Surface Of Balls Research Articles

Preparation of Ti–MoS2 coating and gradient structure via mechanical ball milling to improve the wear resistance of AISI 440C stainless steel bearing balls

Owing to its excellent wear resistance and high hardness, 440C stainless steel is widely used in the manufacturing of bearing steel balls. However, in high-speed and heavy-duty environments, bearing steel balls are prone to wear and failure, which affect their service life. This study focused on 440C stainless steel bearing balls and developed a method for preparing Ti–MoS2 coatings and nano gradient structures on the surface of the steel balls via mechanical ball milling so as to improve their wear resistance. A detailed experimental study regarding the surface microstructure and friction performance of the processed balls was simultaneously conducted. The results demonstrated that the surface of the treated bearing steel ball formed a nano gradient structure and a 4 μm Ti–MoS2 coating. The surface roughness of the treated sample decreased by 9.2% and the surface microhardness (831.9 ± 6.4 HV) increased by 28.93% compared to that of the untreated sample. The friction and wear experiments demonstrated that under a load of 80 N, the wear of the treated bearing steel balls decreased by 51.23% compared to that of the untreated bearing steel balls (9.94 ± 0.41) × 106 μm3. Our findings indicate that preparing Ti–MoS2 coatings and nano gradient structures on the surface of steel balls via mechanical ball milling is an effective approach to improving the friction performance of bearing steel balls.

Improving the wear resistance of 440C bearing steel balls by adding ZrO2 in mechanical alloying

The wear resistance of 440C bearing steel balls significantly impacts the reliability of bearings. Our method for increasing the wear resistance of steel balls combines mechanical alloying to create nanogradient structures with ZrO2 doping on the surface of the steel balls. The results revealed that ZrO2 formed mechanical alloying on the surface of the steel balls. Under all loads, the processed samples exhibited excellent wear resistance. Compared to untreated samples, the wear of processed samples subjected to 20, 40, and 60 N loads decreased by 28.82 %, 50.25 %, and 50.79 %, respectively. The existing literature indicates that adding ZrO2 powder during mechanical alloying is a promising method for improving the friction performance of bearing steel balls.

Study on the effect of anti-oxidation film formed by composite system on solder balls performance

In this paper, an anti-oxidation film was formed on the surface of Sn3.0Ag0.5Cu solder balls by using a composite system of benzotriazole (BTA) and 2-aminobenzimidazole (2-ABT). The properties of anti-oxidation film were measured by shaking balls test, shearing strength test and cavity test. The results showed that when the combination of 1.5 g/L BTA and 0.5 g/L 2-ABT was used to form an anti-oxidation film on the surface of solder balls, the life of the solder balls surface without dendrite wear during shaking balls test was increased by 10 times, and the cavity rate was decreased from 5 % to 3 %, resulting in that the shear strength of the solder joint was increased from 20.96 MPa to 40.45 MPa. And the theoretical calculation results showed that N2 atoms of benzotriazole and 2-aminobenzimidazole molecules were the most active and adsorbed on the surface of the solder balls to form anti-oxidation films.

Tribological Properties of Groove-Textured Ti-6Al-4V Alloys with Solid Lubricants in Dry Sliding against GCr15 Steel Balls.

A nanosecond laser is used to fabricate groove-patterned textures on the upper surface of Ti-6Al-4V alloys, and then molybdic sulfide solid lubricants are filled into the grooves. The treated titanium alloy is subjected to friction and wear tests. The tribological performances of Ti-6Al-4V alloys are evaluated, and the wearing mechanism is analyzed. The combination of solid lubricants and surface texturing can effectively reduce the frictional coefficient and reduce the adhesion of Ti-6Al-4V materials on the steel balls for friction. The main wearing mechanism is the adhesive wear of the Ti-6Al-4V alloy and the adhesion of Ti-6Al-4V alloy materials on the surface of the steel balls. During the friction process, solid lubricants are squeezed from the grooves and coated at the friction interface to form a solid lubrication layer. This is the important reason why the combination of surface texturing and solid lubricants can improve the friction properties of titanium alloys effectively. The combination of solid lubricants and laser surface texturing provides an effective alternative way to improve the tribological properties of titanium alloy materials.

