Bearing Steel Ball Research Articles

Ball-on-Disk Wear Maps for Bearing Steel–Hard Anodized EN AW-6082 Aluminum Alloy Tribocouple in Dry Sliding Conditions

In recent years, Golden Hard Anodizing (G.H.A.®) has been developed as a variant of the traditional hard anodizing process with the addition of Ag+ ions in the nanoporous structure. The tribological properties of this innovative surface treatment are still not well understood. In this study, ball-on-disk tests were conducted in dry sliding conditions using 100Cr6 (AISI 52100) bearing steel balls as a counterbody and GHA®-anodized EN AW-6082 aluminum alloy disks. The novelty of this work lies in the mapping of the wear properties of the tribocouple under different test conditions for a better comparison of the results. Three different normal loads (equal to 5, 10, and 15 N) and three different reciprocating frequencies (equal to 2, 3, and 4 Hz) were selected to investigate a spectrum of operating conditions for polished and unpolished G.H.A.®-anodized EN AW-6082 aluminum alloy. Quantitative wear maps were built based on the resulting wear rate values to define the critical operating limits of the considered tribocouple. The results suggest that the coefficient of friction (COF) was independent of test conditions, while different wear maps were found for polished and non-polished surfaces. Polishing before anodizing permitted the acquisition of lower wear for the anodized disks and the steel balls.

On mechanical and tribological behaviour of microwave sintered TiN – 5 wt% Al2O3–5 wt% Y2O3 nanocomposite

Titanium nitride has potential applications in wide range of mechanical parts, cutting tools etc., primarily due to its high wear resistance. In the present study, a novel TiN-based nanocomposite was developed with nano additives alumina (Al2O3) and (Y2O3), 5 wt% each; using microwave irradiation at 900 W in ambient atmosphere. In-situ microwave sintering was carried out at a temperature of 1500 °C and 5 min holding time. The sintered nanocomposites achieved a relative density of ∼93%. XRD analyses showed that the major TiN phase was retained without any significant change in its peak positions after sintering. Minor phases of Y2Ti2O7 and Y3Al5O12 were formed during sintering due to chemical realignment of the constituent phases, were detected which acted as crack inhibitors. Microstructural studies indicated homogeneous distribution of the additives throughout the TiN matrix. The average Vickers microhardness of the TiN nanocomposites was ∼14 GPa, while indentation crack resistance was estimated within 3.9–4.0 MPa·m1/2. Wear and friction studies (ball-on-disc) of the microwave sintered TiN nanocomposite carried out with bearing steel ball under dry (unlubricated) and under deionised water (lubricated) sliding exhibited promising tribological behaviour. The friction coefficient (COF) between the contact pair was monitored within 0.5–0.6 after 45 min of dry sliding. Wear volume of the nanocomposite was obtained between 0.013 and 0.058 mm3 after 45 min of sliding (dry). Presence of iron oxides on worn surfaces confirmed mass transfer from the steel counterbody to the nanocomposite surface. Analyses of the worn surfaces showed that the wear mechanisms were predominantly abrasive and adhesive.

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.

THE INFLUENCE OF THE CARBURIZING PROCESS ON THE IMPACT-SLIDING WEAR BEHAVIOR OF 14NiCr14 STEEL

Weapons depend largely on the barrel. Gunpowder combustion converts chemical energy into thermal and mechanical energy. Barrels give projectiles initial speed and flight direction, and helical grooves require fast spinning for stability while moving toward the target. Due of barrel exposure to heat, high pressures, gunpowder vapors, and external impacts, this weapon element needs extensive investigation. The study discusses carburizing for surface modification in high-pressure circumstances to improve gun barrel interior line tribology. Carburizing has been detected at a depth of 960 μm from the surface, as revealed by light-optical microscope images. The microhardness test has been performed on the sample's cross section, which has a maximal hardness of 650 ± 10 HV0.05 close to the surface and 250 ± 5 HV0.05 close to the interface. At room temperature (RT), this study looked at how the carburizing process affects the impact-sliding wear performance of 14NiCr14 steel, which is widely used in the barrel extensions of guns under complex loading conditions. A series of impact-sliding wear experiments were conducted on 10 mm-diameter bearing steel balls made of 52100-grade steel, for a total of 4297 loading cycles. A 2-D contact profilometer and a light optical microscope (LOM) then examined the wear tracks that had formed on the samples. The carburized steel caused a decrease in the wear rate at the impact and sliding zones of the wear track.

