Bearing Steel Ball Research Articles

The effect of air humidity on tribological behaviours of W–C:H coatings with different tungsten contents sliding against bearing steel

Friction and wear behaviors of W–C:H coatings with different tungsten contents sliding against bearing steel balls at different air humidities were investigated. The worn out surfaces of steel balls and coatings were analyzed with the aid of scanning electron microscopy (SEM) and Raman spectroscopy. A tribolayer composed of a graphite-like material mixed with tungsten and iron oxides was observed on the friction surfaces of the steel balls. The chemical and phase compositions of the tribolayer, which depend both on the tungsten content in coatings and air humidity, determine the tribological properties of the W–C:H coating in a frictional contact with bearing steel. At average air humidity (50%), those coatings that contain less than 10at% of tungsten in a frictional contact with steel exhibit favorable tribological properties. The friction coefficient of frictional contacts under test reaches a low value (f∼0.01) at a low air humidity and increases with humidity of up to ca. 0.2. The best tribological properties in a wide range of air humidity (5–90%) have been found for W–C:H coatings with the tungsten content between 2 and 5at%.

Dry sliding wear behaviour of Mg–10Gd–3Y–0.4Zr alloy

In present work, the wear behaviour of a Mg–10Gd–3Y–0.4Zr alloy during dry sliding has been investigated. The experiments were carried out using Ball-on-Flat type wear apparatus against an AISI 52100 type bearing steel ball counterface in a load range of 3–15N, sliding speed range of 0.03–0.24m/s, temperature range of 298–473K and at a constant sliding distance of 400m. Analyses of the wear tracks, worn surfaces and wear debris of the Mg–10Gd–3Y–0.4Zr alloy were carried out using scanning electron microscope. As a comparison, the wear properties of common AC8A aluminium alloy under the same condition also presented. The results indicated that the Mg–10Gd–3Y–0.4Zr alloy exhibited low wear rate compared with cast+T6 AC8A aluminium alloy under the same condition. The wear rate of as-cast Mg–10Gd–3Y–0.4Zr alloy was lower than that of cast+T6 Mg–10Gd–3Y–0.4Zr alloy. The Mg24(Gd, Y)5 eutectic compound of as-cast Mg–10Gd–3Y–0.4Zr alloy could resist the material flow during friction and wear, and affected its wear rate. At high sliding speed, the retained wear debris was the major constituent of producing the severely deformed layers along the sliding direction. The trapped wear debris acted as a protective layer and reduced the wear rate.

Reciprocating Sliding Characteristics of Steel Disc / Bearing Steel Ball in Boundary and Mixed Lubrication

Reciprocating tests were performed to clarify effects of frequency and stroke on friction in boundary and mixed lubrication. With increase in stroke under constant frequency in boundary lubrication, coefficient of friction was observed to increase, which, however, turned to decrease with promotion of oxidation. Specific wear rate varied in accordance with changes in friction. In the next stage, to specify respective effects of frequency and stroke on friction, reciprocating tests were continued by changing frequency and stroke under a constant sliding velocity in boundary and mixed lubrication. There were two regimes of changes in friction in boundary lubrication, depending on whether oxidation was promoted or not. In severe sliding conditions where little oxidation was observed, a combination of higher frequency and smaller stroke produced rougher surfaces, resulting in higher friction. With improved lubricating conditions, however, higher frequency promoted oxidation, lowering friction, whereas in mixed lubrication, a combination of lower frequency and larger stroke contributed to oil film formation, which showed lower friction than that at a combination of higher frequency and smaller stroke.

Study on Wear and Friction Resistance of CrTiAlMoN Coatings Deposited by Magnetron Sputtering

The present research aims to synthesize a nanoscale multilayer CrTiAlMoN hard coating for the modification of wear and friction performance, as compare to CrTiAlN coatings. CrTiAlMoN coatings were deposited on 1045 carbon steel substrates by magnetron sputtering at different Mo target current. The wear and friction resistance were characterized by pin-on-disc test. When a WC-Co ball was used as the counterpart, the coefficients of friction of CrTiAlMoN coatings were found to decrease with the increase of Mo target current, with the lowest value (0.34) being only one half that of CrTiAlN coating (0.76). The combination of high hardness above 36GPa and low coefficients of friction reduces the specific wear rate of the CrTiAlMoN coatings to only 10% of CrTiAlN coatings. When tested against a bearing steel ball, results demonstrate that the effect of Mo on reducing friction of the CrTiAlMoN coatings is not significant and even negative due to adhesive wear.

