deals with an investigation in using graphite and hexagonal boron nitride as solid lubricants to reduce friction and thereby improve the surface integrity of Ti-6Al-4V alloy. The polymer-based solid lubricant coating wheels have been prepared. Grinding experiments have been conducted to study the effect of the graphite and hexagonal boron nitride lubricants on the grinding temperature and the surface quality of the workpiece while grinding Ti-6Al-4V. Results indicate that there is a considerable improvement in the performance of grinding Ti-6Al-4V using graphite and hexagonal boron nitride as solid lubricants in dry grinding in terms of grinding temperature and surface quality of the work piece. The indigenous polymer-based solid lubricant coatings are effective in dry grinding.

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An Experimental Evaluation of Solid Lubricant Based Nanofluids in Small Quantity Cooling and Lubrication during Grinding

Materials Science Forum ◽

10.4028/www.scientific.net/msf.890.98 ◽

2017 ◽

Vol 890 ◽

pp. 98-102 ◽

Cited By ~ 1

Author(s):

Sourabh Paul ◽

Amitava Ghosh

Keyword(s):

Boron Nitride ◽

Solid Lubricant ◽

Hexagonal Boron Nitride ◽

Solid Lubricants ◽

Metallic Alloys ◽

Grinding Wheel ◽

Metal Working ◽

Maximum Reduction ◽

Cooling And Lubrication ◽

Ball On Disc

Small quantity cooling lubrication (SQCL) with commercially available metal working fluids (MWF) and nanofluids has been attempted successfully in machining and grinding. Solid lubricants also provided some benefits in grinding of metallic alloys. However, there are very few studies using molybdenum di-sulphide (MoS2) and hexagonal boron nitride (hBN) dispersed nanofluids applied in SQCL mode in grinding. The aim of the present work is to experimentally study improvement in grinding of EN31 steel using alumina grinding wheel with aqueous MoS2 and hBN nanofluids. The grinding study is supported by detailed tribometry at 1 m/s sliding speed to reveal the possible reasons behind such improvement. MoS2 dispersed nanofluids provided minimum coefficient of friction in ball-on-disc test. It also provided the maximum reduction in specific grinding energy and improvement in surface finish with respect to flood cooling. hBN dispersed nanofluids could not match the performance of MoS2 dispersed nanofluids both in ball-on-disc and grinding experiments.

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Effect of Liquid Phase during Sintering on Mechanical and Tribological Properties of Self-Lubricating Composites

Materials Science Forum ◽

10.4028/www.scientific.net/msf.899.523 ◽

2017 ◽

Vol 899 ◽

pp. 523-527 ◽

Cited By ~ 1

Author(s):

Renata Steinbach ◽

Tatiana Bendo ◽

G. Hammes ◽

C. Binder ◽

J.D.B. de Mello ◽

...

Keyword(s):

Tensile Strength ◽

Liquid Phase ◽

Friction Coefficient ◽

High Performance ◽

Hexagonal Boron Nitride ◽

Solid Lubricants ◽

Liquid Phase Sintering ◽

Mechanical And Tribological Properties ◽

The Matrix ◽

Self Lubricating Composites

The present work aimed to contribute to the development of high performance self-lubricating sintered composites, with low friction coefficient and high mechanical strength. Self-lubricating composites presenting embedded solid lubricants in a ferrous matrix were produced. Hexagonal boron nitride (hBN) and graphite were the solid lubricants powders added during the mixing step. The composites were processed by conventional powder metallurgy. The liquid phase sintering, by adding copper, improved the degree of continuity of the matrix by rearranging the solid lubricant particles. With this, besides the hardening effect on the matrix, the mechanical properties of the composites were improved, with tensile strength increasing when compared to the same composite without copper. By using the proposed methodologies, optimized composites presenting friction coefficient of 0.12, tensile strength of 500 MPa and scuffing resistance of 29300 N.m were obtained.

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NUCLEATE POOL BOILING AND CONDENSATION HEAT TRANSFER CHARACTERISTICS OF HEXAGONAL BORON NITRIDE/DICHLOROMETHANE NANOFLUID

Heat Transfer Research ◽

10.1615/heattransres.2020034308 ◽

2020 ◽

Vol 51 (11) ◽

pp. 1043-1059

Author(s):

Erdem Çiftçi ◽

Adnan Sözen

Keyword(s):

Heat Transfer ◽

Boron Nitride ◽

Hexagonal Boron Nitride ◽

Pool Boiling ◽

Condensation Heat Transfer ◽

Nucleate Pool Boiling ◽

Heat Transfer Characteristics ◽

Transfer Characteristics

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Marcus-Hush Theory Revealed by Electron Tunneling Through Hexagonal Boron Nitride

10.26434/chemrxiv.9275135.v1 ◽

2019 ◽

Author(s):

Matěj Velický ◽

Sheng Hu ◽

Colin R. Woods ◽

Peter S. Toth ◽

Viktor Zólyomi ◽

...

Keyword(s):

Electron Transfer ◽

Boron Nitride ◽

Electron Tunneling ◽

Hexagonal Boron Nitride ◽

Large Body ◽

Liquid Solution ◽

Limiting Current ◽

Electron Transfer Rate Constant ◽

Electrochemical Parameters ◽

Voltammetric Measurements

Marcus-Hush theory of electron transfer is one of the pillars of modern electrochemistry with a large body of supporting experimental evidence presented to date. However, some predictions, such as the electrochemical behavior at microdisk electrodes, remain unverified. Herein, we present a study of electron tunneling across a hexagonal boron nitride barrier between a graphite electrode and redox levels in a liquid solution. This was achieved by the fabrication of microdisk electrodes with a typical diameter of 5 µm. Analysis of voltammetric measurements, using two common redox mediators, yielded several electrochemical parameters, including the electron transfer rate constant, limiting current, and transfer coefficient. They show a significant departure from the Butler-Volmer behavior in a clear manifestation of the Marcus-Hush theory of electron transfer. In addition, our system provides a novel experimental platform, which could be applied to address a number of scientific problems such as identification of reaction mechanisms, surface modification, or long-range electron transfer.

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