Effect of Graphite Content on Cu–Ni–Graphite Composite for Use as Switch Slide Baseplate Materials Sliding Against U75V Steel

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Yiran Wang ◽  
Yimin Gao ◽  
Jun Takahashi ◽  
Yi Wan ◽  
Yunqian Zhang ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Wear Mechanism ◽  
High Speed ◽  
Sliding Friction ◽  
Rapid Development ◽  
Wear Volume ◽  
Fatigue Wear ◽  
Friction Coefficients ◽  
Graphite Composite ◽  
Graphite Content

Abstract The rapid development of high-speed railways necessitates the development of new materials for switch slide baseplates. In this study, a Cu–Ni–graphite composite, containing 1 wt% to 6 wt% graphite and prepared by powder metallurgy, was used as a potential material. Pin-on-disk wear tests were conducted to measure the sliding friction of the Cu–Ni–graphite composite against U75 V steel. The results showed that the friction coefficients gradually decreased when the graphite content in the composite ranged from 1 wt% to 4 wt% in the composite. When the graphite content was 4 wt%, the friction coefficient reached the minimum value (0.153). When the graphite content was low (1 wt% to 4 wt%), the primary wear mechanism was microcutting. An increased graphite content facilitated the generation of lubricating films and decreased the wear damage. As the graphite content increased from 4 wt% to 6 wt%, the friction coefficients also increased. The variation in the wear volume rate had the same tendency as the friction coefficient. When the graphite content exceeded 4 wt%, the primary wear mechanism was delamination and fatigue wear. Due to the tendency to form cracks on the subsurface and the plentiful generation of the spalled pits, the graphite fragments could not completely form lubricating films but separated as wear debris. The lubricating films existing on the U75 V steel were in proportion to the graphite content in the composite. The wear weight loss of the U75 V steel exhibited a reduction with increasing graphite content.

scholarly journals Wear Behavior of Copper–Graphite Composites Processed by Field-Assisted Hot Pressing

2019 ◽  
Vol 3 (1) ◽  
pp. 29 ◽  
Author(s):  
Qian Liu ◽  
Miguel Castillo-Rodríguez ◽  
Antonio Galisteo ◽  
Roberto Guzmán de Villoria ◽  
José Torralba
Keyword(s):  
Friction Coefficient ◽  
Wear Mechanism ◽  
Hot Pressing ◽  
Normal Load ◽  
Pure Copper ◽  
Wear Testing ◽  
Critical Threshold ◽  
Graphite Composite ◽  
Graphite Content ◽  
Graphite Composites

Copper–graphite composites with 0–4 wt % graphite were fabricated by field-assisted hot pressing with the aim of studying the effect of graphite content on microhardness and tribological properties. Experimental results reveal that hardness decreases with the graphite content. Wear testing was carried out using a ball-on-disc tribometer with a normal load of 8 N at a constant sliding velocity of 0.16 m/s. The friction coefficient of composites decreases significantly from 0.92 to 0.29 with the increase in graphite content, resulting in a friction coefficient for the 4 wt % graphite composite that is 68.5% lower than pure copper. The wear rate first increases when the graphite content is 1 wt %; it then decreases as the graphite content is further increased until a certain critical threshold concentration of graphite, which seems to be around 3 wt %. Plastic deformation in conjunction with some oxidative wear is the wear mechanism observed in pure copper, while abrasive wear is the main wear mechanism in copper–graphite composites.

scholarly journals Dry Rolling/Sliding Wear of Bainitic Rail Steels under Different Contact Stresses and Slip Ratios

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4678
Author(s):  
Jiapeng Liu ◽  
Yingqi Li ◽  
Yinhua Zhang ◽  
Yue Hu ◽  
Lubing Shi ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Abrasive Wear ◽  
Contact Stress ◽  
Wear Mechanism ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Wear Loss ◽  
Fatigue Wear ◽  
Slip Ratio