Performance and tribofilm formation of a low-friction coating incorporating inorganic fullerene like nano-particles

A new tribological coating with potential as a coating for components for low-friction applications is tested and compared to three, state of the art, commercial low-friction PVD coatings. The new coating is an electrodeposited coating composed by a Ni–P matrix incorporating fullerene like nanoparticles of WS 2. The performance of the new coating is compared with three reference coatings in a ball-on-disc setup. The tribological tests involved ball bearing steel balls slid on coated discs, under different conditions of humidity and also with or without oil lubrication. Both mating surfaces were closely investigated in a scanning electron microscope and the low-friction tribofilms formed were further analysed. The correlations found between coefficient of friction, surface roughness of the wear scar, tribofilm formation and contact conditions are discussed. The new coating exhibits a very low coefficient of friction at low humidity, a behaviour closely resembling that of the MoS 2-based commercial reference, whereas the carbon based PVD coatings tested exhibit the reversed dependence of humidity. The low-friction behaviour of the new coating is correlated to the formation of a WS 2 tribofilm with a superficial alignment of the basal planes parallel to the sliding direction. When lubricated with a base oil, the beneficial tribofilm is not formed and the coefficient of friction is much higher. The results show that even though the coating is an electrodeposited coating it can compete with state of the art commercial PVD coatings.

Comparative Study on the Tribological Performance of HFCVD Diamond and DLC Films under Water Lubricating Condition

The tribological performance of conventional microcrystalline diamond (MCD) film and diamond-like carbon (DLC) film is investigated comparatively under water lubricating condition. The MCD and DLC film are deposited on cobalt cemented tungsten carbide (WC-Co) substrate using the hot filament chemical vapor deposition (HFCVD) method and the vacuum arc discharge with a graphite cathode respectively. Scanning electron microscopy (SEM), white light interferometer, and Raman spectra are employed to characterize as-deposited MCD and DLC samples. The friction tests are carried out on a ball-on-plate reciprocating friction tester, where the sliding process is conducted under water lubricating condition. Silicon nitride, tungsten carbide, ball-bearing steel and copper are used as counterpart materials. The results indicate that DLC film always exhibits lower friction coefficient than MCD film under water lubricating condition, except the case of sliding against the silicon nitride, in which DLC film is worn out very rapidly and thus leads to the high friction coefficient. The wear resistance of DLC film under water lubricating condition is significantly poorer than that of MCD film. While sliding against silicon nitride, tungsten carbide, ball-bearing steel and copper, its wear rate is calculated as 3.67´10-7mm3N-1m-1, 9.31´10-9mm3N-1m-1, 3.54´10-7mm3N-1m-1, and 4.97´10-8mm3N-1m-1respectively. Comparatively, no measurable wear track can be found on the worn surface of MCD films.

On the influence from micro topography of PVD coatings on friction behaviour, material transfer and tribofilm formation

Abstract PVD coatings based on amorphous carbon with metal-carbides are currently gaining a high interest for use on machine elements due to their potential to give low friction and low wear of the counter surface. However, the performance varies significantly between the various types of such coatings and the causes of this are not clear. One factor is the micro topography of the coating surface. This topography may influence the friction in many ways; by changing the state of lubrication, by causing scratching of the counter surface, by modifying the topography of the counter surface the material transfer, the tribofilm formation, etc. TaC/a-C coatings, produced by co-sputtering of carbon and tantalum in an argon atmosphere, were deposited on high speed steel substrates exposed to varying degrees of etching to produce a range of surface roughnesses. Ball-on-disc experiments were used to evaluate the tribological properties of the coatings in dry condition against a ball bearing steel ball. The surfaces were analysed using various advanced techniques, including, SEM, XPS, Raman, EDS and AFM, all both prior to and after the testing. It was shown that the resulting surface topography of the coating is affected even by very small protrusions on the substrate. The coefficient of friction decreased during use to a stable level, due to a complex process including tribofilm build-up on the sliding ball. Surfaces with lower protrusions exhibited a faster friction decrease, i.e. a faster running in.