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.

The influence from PTFE on surface and sub-surface damages of glass fiber reinforced PPS

Polymer composites are common materials for tribological components, even at relatively high operating temperatures. One advantage is the possibility to add low friction additives, such as PTFE, to the base material. In this paper the influence of such additives was studied, with focus on surface and sub-surface damages. The polymer composites were PPS with glass fibers (PPS-F), PPS with glass fibers and PTFE (PPS-L) and PEEK with carbon fibers, graphite and PTFE (PEEK-L). A reciprocating ball-on-disc test set-up, with ball bearing steel balls as counter material, was used with 5 N and 15 N normal load. The tests were run for 2,000 and 10,000 cycles in room temperature, 80 °C and 120 °C. PPS-F showed high friction (µ ≈ 0.4–0.5) and severe surface damage of both the polymer and the counter surface. Sub-surface cracks, detachment of fibers from the polymer and a deformed surface layer was revealed, when studied in cross section. The load and temperature had negligible effect on the friction, however a higher temperature resulted in more surface damage of the PPS-F. PPS-L and PEEK-L showed relatively low friction (µ ≈ 0.1) and superficial surface damage. XPS analysis revealed a thin tribofilm of PTFE in the wear track for PPS-L.

Numerical and experimental study for process improvement of cross-wedge rolling of bearing steel balls

The uniaxial compression experiments were conducted on GCr15 bearing steel to obtain the flow stress curves under hot deformation conditions. Based on the results of uniaxial compression experiments, finite element modeling was conducted on the cross wedge rolling (CWR) of GCr15 bearing steel balls, and numerical simulation was conducted using Simufact Forming 16.0. The results show that the distribution of effective strain of existing CWR steel balls is uneven, which may lead to uneven quality of steel balls. In addition, the three principal stresses at the center of the steel balls are all tensile stresses, and the effective stress at the center of the middle ball is relatively large, which can easily induce central defects. Moreover, different diameter billets were used for steel balls rolling experiments. It can be seen that when the die cavity is underfilled with billet, the rolled steel balls have no central defects. When the die cavity is fulfilled with billet, there is central piercing appearing at the middle ball, while the side balls have no obvious central defects. Finally, the paper proposes the method of even numbered ball rolling (ENBR) which starts from the middle connector to improve the CWR process of steel balls.

Improving the wear resistance of 440 C bearing steel balls through mechanical ball milling induced gradient structure

This study explored 440 C steel ball wear resistance via mechanical ball milling with Al2O3 powder. We used a customized grinding jar to compare heat-treated, untreated, Al2O3-treated, and Al2O3 + distilled water-treated samples. We assessed wear resistance, residual stress, microhardness, and surface roughness. Results revealed that the combination of distilled water and Al2O3 powder induced nanostructured stacking faults, increased dislocation density, and grain refinement. Treated samples had a > 200 µm thick strengthened layer, − 355 MPa residual stress, and max microhardness of 776.6 HV. These samples showed superior wear resistance, reduced wear volume, and lower friction. This suggests that Al2O3 powder and distilled water in mechanical ball milling enhance ball mechanical part wear resistance, offering industrial potential.

Influence of MoS2 coating treatment on the damage behaviour of the self-lubricating friction pair of spherical plain bearings

This study applied a MoS2 coating layer on the surface of 100Cr6 bearing steel balls through high-temperature sintering and tested and evaluated the modified friction pair. Compared to the unmodified friction pair, the MoS2 coating treatment significantly improved the self-lubricating property of the friction pair, reduced the friction coefficient of the friction pair by 0.05, maximum wear depth was reduced by 32% during the test cycle and prolonged the retention time of the PTFE transfer film at the friction interface. After modification, the wear mechanism of the friction pair changed from abrasive wear to fatigue wear and then to slight adhesive wear. Results indicate that MoS2 coating has great application prospects in improving the tribological properties and operational reliability of spherical plain bearings.

