Tribological Evaluation of Sintered and Conventional Gear Materials

Boidi, G.; Tertuliano, I.S.; Cano, Michell F.; Machado, G.A.A.; Souza, R.M.; Machado, Izabel Fernanda

doi:10.4271/2017-36-0153

Cited by 10 publications

(19 citation statements)

References 29 publications

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“…3 The essential information for understanding the research was reported here, and complementarily the main results obtained has been already published elsewhere [18][19][20][21][22][23].…”

Section: Research Questionsmentioning

confidence: 66%

“…Besides total (volume) porosity, also pore distribution and main geometrical characteristics should be considered [15,22,23].…”

Section: Porosity and Pore Morphology Measurementsmentioning

confidence: 99%

“…Surface pores similarly to textured features could promote lubrication in severe conditions (lubricant reservoirs), reduce wear (debris trapping) and potentially increase lubricant local viscosity and hydrodynamic pressure (micro hydrodynamic bearing effect). Surface pores are randomly distributed and generally assumed an irregular shape (see Figure 5.1), therefore the micro bearing effect is plausible just for pores of reduced dimensions with regular rounded shape [23]. Furthermore, large porosity networks with connected porosity and irregular shape of surface pores could promote crack propagation for high contact pressure tests (HEHL).…”

Section: Tribological Effect Of Surface Porosity In Pm Materialsmentioning

confidence: 99%

“…These factors could avoid micro bearings effects and even disturb hydrodynamic pressure distribution, causing worse results compared to untextured surfaces. Furthermore, more porous samples (IP and LP) also had rougher surfaces that negatively affected tribological performances[23].…”

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An experimental assessment of surface micro irregularities (porosity and texture) effects on tribological behaviour under lubricated conditions.

Boidi¹

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recent years, although this procedure usually implies extra manufacturing operations and costs. On the other hand, sintered materials contain themselves surface cavities that could potentially act as surface texture and, consequently, lead to friction reduction. This research aims to extend the current knowledge on the tribological influence of micro surface irregularities (pores and laser texture) under lubricated experimental tests and explore the use of these features for tribological applications. Samples were manufactured using both sintering and texturing processes to obtain different surface characteristics. Three different porosity conditions were produced for sintered steels, whereas grooves and dimples configurations were designed for textured steel samples. After that, experimental tests were performed under varying sliding-rolling conditions (from prevalent rolling to prevalent sliding) especially using non-conformal contact. Speed was also varied during frictional tests to cover a wide range of operational conditions and verify the effects of surface features under different lubrication regimes. Friction tests were carried out with two tribometers using configurations of pin-on-disk, roller-on-disk and ball-on-disk. Film thickness was measured by an ultra-thin optical interferometry rig using a methodology properly designed for rough samples. Samples with smooth surfaces were utilized as a reference bench to be compared to material with surface modification (texture or porosity). Main results showed that the decrease of porosity led to friction reduction in the sintered steel. Material with reduced porosity performed even better than reference smooth samples. In addition, the dimple configuration promoted friction reduction, whereas grooves generally performed similarly or worse than reference material. Even if textured dimples and small porosity on sintered material were produced by different techniques, they presented similar geometrical characteristics and consequently they both reduced friction compared to reference samples. As part of the outcome, main results were mapped to better understand the effect of each surface feature on tribological performance. Furthermore, a preliminary phenomenological model was proposed to predict frictional response of surface with micro cavities (pores or texture) from reference steel results. Main findings suggest that the effect of tailored surface cavities could be somehow compared to randomly distributed ones, even if produced by very different manufacturing techniques.

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“…3 The essential information for understanding the research was reported here, and complementarily the main results obtained has been already published elsewhere [18][19][20][21][22][23].…”

Section: Research Questionsmentioning

confidence: 66%

“…Besides total (volume) porosity, also pore distribution and main geometrical characteristics should be considered [15,22,23].…”

Section: Porosity and Pore Morphology Measurementsmentioning

confidence: 99%

Section: Tribological Effect Of Surface Porosity In Pm Materialsmentioning

confidence: 99%

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An experimental assessment of surface micro irregularities (porosity and texture) effects on tribological behaviour under lubricated conditions.

Boidi¹

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“…The tribological response of porous materials not only depends on the total porosity, but also on pore characteristics such as average pore dimensions, distribution, connectivity, and shape [20][21][22]. For this work, the pore area fraction (fraction of area occupied by the pores expressed as a percentage) as a function of pore size was evaluated by optical analysis.…”

Section: Bearing Materials and Lubricantsmentioning

confidence: 99%

Identification of a Material–Lubricant Pairing and Operating Conditions That Lead to the Failure of Porous Journal Bearing Systems

2020

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In this study, we perform accelerated wear tests with porous journal bearings (PJBs) on a lab test rig, providing statistically reliable results under realistic operational conditions. To this end, a custom-made tribometer consisting of 5 mechanically independent but centrally controlled units was used to test five identical bearings in parallel. The test parameters were tuned to promote enough wear under mixed lubrication by increasing the clearance gap and the radial load, while minimizing the bidirectional rotational speed. A wide range of lubricant and material combinations were evaluated, the vast majority of which performed excellently (i.e., negligible wear and low friction). Only one notable combination of a low-density iron bearing paired with a standard PAO-based lubricant failed when operating at low rotational speeds, exhibiting highly unstable frictional behavior and 10–20 times the typical wear in practical applications. An analysis of Stribeck curves, recorded periodically during the wear tests as a diagnostic tool, proved that this particular combination of materials and parameters failed to run in properly, with deteriorating tribological behavior over time. A direct relation between the total wear and the maximum temperature in the tribocontact during testing helped identify this pairing as the only one operating solely under mixed lubrication (high asperity contact), explaining the excessive wear. Graphical Abstract

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Electrochemical machining process for micropit arrays using a rolling device with a linear cathode and a soft mask

Meng

Liu

et al. 2023

Int J Adv Manuf Technol

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This paper presents a novel electrochemical machining process for machining microstructure arrays on curved surfaces of parts. A set of electrolytic systems with the rolling device was constructed to machine micro-pit arrays on various metal part surfaces. Numerical simulations were conducted to investigate the electric field distribution characteristics and their spatial evolution over time, as well as the geometric profile evolution of the forming microstructures. Experimental tests were carried out on the surface of a 304 stainless steel workpiece using a 10% NaNO3 electrolyte and a 0.1 mm electrode gap. The effects of voltage, the rotating speed of the roller and the linear cathode size on the morphology of micro-pit arrays were explored. The results showed that micro-pit arrays could be successfully machined on the plane, outside and inside surface of the workpiece. Under the 10.5 V applied voltage and 0.2 r/min rotating speed of the workpiece, the diameter of the micro-pit was 421.55±18.75 μm, the depth was 70.2±4 μm, the average etch factor(EF) was 1.16, and the roughness of the micro-pit was 0.625±0.205 μm. This work provides a promising strategy for high-precision batch machining micro-pit arrays on the plane and curved surfaces of the workpiece.

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Tribological Evaluation of Sintered and Conventional Gear Materials

Cited by 10 publications

References 29 publications

An experimental assessment of surface micro irregularities (porosity and texture) effects on tribological behaviour under lubricated conditions.

An experimental assessment of surface micro irregularities (porosity and texture) effects on tribological behaviour under lubricated conditions.

Identification of a Material–Lubricant Pairing and Operating Conditions That Lead to the Failure of Porous Journal Bearing Systems

Electrochemical machining process for micropit arrays using a rolling device with a linear cathode and a soft mask

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