The influence of porosity and hot isostatic pressing treatment on wear characteristics of cast and P/M aluminum alloys

Abstract Porosity is a common feature of cast and sintered aluminum alloys and strongly influences their properties and applications. Al–Si alloys are widely used in a variety of automotive components due to their excellent strength to weight ratio. Porosity adversely affects the mechanical properties and wear resistance of these components. In the present investigation, dry sliding wear behavior was investigated in the load range 6–20 N against AISI 52100 bearing steel ball using a reciprocating ball-on-flat configuration at a frequency range of 4–20 Hz for cast and 15 Hz for sintered samples. It is found that, wear within the present load and frequency ranges is due to plastic deformation and delamination. It was also found that hot isostatic pressing treatment (HIP) decreases the total amount of porosity and average pore size, but at the expense of reduced hardness. The competition between the beneficial effect of lower porosity and the detrimental effect of lower hardness determines the final wear rate.

Friction and wear properties of in situ (TiB2+TiC)/Ti3SiC2 composites

Abstract The non-lubricated, ball-on-flat sliding friction and wear properties of in situ (TiB2 + TiC)/Ti3SiC2 composites against bearing steel ball were investigated. The load was varied from 10 to 30 N. The material without TiB2 shows an increasing friction coefficient with the increasing load. However, for (TiB2 + TiC)/Ti3SiC2 composites, the friction coefficient shows an insensitivity to load. Both friction coefficient and wear rate initially increase and then dramatically decrease with TiB2 content increasing from 0 to 20 vol%. (TiB2 + TiC)/Ti3SiC2 composites with 15 vol% and 20 vol% TiB2 show excellent wear resistance, whose friction coefficient and wear rate are much lower than those of TiC/Ti3SiC2 composite. The enhanced wear resistance is mainly attributed to the facts that the hard TiB2 and TiC particles nail the surrounding soft matrix and decentralize the shear stresses under the sliding ball, a self-lubricating oxide debris forms on the wear surface, and the wear mode converts from adhesive wear to abrasive wear.

The Influence of Plasma Nitriding Pre-Treatment on Tribological Properties of TiN Coatings Deposited by PACVD

The aim of this study is to investigate the effect of plasma nitriding pre-treatment (PN) on mechanical and tribological behavior of TiN coatings produced by plasma-assisted chemical vapor deposition (PACVD). The heat treatment of quench and temper was carried out on hot work AISI H11 (DIN 1.2343) steel samples. A group of samples were plasma nitrided at 500 °C for 4 h in an atmosphere containing 25 vol.% nitrogen and 75 vol.% hydrogen. Then TiN layer was deposited on all of samples at 520 °C temperature, 8 kHz frequency, and 33% duty cycle. The microstructural, mechanical, and tribological properties of the coatings were investigated using SEM, WDS, AFM, microhardness tester, and pin-on-disc wear test. The load of wear test was 10 N and the samples were worn against different pins, ball-bearing steel (DIN 1.3505), and cemented tungsten carbide (WC-Co). The results indicate that the difference of hardness between the samples with PN-TiNlayer and those samples with only TiN layer without PN was 450 HV and the former samples showed a significant amount of wear resistance in comparison to the latter ones.

An investigation of palliation of fretting wear in gross slip regime with grease lubrication

PurposeThe paper aims to study comparatively the fretting behavior in gross slip regime of fretting both under grease lubrication and dry condition and to investigate the mechanism of palliation of fretting wear with grease lubrication.Design/methodology/approachAll fretting tests were carried out on high‐temperature fretting devices with standard GCr15 bearing steel ball against 45 steel flat and against GCr15 bearing steel flat contact pairs. The wear scar was examined by optical microscope, surface profiler and the confocal laser scanning microscope as well as energy dispersive X‐ray spectroscopy.FindingsCompared with dry condition, the coefficient of friction and wear are decreased drastically and wear occurs mainly at the early stage of fretting under grease lubrication. The palliation effect of grease lubrication is closely associated with the amount of oil separated from the grease, the low‐oxidation corrosion and high‐hardness white layer. However, the bubbles which expelled from the contact edges have little influence on fretting wear.Research limitations/implicationsThe tested greases do not contain any additives for preventing possible misinterpretations of the results, but it is necessary to investigate the influence of different lubricant additives added to grease on friction and wear at different fretting conditions.Practical implicationsThe research reveals that the palliation effect of grease lubrication on fretting wear is related closely to the amount of oil separated from the grease. The bigger penetration and more susceptible greases, which are easier to separate from the base oil, should be taken into account for palliation of fretting wear.Originality/valueThe presented results help to understand the palliation mechanism of grease lubrication and could be useful for designers of engineering assembly for which fretting wear is an issue.