Operando tribo-Raman spectroscopic observation for wear processes of superlow frictional concentrated polymer brushes at frictional interface

Concentrated polymer brushes (CPBs) synthesized by advanced surface-initiated controlled radical polymerization have received increasing attention in the tribological field because CPBs in good solvents exhibit superlow friction phenomena under macroscopic severe sliding conditions. To realize tribological applications of CPBs, an understanding of the wear mechanisms of CPBs is required to develop a method to enhance their durability. In this study, an operando tribo-Raman spectroscopic experiment, which is an effective approach for revealing the wear mechanisms of tribo-materials, was conducted on the frictional interface between a polymethyl methacrylate (PMMA)-CPB and a bearing steel ball immersed in an ionic liquid (IL), which is a good solvent for PMMA-CPBs. From the operando tribo-Raman results, the concentrations and molecular structures of the PMMA-CPBs and IL at the frictional interface were found to be constantly changing with the sliding cycles during operation. Moreover, their time-dependent changes strongly affected the wear process and superlow friction phenomena of the PMMA-CPB lubricated with the IL. Consequently, our results suggest that controlling the degree of swelling of CPBs at frictional interface is an effective approach for realizing a durable-superlow frictional tribo-system of CPBs.

Tribological Behavior of Cathode Plasma Electrolytic Deposited Al2Y4O9 Coating on Aluminum Alloy

Ceramic coatings are widely used as protective barriers on the surfaces of various metals and alloys. Herein, a novel surface ceramic treatment, i.e., cathode plasma electrolytic deposition (CPED), is proposed for the surface of an Aluminum (Al) alloy. The coating, prepared in an Y(NO3)3 aqueous solution on the surface of the Al alloy, consists of Al2Y4O9 as the major phase component, Y2O3 as a minor phase component, and amorphous Al2O3 in the grain boundaries. As the applied voltage and deposition time increased, the crystallization of the coatings was enhanced. When deposited at 130 V for 10 min, the contact angle of the ceramic coating reached 141.0° ± 2.6°, indicating an enhanced self-cleaning effect. The ceramic coating also exhibited excellent self-lubricating and anti-wear effects. The friction coefficient of the CPED-treated sample vs. ZrO2 ball or bearing steel ball decreased from 0.55–0.65 to 0.26–0.31 when the load was 3 N and the reciprocating velocity was 10 mm/s. Correspondingly, the wear rate of the CPED-treated sample vs. the ZrO2 ball or bearing steel ball was significantly reduced. Results indicated that CPED is effective for the formation of self-cleaning and anti-wear ceramic coatings on Al alloys.

Further Investigations and Parametric Analysis of Microstructural Alterations under Rolling Contact Fatigue.

Bearing elements under rolling contact fatigue (RCF) exhibit microstructural features, known as white etching bands (WEBs) and dark etching regions (DERs). The formation mechanism of these microstructural features has been questionable and therefore warranted this study to gain further understanding. Current research describes mechanistic investigations of standard AISI 52100 bearing steel balls subjected to RCF testing under tempering conditions. Subsurface analyses of RCF-tested samples at tempering conditions have indicated that the microstructural alterations are progressed with subsurface yielding and primarily dominated by thermal tempering. Furthermore, bearing balls are subjected to static load tests in order to evaluate the effect of lattice deformation. It is suggested from the comparative analyses that a complete rolling sequence with non-proportional stress history is essential for the initiation and progression of WEBs, supported by the combination of carbon flux, assisted by dislocation and thermally activated carbon diffusion. These novel findings will lead to developing a contemporary and new-fangled prognostic model applied to microstructural alterations.

Friction-Induced Clustered Rearrangement at a PbS Quantum Dot Nanocoating via Long-Term Lubrication under an Atmosphere Environment.

