Rolling Contact Fatigue Evaluation of Advanced Bearing Steels with and Without the Oil Anti-Wear Additive Tricresyl Phosphate

The effect of the oil anti-wear additive tricresyl phosphate (TCP) on rolling contact fatigue (RCF) life of advanced bearing steels—AISI VIMVAR M50, CSS 42L, Pyrowear 675, and Cronidur 30 was investigated with silicon nitride balls at 177 °C and at a maximum Hertzian stress of 5.5 GPa. TCP at 1% additive concentration was blended into a synthetic polyol ester turbine engine lubricant basestock having a nominal viscosity of 3 cSt at 100 °C. Additionally, the basestock was fortified with the anti-oxidants dioctyl-diphenyl amine (DODPA) and phenyl-α-napthyl amine (PANA) at 1% concentration each. The presence of TCP has a measurable positive effect on RCF life and wear. Also, all the advanced bearing materials exhibited superior fatigue life compared to conventional bearing steel M50, both with and without TCP. The study indicates that current gas turbine lubricant formulations with TCP have positive effects on fatigue life and wear performance of M50, Pyrowear 675, CSS 42L, and Cronidur 30.     

An Approach to Evaluate the Abrasive Land Wear of High-Speed Bearings

State-of-the-art bearing materials, such as Pyrowear 675(P675) have been developed to meet the requirements of the next generation of gas turbine engines. P675 bearings have exhibited higher land wear compared to conventional M50 bearings under contaminated test conditions. Surface modification techniques can be applied to enhance the wear resistance of bearing land surfaces. A coating has been developed to minimize abrasive wear of land surfaces. A new procedure using a 40 mm bearing test rig has been developed to effectively evaluate land wear under simulated contaminated condition. Test conditions including contamination concentration, test duration, test temperature and lubricant flow rate were optimized to obtain measureable wear on the land surfaces in a reasonable test time. Results obtained using M50 Nil, P675 and M50 bearings are presented to illustrate the viability of the test procedure.     

Sliding wear behaviour of some Fe-, Co- and Ni-based metallic glasses during rubbing against bearing steel

The sliding wear behaviour of several compositions of Fe-, Co- and Ni-based metallic glasses have been studied while rubbing against AISI 52100 bearing steel under reciprocating-sliding conditions. The wear resistances of Fe-based metallic glasses and Ni-based metallic glass (MBF 50) have been found to be superior to that of the mating AISI 52100 bearing steel. The examination of worn surfaces indicates that the superior wear resistance of metallic glasses is not merely owing to their high hardness but it is determined by phenomena of material transfer vis-à-vis the mating material and the formation of protective oxide layers on the metallic-glass surface during sliding. This revised version was published online in August 2006 with corrections to the Cover Date.     

The Effect of Different Temperatures on Friction and Wear Properties of CFRPEEK against AISI 431 Steel under Water Lubrication

The tribological behavior of 30 vol% carbon fiber–reinforced polyetheretherketone (CFRPEEK) against AISI 431 steel under different temperatures of water lubrication was investigated. Friction and wear tests were carried out on a disc-on-disc contact test apparatus under different operating conditions. The results reveal that the lubricant temperature has a significant effect on the friction and wear properties of CFRPEEK sliding against AISI 431 steel. The average friction coefficient and wear rate of CFRPEEK increase with increasing lubricant temperature. However, the wear rate of AISI 431 steel did not have a positive correlation with the wear rate of CFRPEEK under different temperatures of water lubrication. Moreover, the original and worn surfaces of CFRPEEK and AISI 431 steel were imaged by environmental scanning electron microscopy and optical microscopy, respectively. The main tribological mechanisms of CFRPEEK sliding against AISI 431 steel were adhesive wear, and increasing the temperature of the lubricant could accelerate wear.     

The Performance of Heavily Loaded Oscillating Roller Bearings from 300 F to 600 F

Over 1000 roller bearings have been evaluated at elevated temperatures as oscillating bearings and load-life characteristics determined through statistical analysis of failure data. Operating temperatures of 300 F, 450 F, and 600 F were investigated. Bearing materials investigated included AISI 52100 steel, M-2 tool steel and 440-C stainless steel. Grease lubrication was used. The bearing load range included 250,000 psi to 500,000 psi maximum Hertz stress. AISI 52100 steel proved satisfactory for temperatures to 450 F. Tool steel (M-2) and 440 C stainless steel proved satisfactory for temperatures to 600 F. Although failure modes were predominantly by plastic deformation, wear and oxidation, failure distribution frequencies fit the Weibull distribution commonly used in bearing fatigue studies. Data scatter was less than that expected for continuously rotating ball bearings.     