Research on Grinding Technology Optimization of Bearing Steel Ball

The paper studied on the balling-up mechanism of hard-grinding by focusing on the defects in the process of the hard-grinding of steel ball. In order to achieve better precision and efficiency in the process of producing steel ball, we improves the grinding wheel’s structure by increasing the rotation velocity of the ball and thereby improving the producing efficiency.

High Pressure Water-Jet Technology for the Surface Treatment of Al-Si Alloys and Repercussion on Tribological Properties

Recent developments in high pressure water-jet technology have brought the process to the forefront as a means of surface treatment. Water jet technology offers cleaning, cutting, processing as well as potential refinement of surface properties. By adapting the process parameters the surface characteristics can be changed while the profile remains the same. In the present study, water-jet technology was used for the surface treatment of Al-Si alloy to investigate its effect on tribological properties. Dry sliding wear behavior was investigated against AISI 52100 bearing steel ball using a reciprocating ball-on-flat configuration. Optical microscopy examination reveals that ploughing of grains, transgranular and intergranular propagation of cracks; are the mechanisms by which material is removed during water jet treatment. While, on the other hand, SEM observation of the wear track reveals that plastic deformation and delamination are the dominant wear mechanism during the wear process. Water jet treatment was compared to hot isostatic pressing in terms of its effects on wear resistance and surface porosity of Al-Si alloy. It was found that, hot isostatic pressing reduces the total amount of porosity at the expanse of hardness while water jet treatment produces a compressed surface having higher hardness and compressive residual stress, which ultimately increases wear resistance.

Effect of porosity on dry sliding wear of Al–Si alloys

Porosity adversely affects the pressure tightness (ability of a system to hold pressure), mechanical properties and wear resistance of components. The amount of porosity and the size and shape of pores have a great impact on material removal during wear. Al–Si alloy with different porosity levels was prepared using powder metallurgy technique. Dry sliding wear behavior was investigated against AISI 52100 bearing steel ball. It was found that the wear rate gradually rises with surface porosity, then drops as porosity and pore size reach critical levels. A model was developed to explain the relationship between porosity and pore size.

Friction and contact resistance of nanocomposite Ti–Ni–C coatings

Ceramic nanocomposite coatings in the Ti–Ni–C were deposited using PVD and studied with respect to tribological properties and contact resistance. It was shown that coatings could be deposited combining of a low contact resistance and a low friction coefficient against silver, making them suitable for use in high performance electrical contacts. Nine coatings with different amounts of C and Ni were deposited. Coatings on flat Ni plated copper substrates were tested in a tribological ball-on-disc setup against ball bearing steel balls. Depending on primarily the amount of carbon the coatings showed very different friction coefficient and wear rate. The coatings were also deposited on cylindrical Ni plated copper substrates. Using geometrically identical silver plated cylinders as counter surface these were evaluated in a test setup better resembling a real life electrical contact. For most coatings a low electrical contact resistance was measured. The evolution of friction coefficient and contact resistance was correlated to wear marks and contact tracks, with their generated tribofilms, as examined after testing using electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy.

Study on the Friction Behavior of HFCVD Diamond Films on Silicon Nitride Substrates

The friction behaviors of CVD diamond films on silicon nitride substrates are investigated comparing with the uncoated silicon nitride samples. Two types of CVD diamond films, namely MCD and NCD films, are deposited on the silicon nitride substrates using HFCVD method, and then SEM, while light interferometer, XRD and Raman spectra are employed to characterize as-deposited diamond films. The friction tests are carried out in a ball-on-plate reciprocating friction tester, with ball-bearing steel, copper, tungsten carbide and tungsten carbide as the counterpart materials. The results show that the diamond film deposited on silicon nitride substrate has significant effect on reducing the friction coefficient and enhancing the wear resistance. The friction coefficients of MCD and NCD films are around ~0.35 in dry sliding against ball-bearing steel and copper, while for sliding with the tungsten carbide and silicon nitride, the friction coefficients of NCD films even decrease as low as ~0.12 and ~0.08 respectively. The special wear rate of the silicon nitride and NCD film can be estimated as 6.2167×10-5 mm3 N-1 m-1 and 4.03×10-7 mm3 N-1 m-1 with the counterface of silicon nitride. Comparatively, no measurable wear occurs on the worn surface of the MCD film.