This study aims to deeply understand the effect of contact stress and slip ratio on wear performances of bainitic rail steels. The results showed that the wear loss increased as the contact stress and slip ratio increased. Based on the surface damage morphology and microstructural analyses, it revealed that the rolling contact fatigue wear mechanism played a significant role under the low slip ratio, but the dominant wear mechanism transferred to the abrasive wear at the high slip ratio. Meanwhile, the bainitic steel specifically presented worse wear resistance under the abrasive wear mode. Compared with the influence of a slip ratio, the increase in contact stress led to severer plastic flows and contributed to the propagation of cracks. In addition, the contact stress and slip ratio had the opposite effect on the friction coefficient, that is, the friction coefficient of bainitic steels behaved the inverse proportion with the contact stress, but positive proportion with the slip ratio. At last, the increase in slip ratio had more significant effect on the reduction of retained austenite (RA) than the enlargement of contact stress due to the fact that the RA would probably be removed before the martensitic transformation occurred under the abrasive wear mechanism.

scholarly journals Effect of Polypropylene Modification by Impregnation with Oil on Its Wear and Friction Coefficient at Variable Load and Various Friction Rates

2017 ◽  
Vol 2017 ◽  
pp. 1-19 ◽  
Author(s):  
Paweł Sędłak ◽  
Beata Białobrzeska ◽  
Tomasz Stawicki ◽  
Piotr Kostencki
Keyword(s):  
Friction Coefficient ◽  
Sliding Friction ◽  
Wear Test ◽  
Friction Torque ◽  
Engine Oil ◽  
Wear Testing ◽  
Wear Behaviour ◽  
Linear Wear ◽  
Variable Load ◽  
Fatigue Wear

Laboratorial two-body wear testing was carried out in order to assess effects of polypropylene modification by impregnating it with oils on friction coefficient and wear in comparison to those parameters of unmodified polypropylene, Teflon, and polyamide during operation under conditions of sliding friction without lubrication. Wear behaviour of the tested specimens was investigated using ASTM G77-98 standard wear test equipment. Recording program made it possible to visualise and record the following parameters: rotational speed and load, linear wear, friction coefficient, temperature of the specimen, and ambient temperature. In addition, wear mechanisms of the analysed materials were determined with use of scanning electron microscopy. In the case of the remaining tested polymers, the most important mechanism of wear was adhesion (PP, PTFE, PA 6.6, and PA MoS2), microcutting (PTFE, PA 6.6, and PA MoS2), fatigue wear (PTFE), forming “roll-shaped particles” combined with plastic deformation (PA 6.6 and PA MoS2), and thermal wear (PP). Impregnation of polypropylene with engine oil, gear oil, or RME results in significant reduction of friction coefficient and thus of friction torque, in relation to not only unmodified polypropylene but also the examined polyamide and Teflon.

The Friction and Wear Properties of VC Coating by TD Process

2010 ◽  
Vol 33 ◽  
pp. 61-65 ◽  
Author(s):  
Chao Zheng Zhou ◽  
De Jun Kong ◽  
Yu Feng Yan
Keyword(s):  
Crack Growth ◽  
Wear Mechanism ◽  
High Speed ◽  
Friction And Wear ◽  
Cold Working ◽  
Mutual Influence ◽  
Wear Properties ◽  
Fatigue Wear ◽  
Friction And Wear Properties ◽  
Surface Morphologies

VC coating was prepared on the surface of Cr12MoV cold working die steel by TD process, and its friction and wear properties were researched with HSR-2M type high-speed reciprocating friction and wear tester, the effects of load on friction and wear properties were discussed, and the wear surface morphologies were observed with SEM. The experimental results shown that fatigue wear and adhesive wear are mainly wear mechanism of VC coating, and the different parts have an influence on wear mechanism; When cracks occurs, the crack growth is the combined result of mutual influence of elastic-plastic crack growth and fatigue crack growth; There is no relationship between friction coefficient and load, and the wear rate increases with the load.

scholarly journals Effects of Temperature on the Tribological Properties of NM600 under Sliding Wear

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4009
Author(s):  
Yingchao Pei ◽  
Dianxiu Xia ◽  
Shouren Wang ◽  
Liang Cong ◽  
Xuelin Wang ◽  
...  
Keyword(s):  
Abrasive Wear ◽  
Tribological Properties ◽  
Wear Mechanism ◽  
Adhesive Wear ◽  
Wear Volume ◽  
Fatigue Wear ◽  
Matrix Properties ◽  
Different Temperatures ◽  
Effects Of Temperature ◽  
Oxidation Wear

An investigation on the tribological properties of GCr15 sliding against NM600 was carried out using a high-temperature friction and wear tester. As the temperature rose from room temperature to 300 °C, the average friction coefficient of NM600 increased rapidly, then decreased rapidly, and then became stable. The wear volume and specific wear rate of NM600 increased rapidly, then decreased rapidly, and then increased slowly. The wear mechanism and matrix properties of the tested steel at different temperatures are the main reasons for the above results. At 20–50 °C, the main wear mechanism was adhesive wear, fatigue wear, and abrasive wear. At 100–150 ℃, the wear mechanism was mainly adhesive wear, fatigue wear, abrasive wear, and oxidation wear. At 200–300 °C, the wear mechanism was mainly oxidation wear and abrasive wear.