We report a long-term lubrication for a PbS QD nanocoating sliding against bearing steel balls in the air. Through tribo-physchemical interactions, ultralow friction (μ ≈ 0.078 ± 0.0026) is achieved for the system tested under 1 N for 60 min. During the rubbing process, the tribo-film of the counterfacing ball is covered by a degraded PbS QD layer and amorphous mixed phase. Meanwhile, the disc track surface is composed of degraded PbS QD layers, clustered rearranged PbS QD districts, induced decomposed Pb-enriched multilayers, and an amorphous mixed phase via friction-induced structural transformation. The PbS QDs are transferred onto the sliding contacts to form a robust tribo-film, which is the key to realizing ultralow friction. Consequently, a long-term lubrication mechanism is attributed to the synergetic tribo-physchemical interaction along sliding interfaces upon shift, redirection, and decomposition of nanoparticles. These discoveries reveal QD-based nanolubricants in common working conditions for mechanical engineering.

Transitional behavior in sliding wear of martensitic layer obtained with SHPTN process on AISI 409 steel

Samples of AISI 409 were thermochemically treated by the Solution Heat Treatment after Plasma Nitriding (SHTPN) process. SHTPN process consisted of a nitriding step followed by solution annealing at 1100 °C and rapid cooling down to room temperature. The second cycle of quenching (950 or 1050 °C), followed by tempering (250, 450, or 650 °C), was performed sequentially to SHTPN. Lubricated reciprocating tests were employed to analyze friction and wear behaviors. A bearing steel ball was used as a counterpart. The analysis of worn surfaces was assessed using optical interferometry and depth-sensing indentation. The last technique allows determining the work hardening caused by the wear process. Friction behavior was related to the deformation component: the higher the hardening, the higher the friction coefficient. Abrasion is the primary mechanism observed in all specimens, but there is a transitional behavior that depends on the original hardness of the surface. Samples with a similar hardness of bearing ball presented delaminated regions caused by highly deformed thin layer fatigue. Amongst SHTPN conditions NS-Q950-T2 and NS-Q1050-T2 presented the best balance of wear and corrosion performances.

In Situ‐Formed Ultralow Wear Tribofilms Induced by Poly(Acrylic Acid)‐co‐MXene‐Modified Polymer‐Like Carbon Films

Herein, two types of tribocouple pairs based on polymer‐like carbon (PLC) films are designed through the in situ‐formed MXene coating. The in situ‐formed MXene coatings are synthesized via the in situ organic–inorganic chemical composite technique‐induced anionic polymers with different molecular weights (≈450 000 and ≈4 000 000, respectively). Next, the tribotesting condition is controlled in the ambient environment under different loads by bare and PLC‐coated bearing steel balls as counterbodies. During the whole sliding process, a lubricity state (friction coefficient is about 0.21 and wear rate is about 1.5 × 10−6 mm3 N−1 m−1) is realized on the self‐mated PLC system. Meanwhile, the contact surfaces are covered by graphitic 2D Ti3C2. Compared with the high‐molecular‐weight modifier system, most poly(acrylic acid)‐co‐MXenes grafted by the low‐molecular‐weight poly(acrylic acid) form far more sp 2‐C phases. Moreover, active groups are potentially involved in forming a tribofilm, which enhances the overall lubricity of MXenes during sliding. This verifies the key to achieving low friction and ultralow wear based on the formation of the nanostructured sliding interface upon MXenes and provides an expanded application of solid lubricants.

Surface degradation of nitrided hot work tool steels under repeated impact-sliding contacts: Effect of compound layer

Wear behaviour of quenched and tempered (QT) hot work tool steels (Uddeholm QRO90) was investigated against SAE 52100 grade bearing steel balls after gas nitriding using a dedicated laboratory scale impact-sliding wear test rig. Gas nitriding was employed in a fluidised bed reactor under two alternative regimes: i. “High Temperature Nitriding (HTN)” carried out at 510 °C and ii. “Low Temperature Nitriding (LTN)” carried out at ≤ 400 °C. The HTN process resulted in the formation of ∼2 μm thick external compound layer, whereas the LTN processed steels were free of any surface compound layer formation. After the impact-sliding wear tests employed at room temperature (RT), the prevailing wear mechanisms of the examined steels were assessed as tribo-oxidation and fatigue wear. The testing at 600 °C induced different wear mechanisms for the HTN and the LTN steels. While tribo-oxidation and fatigue wear were preserved for the HTN steel, plastic deformation dominated the wear that progressed on the compound layer free surface of the LTN steel. Impact-sliding wear testing at 600 °C showed that the wear rate of LTN > HTN steels, as opposed to the wear rate at RT where wear rate of HTN > LTN.