Wear of steel in rolling contact with silicon nitride

Wear of steel (AISI M-50 and AISI 52100) bearing balls in lubricated rolling contact with ground and ground-and-lapped silicon nitride rods was studied using a ball-on-rod rolling-contact-fatigue (RCF) tester. The steel balls suffered significant wear in rolling contact with the as-ground (R_a = 0.18 μm) silicon nitride rods. The wear volume loss was approximately linear with the rolling distance. The wear rate increased linearly with the initial Hertzian contact stress in the range, 3–6.5 GPa. Examination of the wear tracks in a scanning electron microscope revealed surface features that suggested a wear mechanism that involved plastic deformation of the steel surface, squeezing of the metal symmetrically outward and rupture of the metal layers at the edges. The steel balls suffered negligible wear but failed by spalling in rolling contact with the ground-and-lapped silicon nitride rods (R_a = 0.08 μm) at an initial contact stress of 5.5 GPa. The as-ground silicon nitride rods exhibited neither wear nor spalling in the RCF tests, while the ground-and-lapped silicon nitride rods showed no wear but occasional spalling failure.     

Rolling Contact Fatigue and Sliding Wear Performance of Ferritic Nitrocarburized M-50 Steel

The rolling contact fatigue and sliding wear performance of two types of ferritic nitrocarburizing techniques (gaseous and fluidized bed) were evaluated on AISI M-50 steel. These processes produced a thin compound layer over a nitrogen-rich diffusion zone. It was observed that compound layer thicknesses less than 1 μm increased the rolling contact fatigue (RCF) L₁₀ life up to a factor of six over the untreated M-50 steel. Compound layers greater than 2 μm had a tendency to flake off the substrate near the spalled region, producing lower L₁₀ lives than the baseline M-50 steel. Sliding wear tests on ferritic nitrocarburized M-50 showed that the compound layer exhibited slightly larger friction coefficients than the nitrogen-rich diffusion zone, although this layer had slightly greater resistance to catastrophic wear at higher contact stresses.     

Sliding Friction and Wear Characteristics of Novel Graphitic Foam Materials

While the use of ORNL developed high-thermal-conductivity graphitic foam materials has been focused on thermal management applications, recent experiments have revealed their potential as bearing surfaces as well. The three primary tribological advantages are: (1) they can efficiently remove frictional heat, (2) their natural porosity can trap wear debris, and (3) their porosity can serve as a lubricant reservoir for the contact surface. A series of pin-on-disk experiments were conducted at both room temperature and 400 °C to compare the sliding friction and wear characteristics of the densified graphitic foam (mated against M-50 tool steel or against alumina) to those of conventional bearing materials like graphite, bearing bronze, poly- tetrafluoroethylene, bearing steel, and a Co-based superalloy. At room temperature and under low contact pressure, the tribological behavior of the densified graphitic foam material was comparable to that of graphite and better than that of other bearing materials. At 400 °C, traditional graphite exhibited a dusting wear regime accompanied by a high friction coefficient. In contrast, the graphitic foam demonstrated an ability to maintain low friction and wear at that temperature.     

Sliding wear of 100Cr6 in a diesel-lubricated flat–flat contact under realistic loads

The tribological limits of martensitic AISI 52100 steel were determined by the application of a wear-mapping technique based on the statistical design of experiments. Wear measurements were conducted on a pin-on-disc system lubricated with a low-lubricity diesel fuel, with both pin and disc constructed of the same AISI 52100 steel. The test bench was equipped with a displacement transducer and an accurate temperature control of the samples temperature, enabling low wear rates to be measured in situ by the displacement transducer without being perturbed by thermal dilatation. By this method it is possible to measure wear rates on the order of a few nm/h. Moreover, the wear of the disc was evaluated at the end of each test by profilometry. A statistical model was fitted to the obtained results. Combining the findings of several surface characterisation methods, we identified two active wear mechanisms: tribocorrosion at low contact pressures (15 N/mm²) and adhesive wear at higher loads. This conclusion was corroborated by examinations of wear particles carried out by scanning electron microscopy and transmission electron microscopy.     

GCr15及G20CrNi2Mo轴承钢高温润滑条件下摩擦磨损性能

为了探究轴承钢在高温润滑条件下的摩擦磨损性能,采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、洛氏硬度计等对GCr15高碳轴承钢和G20CrNi2Mo渗碳轴承钢组织、物相及硬度进行了表征,利用QG-700型气氛高温摩擦磨损试验机研究轴承钢材料不同条件下的高温润滑摩擦磨损性能,并分析其磨损机制.结果表明:2种轴承钢...     