Investigate on the dry friction tribological behaviors and mechanism of carbon quantum dot/polyimide composites coating

The comprehensive utilization of biomass resources is to be prepared into functional nanomaterial. This paper prepared carbon quantum dots (CQDs) using citric acid. A new CQDs/polyimide composites (CQDs/PI) coating fabricated on the surface of steel disks, has been widely used in bearing sleeve material or coatings in marine equipment parts and aerospace industries. Tribological properties of coating materials were investigated at different loads and reciprocating speeds of 10 mm/s under dry sliding conditions using a UMT-2 tribometer and compared to those of commercial MoS2 particles in PI composites. Scanning electron microscopy accompanied by energy spectroscopy (SEM/EDS) and 3D laser scanning microscopy were used to characterize the morphologies of the abrasion marks to clarify the tribological mechanisms. Results show that different levels of CQDs can improve composite coatings' anti-wear and friction reduction properties. The tribological mechanisms of CQDs were attributed to the enhancement of the hardness of the polyimide coatings by the CQDs and the formation of a transfer film on the surface of the ceramic balls during the friction process reducing the direct contact at the friction sub-interface.1

Retraction Note: Application of deep learning to detect defects on the surface of steel balls in an IoT environment

Retraction Note: Application of deep learning to detect defects on the surface of steel balls in an IoT environment

Tribological behavior and mechanical properties of thermal sprayed TiO2–ZnO and TiOx ceramic coatings

The tribological behaviors of TiO2–ZnO and TiOx coatings deposited by atmospheric plasma spraying were studied to further explore the immanent tribological performance of the oxide system at high temperatures. The results show that both the plasma spraying fabrication process and the high temperature sliding process will lead to the phase transformation of the ceramic coatings. The tribological properties of TiO2–ZnO and TiOx ceramic coatings are temperature-dependent and can be improved with the increase in temperature except that of the TiO2–ZnO coating at 400 °C. The lower friction coefficients and wear rates of TiO2–ZnO coatings and TiOx coating at 800 °C are mainly related to the smooth film formation on both the worn surface of coatings and counterpart balls, consisting of high temperature lubricating oxides (A-TiO2, R–TiO2, Zn2TiO4, and Ti8O15).

Improved wear properties of GCr15 steel balls by fabricating a surface Ti diffusion layer using mechanical alloying and NH3·H2O treatment

This work used mechanical alloying combined with NH3·H2O treatment to strengthen GCr15 steel balls. First, GCr15 steel balls with a Ti coating were fabricated by mechanical alloy considering two structures of jars: one is the ordinary jar and the second is self-made special jar (SMA). Then, the deposited Ti coatings were removed by dropping NH3·H2O during the ball milling process. Surprisingly, a Ti diffusion layer is obtained on the surface of GCr15 steel balls. In particular, the Ti diffusion layers in the samples processed by self-made special jars show a thickness of approximately 3.2 μm. Mechanical Properties, such as grain, dislocation, microhardness, and friction coefficient of the processed samples, were investigated. Results show that a hardening layer of approximately 120 μm is formed on the samples processed by self-made special jars, which increased by 129% than that of samples processed by ordinary jar. A microhardness as high as 895 HV is also realized on sample surface, where obvious grain refinement and larger dislocation density were observed. The possible working mechanism was discussed. This study demonstrated that the proposed method could significantly improve the fatigue life of some mechanical components, especially for steel balls.

Effect of the Sliding Element Surface Topography on the Oil Film Thickness in EHD Lubrication in Non-Conformal Contact.