Tribological behaviors of precipitates reinforced Cr-Ni-Mo-V steel lubricated by water or water-silica mixture

2018 ◽  
Vol 70 (8) ◽  
pp. 1431-1436 ◽  
Author(s):  
Shuaishuai Zhu ◽  
Baosen Zhang ◽  
Zhixin Ba ◽  
Xiangyang Mao ◽  
Weijie Fei ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
High Speed ◽  
Brake Disc ◽  
Wear Properties ◽  
Fatigue Wear ◽  
Industrial Firms ◽  
Content Type ◽  
Liquid Cell ◽  
Braking Process ◽  
Worn Surface

Purpose This paper aims to investigate the friction and wear properties of Cr-Ni-Mo-V steel against 440C stainless steel under both water and water–silica mixture lubricant. Design/methodology/approach The Cr-Ni-Mo-V steel specimens were taken from a forged steel brake disc with the process of quenching at 900°C and tempering at 600°C. The tribological testing was performed using a contact configuration of ball-on-flat with a liquid cell according to the ASTM standard. Detailed examinations on the worn surface were analyzed using a scanning electron microscope. Findings The results indicate that the friction coefficient and friction damage of the steel sliding under water–silica mixture are higher than those under water. The friction coefficient decreases with increasing load and increases with the sliding speed for the two lubricants. The mass wear rate presents a rising trend with both sliding load and speed. The wear mechanisms of the Cr-Ni-Mo-V steel sliding under the two lubricants are oxidation wear, abrasive wear and fatigue wear. Research limitations/implications Because of the chosen tribological testing approach, the research results could not describe the tribological performance of the brake disc accurately during actual braking process of the high-speed train. Therefore, researchers are encouraged to test the proposed propositions further. Originality/value This study shows that the tribology behavior of the Cr-Ni-Mo-V steel with water or water–silica mixture lubrications helps the industrial firms and academicians to work on the wear of the brake disc in rainwater or wet environment.

The Performance Of Semi–Metallic Friction Materials For Passenger Cars

2012 ◽  
Author(s):  
Ria Jaafar Talib ◽  
Andanastuti Muchtar ◽  
Che Husna Azhari
Keyword(s):  
Steady State ◽  
Friction Coefficient ◽  
Surface Temperature ◽  
Wear Mechanism ◽  
Morphological Changes ◽  
Wear Behaviour ◽  
Wear Volume ◽  
Brake Disc ◽  
Passenger Cars ◽  
Metallic Friction