玻璃陶瓷材料与轴承钢表面摩擦磨损的试验研究

在盘销式摩擦磨损试验机上考察了氟金云母玻璃陶瓷与轴承钢的摩擦磨损性能,在不同载荷条件下,测试了摩擦因数和玻璃陶瓷的磨损率,用金相显微镜观察和分析磨损表面形貌,并探讨了玻璃陶瓷材料的磨损机制。结果表明：在低载荷条件下,摩擦因数较低;随着载荷的增加,摩擦副的摩擦因数比较稳定,氟金云母玻璃陶瓷与轴承钢的平均摩擦因数为0.095。玻璃陶瓷和轴承钢的磨损率存在波动,其对磨过程以磨料磨损为主。     

Wear Mechanism of Cemented Carbide Tool in High Speed Milling of Stainless Steel

Adhesion of cutting tool and chip often occurs when machining stainless steels with cemented carbide tools. Wear mechanism of cemented carbide tool in high speed milling of stainless steel 0Cr13Ni4 Mo was studied in this work. Machining tests on high speed milling of 0Cr13Ni4 Mo with a cemented carbide tool are conducted. The cutting force and cutting temperature are measured. The wear pattern is recorded and analyzed by high?speed camera, scanning electron microscope(SEM) and energy dispersive X?ray spectroscopy(EDS). It is found that adhesive wear was the dominant wear pattern causing tool failure. The process and microcosmic mechanism of the tool's adhesive wear are analyzed and discussed based on the experimental results. It is shown that adhesive wear of the tool occurs due to the wear of coating, the a nity of elements Fe and Co, and the grinding of workpiece materials to the tool material. The process of adhesive wear includes both microcosmic elements di usion and macroscopic cyclic process of adhe?sion, tearing and fracture.     

国产牙钻混合陶瓷球轴承性能评估分析

应用自建的牙钻轴承试验机对某国产牙钻混合陶瓷球轴承的使用寿命进行了试验评估,并与全钢轴承进行了对比试验,对轴承失效原因进行了分析.试验结果表明,在相同试验工况下,混合陶瓷球轴承的使用寿命低于全钢轴承,但是其沟道表面的磨损情况优于全钢轴承.经分析,导致国产混合陶瓷球轴承使用寿命下降的主要原因是保持架的提前失效.     

The tribological behavior of Ni–Cu–Ag-based PVD coatings for hybrid bearings under different lubrication conditions

In a cryogenic environment, components like bearings with interacting surfaces in relative motion (tribosystems) often generate undesired heat and experience high wear. Because the properties of conventional bearing materials like stainless steel cannot be applied to this temperature range, the PVD coating based on metal–metal pairs with better frictional properties must be employed. To test the suitability of the Ni–Cu–Ag-based PVD coatings of hybrid bearings for liquid rocket engine turbopumps and to obtain reliable coating material data in the extreme environment, the tribological behaviors of coatings under the cryogenic fluid (liquid oxygen and liquid nitrogen) and water lubricated conditions are studied, respectively. In the paper, the specimens are in a vibrocryotribometer with the ball-on-plane contact type, and various running conditions in terms of lubricants, contacting loading, and contacting velocity are examined. The simulated experiment for testing the actual tribological performance of Ni–Cu–Ag-based PVD coatings for hybrid bearings is tested. The results of the tests indicate that the coatings can be suitable for cryogenic tribosystems of turbopumps. In the cryogenic environment, the volume wear rate of coatings increases rapidly with the contacting loading, but 15 min later, the volume wear volume of coatings turns into 2.5–15×10⁻⁴ mm³. Besides, under the liquid oxygen condition in simulating the liquid rocket engine turbopumps environment, the friction coefficients are 0.03–0.1.     

Improvement of the seizure resistance of orifice-type aerostatic bearings (case study)

In this case study, professional equipment installed at several different sites was suffering from recurring seizure of the aerostatic thrust bearings of a linear motor, causing unacceptable downtime and production losses. It was necessary to find a rapid and cost-effective solution that could be applied to equipment already installed in the field, as well as an optimum design solution for new equipment. Analysis of the field failures indicated that failure was due to either the magnetic attraction and trapping of contaminant particles between the thrust pads and bearing track surfaces, initiating adhesive wear and material transfer, or to (temporary) air supply failures or overloading, resulting in contact between the bearing surfaces. The pre-selection of potential solutions to the problem was aimed at reducing both the particle contamination and the tendency for adhesive wear behaviour. Pin-on-disk tests were carried out in order to rapidly identify potential solutions. These tests were followed by actual-scale system tests simulating the crashing of air bearings and the influence of contaminant particles introduced into the bearing gap.The most favourable results in terms of performance and costs were achieved by applying a thermo-chemical carbon diffusion surface treatment (Kolsterising^®) to thrust bearings made of austenitic stainless steel, and applying a pulse plasma nitriding treatment to the bearing track material. This was chosen as the preferred solution for new equipment design. For equipment already installed in the field, a satisfactory solution was provided by replacing the existing thrust pads with pads equipped with partially stabilised zirconia (PSZ) plates on the bearing surfaces.     