Under hard operating conditions such as high load, low speed and a lack of a sufficient quantity of lubricant, the sliding pairs could suffer serious damage. One of the methods that improves the tribological performance of sliding elements in hard operating conditions is the appropriate surface creation that keeps lubricating substance in cavities. This article presents the results obtained in experimental investigations of the oil film thickness in lubricated non-conformal contact with a different surface topography of the sliding element. The tests were conducted on a ball-on-disc instrument equipped with colorimetric interferometry. Balls of diameter equaled to 19.05 mm were produced from 100 Cr6 steel. To provide hard operating conditions, the glass disc rotated at small speeds in the range of 0.1-0.2 m/s. The tests were carried out at loads of 20 N and 30 N. As a result, in most cases, the highest minimum and average oil film thickness values were obtained when the surface of steel balls was characterized by high negative asymmetry with mainly shallow cavities and some valleys of great depth compared to the height of the peaks. The modified sliding surface that had better performance comprised a comparatively small number of peaks and the curvature of the peaks were large.

The Effect of the Displacement Amplitude on the Fretting Wear of GCr15 Steel with a TiC Coating.

In the present paper, the effect of mechanical ball milling time on the fretting wear of GCr15 steel balls at different displacement amplitudes is investigated. TiC powder coating was fabricated on the surface of GCr15 steel balls using various process times, and the fretting wear tests were conducted on an AISI 52100 steel disk with the applied force of 80 N. Additionally, various displacement amplitudes (10 μm, 20 μm, and 60 μm) were selected. Specimen attributes and wear scars were characterized using an inverted metallographic microscope, a microhardness tester, an X-ray diffractometry analyzer, a white light interferometer, and a scanning electron microscope. The results showed that thick and continuous coatings could be obtained at the milling time of 18 h. The specimens processed for a longer milling time demonstrated better fretting wear resistance, which we attribute to higher microhardness of the surface layer. The coefficient of friction and wear volume of specimens at each different displacement amplitude significantly decreased with increasing milling time. As the displacement amplitude increased, the three fretting states were: partial slip coordinated by elastic deformation; partial slip state coordinated by plastic deformation; and gross slip condition. Our observations indicate that mechanical ball milling could be an efficient approach to improve the fretting wear resistance of GCr15 steel balls.

Characteristics and mechanism of surface damage of hybrid ceramic ball bearings for high-precision machine tool

For investigating surface damage mechanism, three types of hybrid ceramic ball bearings, under the same conditions, were installed and tested in the same spindle of a bearing test bench for comparison. Then the damage characteristic morphologies and microstructure at different operation times were systematically characterized using white-light interferometer, scanning electron microscope, and transmission electron microscope. Meanwhile, the damage mode and related microstructure deterioration around the upper layer of surface have been revealed for these three hybrid ceramic ball bearings. Finally, the results present that the surface fatigue behavior is different from the traditional rolling contact fatigue behavior, since the ceramic ball is almost twice as hard as that of the bearing steel. And a large amount of micropits can been found on the surface of the raceways due to the pressing by hard particles detached from the surface of the ceramic balls. Therefore, this surface damage may result in performance degradation of the precision bearing of the machine tool during industrial ultra-precision machining.

RETRACTED ARTICLE: Application of deep learning to detect defects on the surface of steel balls in an IoT environment

RETRACTED ARTICLE: Application of deep learning to detect defects on the surface of steel balls in an IoT environment

Study on Pitting Fatigue Properties of DLC Coating under Pure Rolling Conditions

To extend the cruising range of electric vehicles (EV), it is necessary to improve the power consumption rate in EV. By rotating the motor at high speed, it is possible to reduce the size and weight, which leads to an improvement in the power consumption rate. However, the fatigue life of the bearings and gears will decrease; therefore, pitting will increase. Diamond-like carbon (DLC) film is expected as one way to prevent the pitting of bearings and gears. DLC has various excellent tribological properties such as low friction and high wear resistance. However, there are few studies to evaluate the pitting resistance of DLC films. In addition, in the contact surface of gears, sliding and rolling contact occur at the same time. Therefore, it is necessary to evaluate the pitting resistance of DLC films at pure rolling condition. In this study, we applied two types of DLC film (ta-C, a-C:H) to the surface of balls. Ball-on-disk tests were conducted under the conditions of lubrication of base oil and pure rolling contact to investigate the effect of these types of DLC film on pitting resistance. We confirmed that the ta-C type DLC film suppresses pitting.