Effect of beryllium-containing steel VNS32-VI structure on hardness and characteristics of dry sliding friction in tribocontact with ball-bearing steel ShKh15-ShD

The study of the microstructure, hardness and tribological characteristics of beryllium-containing steel VNS32-VI depending on the quenching temperature has been carried out. According to the results of metallographic studies, it was found that with an increase in the hardening temperature, the amount of excess and intermetallic phases decreases. An increase in the hardening temperature after 950 °С leads to a decrease in hardness and an increase in wear resistance. The VNS32-VI steel with the lowest hardness has the best tribological characteristics.

Micromechanical and Tribological Properties of Nanostructured Carbonitride Coatings Deposited by PVD Technique

Nanostructured smart coatings (NSC) based on the TiAlSi-CN composite structure elements were deposited using reactive high-power physical vapor deposition (PVD) technique. The advanced modular deposition system included up to 8 high-power magnetron sputtering devices (MSD) allowing operate them simultaneously and exceed power density of 120 W/cm2 within each device erosion zone. The novel designed NSC on bearing steel 100Cr6 substrates demonstrated enhanced mechanical and tribological properties comparably with bearing steel ones required for multifunctional high-tech applications. The deposited NSC containing TiAlSi-CN nanoparticles strengthened by elemental additives Cr and Nb exhibited microhardness as high as 2500 HV values in comparison with 750 HV of 100Cr6 steel substrates. Load-displacement curves obey Meyer’s power-law surprisingly well because power-trendline fitted ones by R-squared value of 0.9999 for all the film-samples. Tribological properties were measured under dry friction conditions between the bearing steel ball of Ø 6 mm and the film-samples’ flat surface. Coefficient of friction (CoF) ranges between 0.22-0.56 depending on a sample and load. Tribotracks worn under the friction indenter were too shallow to evaluate them by Mitutoyo profilometer SJ-500. Therefore, the wear rate was estimated as ball wear of the friction indenter.

Tribolayer‐dependent origin of ultralow friction in nanocrystalline diamond films sliding against Si3N4 ball

This study investigates the role of sliding counterbodies, which significantly affect the wear properties and friction of nanocrystalline diamond (NCD) film. The bearing steel balls exhibit a high friction coefficient of 0.12, whereas a ceramic ball of Si3N4 achieves an ultralow friction coefficient of 0.06. The evolution of different friction coefficients with different counterbodies is associated with the formation of a tribolayer at the sliding interface. The decreased friction coefficient in NCD films sliding against Si3N4 ball is likely linked to the occurrence of lubricating nanostructures, especially the silica‐like oxide compounds and graphite‐like carbon phases. The findings of this study may provide new avenues for the design and development of wear‐resistant and environment‐friendly hard carbon films.

Non-contact monitoring and evaluation of subsurface white etching area (WEA) formation in bearing steel using Rayleigh surface waves

The extreme dynamic loading on bearings during transient operating conditions in wind turbine gearbox instigates white etching area (WEA) formation and abrupt premature cracking. Thus there is much interest in developing an appropriate condition monitoring system to predict premature bearing failures instead of destructive microstructure analysis. Recently, guided ultrasonic waves have been extensively used for health monitoring of engineering components. This feasibility study aims to detect subsurface WEA formation using ultrasonic surface (Rayleigh) waves. WEA is replicated from impact loading experiments at 2 GPa contact pressure, with loading frequency 4.5 Hz on AISI 52100 bearing steel balls by varying test durations. Rayleigh wave signatures of the ball were analysed before and after experiments to recognize microstructural changes and confirmed using destructive microstructural analyses.