Friction and cutting properties of hot-filament chemical vapor deposition micro- and fine-grained diamond coated silicon nitride inserts

The micro-crystalline diamond (MCD) and fine-grained diamond (FGD) films are deposited on commercial silicon nitride inserts by the hot-filament chemical vapor deposition (HFCVD) method. The friction and cutting properties of as-deposited MCD and FGD films coated silicon nitride (Si3N4) inserts are comparatively investigated in this study. The scanning electron microscopy (SEM) and Raman spectroscopy are adopted to study the characterization of the deposited diamond films. The friction tests are conducted on a ball-on-plate type reciprocating friction tester in ambient air using Co-cemented tungsten carbide (WC-Co), Si3N4 and ball-bearing steel (BBS) balls as the mating materials of the diamond films. For sliding against WC-Co, Si3N4 and BBS, the FGD film presents lower friction coefficients than the MCD film. However, after sliding against Si3N4, the FGD film is subject to more severe wear than the MCD film. The cutting performance of as-deposited MCD and FGD coated Si3N4 inserts is examined in dry turning glass fiber reinforced plastics (GFRP) composite materials, comparing with the uncoated Si3N4 insert. The results indicate that the lifetime of Si3N4 inserts can be prolonged by depositing the MCD or FGD film on them and the FGD coated insert shows longer cutting lifetime than the MCD coated one.

Influence of Surface Roughness on the Transfer Film Formation and Frictional Behavior of TiC/a-C Nanocomposite Coatings

Influence of surface roughness on the friction of TiC/a-C nanocomposite coatings while sliding against bearing steel balls in humid air was examined by detailed analyses of the wear surfaces and the wear scar on the ball counterparts by atomic force microscopy, optical, and confocal microscopy. It was observed that the surface roughness of the coatings essentially determines the wear behavior of the ball counterpart, which consequently influences the transfer film formation. A rough coating causes abrasive wear of the steel ball during the running-in period, which impedes the formation of a stable transfer film and leads to higher values of coefficient of friction (CoF). Moreover, the CoF does not show a decreasing trend after the running-in period, although the roughness of the coating was greatly reduced. Replacing the worn ball with a new one after the running-in period yields lower CoF values similar to that observed for a smooth coating. In both of the cases, no wear of the steel ball occurs and a stable transfer film forms and effectively covers the contact area. The influence of the wear debris on the formation of the transfer film is also discussed.

Modify the friction between steel ball and PDMS disk under water lubrication by surface texturing

Surface texture has been recognized as an effective means of surface engineering to improve the tribological properties of sliding surfaces. Various lubrication mechanisms of surface texture have been studied for the surfaces of metals and ceramics. In order to investigate the effects of surface texture for soft material, the patterns of micro-dimple with different dimple diameters and area ratios were fabricated on a polymer material poly(dimethylsiloxane) (PDMS) by lithography & replica techniques. A preliminary study on the friction of the polymer disk sliding against a bearing steel ball under water lubrication was carried out. The effects of surface texture on the friction of polymer material were evaluated. It is found that surface texture is capable of reducing friction at low sliding speed, as well as increasing friction at high sliding speed condition.

Friction and Wear of Polyamide 66 Composites Filled with RB Ceramics Particles under Dry Condition

This study investigated the effect of a particle diameter and a weight fraction of RB ceramics particles on friction and wear of polyamide 66 composites filled with RB ceramics particles (PA66/RB ceramics composites) sliding against a bearing steel ball under dry condition. RB ceramics particles with a mean diameter of 3, 30, and 150 μm were used as the filler. Weight fractions of RB ceramics particles were 10, 30, and 50 mass% for the mean diameter of the particles of 3 μm, and 30, 50, and 70 mass% for the mean diameters of 30 and 150 μm. The smaller mean diameter and the higher weight fraction of RB ceramics particles provided lower friction coefficients and lower specific wear rates with the PA66/RB ceramics composites. The composite with a mean diameter and a weight fraction of RB ceramics particles of 30 μm and 70 mass% took the lowest friction coefficient of 0.27 among the composites. The composite with a mean diameter and a weight fraction of RB ceramics particles of 3 μm and 50 mass% took the lowest specific wear rate of 1.3 × 10-9mm2/N among the composites, which was equivalent to the specific wear rate of RB ceramics disk.