The microstructure and wear behaviour of friction stir processed AISI 430 ferritic stainless steel

ABSTRACT

The microstructure and wear behavior of Friction Stir Processed (FSPed) AISI 430 ferritic stainless steel were analyzed in the present study. FSP was performed with a tool rotation and advancing speeds of 1400?rpm 16?mm/min respectively by employing a tungsten carbide tool. The FSPed microstructure consisted of a mixture of ferrite and martensite. After FSP, microhardness increased with respect to that of the as-received material. The wear resistance of the FS processed material was significantly enhanced if compared to that of the as-received substrate. According to the SEM analyses of the worn surfaces and wear debris, a combination of adhesive wear and delamination was observed in the case of the base metal. The wear mechanism shifted to mild adhesive wear after FSP. The superior wear resistance of the FS processed AISI 430 steel was attributed to the pronounced grain refinement and to martensite formation in the stir zone.     

Investigation of friction units of nuclear plants operating in heavy high-temperature liquid-metal heat carriers. Part 2. Experimental results

The tribological problems posed by heavy liquid-metal heat carriers used in the circuits of nuclear power plants are discussed. The results of experimental study of the vibrational wear of heat-exchanging tubes in the interfaces with the spacing grates are presented. These results are applicable for testing the vibrational strength of the steam generator of a fast neutron reactor with lead heat carrier. Experimental investigation and service-life tests of involute-profile cylindrical tooth gears and sliding bearings working in fast neutron reactors containing the lead heat carrier are conducted. Experimental and theoretical study is performed on the wear of steel and cast-iron sliding bearings in the recycling pumps of reactors operating in lead, eutectic lead-bismuth and lead-lithium alloys. It is shown experimentally that the tooth gears from 40X13 steel and SCh20 grey iron are capable of operating in the lead heat carrier for 500 and 400 hours, respectively, at the temperature 450°C when the concentration of thermodynamically active oxygen in the lead is close to saturation, the contact stress in the gearing is 758 MPa, the gear rotational frequency is 500 min⁻¹ or less, and the gear ratio is 1.5 (the peripheral velocity of the gear and the wheel over the pitchline is 2.1 m/s). The likely causes of destruction of the gear teeth are adhesive wear and insufficient heat resistance (refractorability) of the tooth material at 450–500°C.     

The effects of plasma nitriding process parameters on the wear characteristics of AISI M2 tool steel

The main aim of this work is to evaluate the effects of the plasma nitriding process on AISI M2 tool steel. In previous work, treatment time and temperature were varied to identify the treatment conditions for good wear behaviour. In the present work, the treatment time was fixed while temperature and gas pressure were varied. Samples were characterised by glow discharge optical spectroscopy, scanning electron microscopy, X‐ray diffraction, surface microhardness and wear test. The specimens nitrided at 400 and 900 Pa showed the best wear performance, which is possibly due to reduction of the friction coefficient and the low adhesive wear observed. Samples processed at 200 Pa showed spalling during the wear test, indicating a brittle surface. This revised version was published online in July 2006 with corrections to the Cover Date.     

Microstructural aspects determining the adhesive wear of tool steels

In many machining applications, adhesion of the workpiece to the tool is a major problem. Adhesion may be reduced by changing the microstructure of the tool steel, e.g. by increasing the carbide content. The present work deals with the influence of some microstructural parameters in the adhesive wear of tool steels. The investigations were conducted using six model alloys based on the powder metallurgy high speed steel AISI M4, all of which had the same martensitic matrix composition after heat treatment. The alloys had MC carbide contents which varied between 0 and 25 mol% in 5 mol% increments. Ball-on-disc experiments were carried out in ambient air at room temperature using austenitic stainless steel and aluminum balls as counterfaces. Wear tracks on the disks were characterized using both a scanning electron microscope and an optical profiler. The results show that two main parameters determine the adhesive wear behavior: the carbide content and the distance between carbides.     

The effect of hard coated metals on the thermo‐oxidative stability of a branched perfluoropolyalkylether lubricant

M‐50 and carburized Pyrowear 675® (Carpenter Technology, Reading PA, USA) steel coupons deposited with commercially available physical vapour deposited TiN, TiCN, TiAlCN, TiCrCN/TiB₄C multilayer, electroless Ni (E‐Ni) TiN and E‐Ni TiCN coatings were immersed in a branched perfluoropolyalkylether (PFPAE), Krytox AC® (E.I. du pont de Nemours and Company, Wilmington DE, USA), in an oxidative environment at temperatures ranging from 315 to 360 °C for a duration of 24 hours and compared with uncoated coupons. Coated and uncoated Pyrowear 675® coupons demonstrated superior corrosion resistance compared with coated and uncoated M‐50 respectively. The coatings most resistant to chemical attack in the PFPAE fluid were TiCN, E‐Ni TiN and E‐Ni TiCN. Copyright © 2006 John Wiley & Sons, Ltd.