Core-Shell SiO2/Ag Composite Spheres Prepared by Electrical Exploding Wire Plasma Technique: Synthesis and Characterization

Core-shell nanoparticles (SiO2/Ag) were manufactured by using a two-step process: Electric detonation of Ag. Wire in colloidal solution particles then by using laser pulses, nanoparticles are released. The structural features of these nanoparticles were checked by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The (XRD) study showed the progressive coverage of SiO2/Ag by nanoparticles according to the energies of the laser pulse. Measurements of morphology and EDX confirmed the Core/shell structure with particle size at the nano level. It confirmed that preliminary analysis consists of a SiO2 core and an Ag shell from FESEM. The surface of the microscopic balls (SiO2) has been covered completely and homogeneously with Ag nanoparticles, Moreover, Ultraviolet-Visible, and by optical absorption spectroscopy, the Nanoparticles with core crust SiO2/Ag showed excellent photocatalytic activities at various concentrations and laser pulse energy.

A Method for Detecting Metal Surface Cracks Based on Coaxial Resonator

A method based on the resonance frequency shift of coaxial resonator is presented to detect metal surface cracks. Theoretical analysis prove that the resonance frequency shift is always greater than a threshold instead of decreasing as the crack size decreases. Therefore, it can avoid the problem of missing inspection in crack detection. The experiment detects that the threshold of the designed sensor is 2.12 GHz, which is only 3.6% error from the theoretical result. And the designed sensor will produce a frequency shift of 2.16GHz when detecting a 0.2 mm wide crack. Further analysis shows that the sensor can be used to detect tiny cracks on the metal surface with micro-roughness. The width information of the crack can be obtained by scanning, which proves that this method has good potential in the imaging of metal surface cracks. In addition to detecting surface cracks on metal plates, the sensor can also be used to detect the crack on the surface of metal balls.

Preparation of powder coatings on the surface of steel balls by mechanochemical synthesis

This work presents the results of the study of tribological and corrosion properties of powder coatings based on VN, TiN, SiC and Cr2N obtained by mechanochemical synthesis on the surface of steel balls ShKh15. The idea of this method is using the impact energy of moving balls to apply coatings on metal surfaces. Based on the conducted research, it was proved using the method of mechanochemical synthesis possible to obtain a coating of VN, TiN, SiC, and Cr2N on the surface of steel balls. The optimal parameters for coating were chosen: amplitude of the oscillation 3.5 mm; frequency of the oscillation 50 Hz; volume of filling of the chamber 50 %, the diameter of the ball 6 mm; ratio mass of the powder to the mass of the balls mp:mb=1:30, processing time by mechanochemical synthesis is 1 hour. It is established that the change in the characteristics of coatings directly depends on the stiffness and physical and mechanical properties of the source material (substrate) and surface roughness. The results of the tribological study showed that a wear-resistant coating was formed on the surface of the steel balls.

Tribological Investigations of Nano and Micro-sized Graphite Particles as an Additive in Lithium-Based Grease

Graphite is a well-known solid lubricant (SL) additive widely used both as a standalone SL and also as additive in lubricating oils, greases, composites, etc. Size of the additive particles especially nano-particles (NPs) is a major attribute to the performance properties of a composite, oil, grease, etc. This paper highlights the influence of graphite particles of four sizes viz. 50 nm, 450 nm, 4 microns and 10 microns incorporated in the grease in identical amount (4 wt. %) on the anti-friction (AF), anti-wear (AW) and extreme-pressure (EP) performance. The results indicated that all sizes proved beneficial for all the selected properties. Higher the size of particles, lower was the improvement in performance. The particles were most effective as anti-friction additive (AFA) followed by anti-wear additive (AWA) and then extreme-pressure additive (EPA). The NPs exhibited highest improvement as AFA (57%), AWA (41%) and EPA (25%). Raman Spectroscopy proved the formation of exfoliated graphitic layer on the worn surface of balls. Furthermore, SEM micrograph with elemental mapping and XPS spectroscopy analysis proved supportive in comprehending the mechanisms responsible for improved tribo-performance.

