Porosity Effect of Sintered Steel on the Frictional Performance of Conformal and Nonconformal Lubricated Contacts

Boidi, G.; Tertuliano, I.S.; Lima, Leandro Gregorut; Profito, Francisco J.; Machado, Izabel Fernanda

doi:10.1080/10402004.2019.1640917

Cited by 10 publications

(37 citation statements)

References 38 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: 59%

“…(a) (b) Figure 5.9 -Wear track geometrical dimensions (depth and width) of the sintered and NP disks after roller-on-disk tests, adapted from [21].…”

Section: Roller-on-diskmentioning

confidence: 99%

“…10 -SEM surface images of D8 sintered disk (a) before roller-on-disk tests and wear tracks after testing using (b) SRR 89% and (c) 131%, adapted from[21]. 67.…”

mentioning

confidence: 99%

“…(a) Schematic of Bruker tribometer for lubricated tests in the roller-on-disk configuration. Details of (b) SRR device and (c) test set up configuration, adapted from[21].…”

mentioning

confidence: 99%

“…11 -E/H ratio for NP and sintered disks, adapted from[21].•Ball-on-diskFriction map surface (COF x x SRR) could be obtained similarly to those studied for textured material (see Section 4.5.2), however main results are depicted here as "Stribeck like" curve (COF x with fixed values of SRR) to better visualize and quantify difference between sample frictional behaviour. Friction trends did not change with varying SRR conditions, therefore results of both sintered disks and balls were presented for "boundary" test condition (SRR 5% and SRR 120%).…”

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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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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: 59%

“…(a) (b) Figure 5.9 -Wear track geometrical dimensions (depth and width) of the sintered and NP disks after roller-on-disk tests, adapted from [21].…”

Section: Roller-on-diskmentioning

confidence: 99%

“…10 -SEM surface images of D8 sintered disk (a) before roller-on-disk tests and wear tracks after testing using (b) SRR 89% and (c) 131%, adapted from[21]. 67.…”

mentioning

confidence: 99%

“…(a) Schematic of Bruker tribometer for lubricated tests in the roller-on-disk configuration. Details of (b) SRR device and (c) test set up configuration, adapted from[21].…”

mentioning

confidence: 99%

mentioning

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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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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The use of Powder Metallurgy for promoting friction reduction under sliding-rolling lubricated conditions

Boidi

Profito

Kadiric

et al. 2021

Tribology International

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Porosity Effect of Sintered Steel on the Frictional Performance of Conformal and Nonconformal Lubricated Contacts

Cited by 10 publications

References 38 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

The use of Powder Metallurgy for promoting friction reduction under sliding-rolling lubricated conditions

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