Dalam kajian ini, penilaian haus mekanikal ke atas bahan geseran separa logam untuk kegunaan kereta penumpang dikaji dengan menekan sampel kepada piring yang berpusing diperbuat daripada besi tuang kelabu pearlitik. Bagi setiap ujian, sampel dikenakan empat jangka masa pembrekan (3, 6, 9, dan 12 minit) dan empat beban kenaan (200, 400, 600 dan 800 N) yang berlainan. Kelajuan putaran piring brek dikekalkan malar sepanjang pengujian geseran pada 750 psm. Selepas setiap ujian, perubahan morfologi permukaan dan subpermukaan diperhatikan dengan menggunakan mikroskop elektron imbasan (MEI). Hasil kajian menunjukkan ciri-ciri berikut: (i) suhu permukaan meningkat dengan masa pembrekan dan selepas mencapai nilai maksimum, akhirnya sampai kepada keadaan stabil, (ii) pekali geseran telah meningkat pada permulaan pembrekan, kemudian menurun dengan masa pembrekan, dan seterusnya sampai kepada keadaan stabil, dan (iii) isipadu haus meningkat secara lelurus apabila beban kenaan di bawah 200 N dan/atau masa pembrekan di bawah 3 minit dan kedua-duanya seterusnya meningkat secara eksponen. Pemeriksaan mikrostruktur menunjukkan mekanisme haus beralih dengan peningkatan jangka masa pembrekan dan beban kenaan. Fenomena ini juga menyebabkan perubahan kepada sifat haus. Kata kunci: Pad brek, suhu permukaan, pekali geseran, haus, mekanisme haus In this work, a semi-metallic friction material for passenger cars was evaluated for mechanical wear by pressing the material against a rotating pearlitic gray cast iron brake disc. In each test, the sample was subjected to four different braking times (3, 6, 9, and 12 minutes) and four applied loads (200, 400, 600 and 800 N). The rotating velocity of the disc was kept constant throughout the friction tests at 750 rpm. After each test, the morphological changes on the surface and subsurface of the material were observed using Scanning Electron Microscopy (SEM). The following characteristics were observed: (i) the surface temperature increased with braking time and after reaching a maximum value, eventually arrived at a steady state, (ii) the friction coefficient increased at the early stages of braking, then decreased with braking time and thereafter reached steady state, and (iii) the wear volume increased linearly when the applied load was below 200 N and/or braking time was below 3 minutes or both, thereafter the volume increased exponentially. Microstructural examinations showed that the wear mechanism transisted with increase in braking times as well as applied loads. This phenomenon also resulted in changes of the wear behaviour. Key words: Brake pad, surface temperature, friction coefficient, wear, wear mechanism

Friction and Wear Behaviors of WC-Co/WC-Co Pairs in Air

2007 ◽  
Vol 534-536 ◽  
pp. 1193-1196
Author(s):  
Hiroyuki Hosokawa ◽  
Takeshi Nakajima ◽  
Koji Shimojima
Keyword(s):  
Friction Coefficient ◽  
Diffraction Pattern ◽  
Wear Debris ◽  
Friction And Wear ◽  
Sliding Friction ◽  
Wear Test ◽  
Wear Volume ◽  
Grain Sizes ◽  
Ball On Disc

To investigate sliding friction and wear behaviors of WC–Co/WC–Co pairs containing different WC grain sizes, the ball-on-disc test in air were carried out for WC-Co containing WC grain sizes of 0.5 μm (F.G.) and 1.5 μm (C.G.). The results show that the wear volume of F.G. pin for F.G. pin/C.G. disc is larger than that of F.G. pin for F.G. pin/F.G. disc due to higher friction coefficient, and the surfaces after wear test are richer in oxygen compared to those before test. Furthermore, the wear debris, which is composed of nona-scale grains, after the wear test are remarkably richer in oxygen than to those before test. The diffraction pattern reveals sharp ring

An Experimental Investigation on Wear of Rail in Different Curve Radius

2013 ◽  
Vol 739 ◽  
pp. 458-461
Author(s):  
W. Zhong ◽  
P. Chen ◽  
Y. Wang
Keyword(s):  
Plastic Deformation ◽  
Fatigue Crack ◽  
High Speed ◽  
Fatigue Behavior ◽  
Wear Volume ◽  
Fatigue Wear ◽  
Propagation Angle ◽  
Wear Process ◽  
Railway Rail ◽  
Curve Radius

Among the rail defects, the transverse fatigue crack, which has been the most dangerous damage, is developed near the rail running face and grows perpendicular to the rail surface. Finally, the transverse fatigue crack would result in the failure of railway rail. In this paper, the rolling tests were performed using a JD-1 wheel/rail simulation facility without any lubricant. The tester is composed of a small wheel served as rail and a larger wheel served as wheel. The fatigue behavior of rail rollers with different materials and curve radius were investigated in detail by examining wear volume and wear scar using optical microscopy (OM) and scanning electronic microscopy (SEM). The results indicate that with curve radius decreasing, the wear volume of rail roller increases rapidly and the fatigue damage becomes severe. Furthermore, the cracking propagation angle increases obviously with curve radius decreasing and fatigue wear is dominating during the wear process. There appears distinct plastic deformation on the section of rail roller under small curve radius condition. For the same curve radius, the wear volume of PD3 rail is more than that of PG4 rail and the plastic deformation is more obvious. Moreover, the cracking propagation angle of PD3 rail material is smaller than that of PG4 rail. In conclusion, PG4 rail material is not suitable for the high-speed railway.

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