Sports balls as potential SARS-CoV-2 transmission vectors

Objects passed from one player to another have not been assessed for their ability to transmit severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We found that the surface of sport balls, notably a football, tennis ball, golf ball, and cricket ball could not harbour inactivated virus when it was swabbed onto the surface, even for 30 ​s. However, when high concentrations of 5000 ​dC/mL and 10,000 ​dC/mL are directly pipetted onto the balls, it could be detected after for short time periods. Sports objects can only harbour inactivated SARS-CoV-2 under specific, directly transferred conditions, but wiping with a dry tissue or moist ‘baby wipe’ or dropping and rolling the balls removes all detectable viral traces. This has helpful implications to sporting events.

Research into biocompatibility and cytotoxicity of daptomycin, gentamicin, vancomycin and teicoplanin antibiotics at common doses added to bone cement.

Objectives This study aims to investigate the biocompatibility and cytotoxicity of daptomycin, gentamicin, vancomycin and teicoplanin at commonly-used dose intervals added to polymethylmethacrylate (PMMA) in vitro.Materials and methods This prospective study was conducted between February 2016 and June 2016. Antibiotics were added to PMMA at doses frequently used in clinical practice. The antibiotic doses added were teicoplanin (2 g, 3 g, 4 g), gentamicin (0.5 g, 0.75 g, 1 g), daptomycin (0.5 g.) and vancomycin (2 g, 3 g, 4 g). Standard cement balls (10 mm) were created. Activated L929 mouse fibroblast cell culture was used for incubation. Agar diffusion, Cell Proliferation Kit II (XTT) test and electron microscope investigations were performed to examine biocompatibility and cytotoxicity.Results In the cytotoxicity test, teicoplanin at 4 g and daptomycin at 0.5 g doses were observed to cause reductions in viability percentages. The same doses caused 20% and 20-40% cell lysis indices during the agar diffusion test. On electron microscope images, cytotoxic effects in fibroblast cells and involvement with the surface of cement balls were observed.ConclusionGentamicin, vancomycin and teicoplanin were observed to be non-toxic and biocompatible at commonly-used dose intervals. Teicoplanin at 4 g and daptomycin at 0.5 g doses were identified to be cytotoxic and not biocompatible. When selecting antibiotics to be added to bone cement, care should be taken that the antibiotic is non-toxic and biocompatible.

Influence of protrusions on the positive switching impulse breakdown voltage of sphere‐plane air gaps in high‐altitude areas

The construction of ultra-high-voltage direct-current power transmission projects in high-altitude areas calls for the research into the discharge characteristics of the air gaps in the valve hall of a power converter station in such areas. Tests on the switching impulse discharge characteristics of the sphere-plane air gap were conducted at Yangbajing test base (Tibet, China) at an altitude of 4300 m on conditions that there were burrs on the 1.3 m diameter shield balls. The discharge characteristics, under the influences of burrs with different lengths and locations, were obtained and compared with test data from low-altitude areas. The results indicate that the arrangements of burrs with different lengths and locations can significantly reduce the switching impulse discharge voltage of sphere-plane air gaps, while the voltage sag gradually decreased down with increasing burr length. Moreover, the larger the sphere-plane air gap is, the smaller the influence of such burrs have. High altitude also substantially decreased the switching impulse discharge voltage of the air gap. When the surface of shield balls was smooth, the U50 saturation of the air gap was more significant than at low altitude; however, if there were burrs on the shield balls, the saturation effect was less significant.