A compression-torsion-wear-test achieving contact pressures of up to eight times the initial flow stress of soft aluminium

Teller, Marco; Bambach�, Markus

doi:10.1016/j.cirp.2015.04.086

Cited by 14 publications

(10 citation statements)

References 10 publications

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“…The sliding wear behavior against aluminum was investigated using a ball-on-disk test (CSM Instruments SA, Peuseux, Switzerland, Figure 1a) [16,41,42], where aluminum balls (Al 99.5) of 6 mm in diameter loaded with 0.242 N normal force were rubbed over the functionalized Cu-O coated steel disks with a sliding speed of 1 mm/s for 5 m on a 14 mm wide circular track ( Figure 1b) to resemble the contact pressure in Al cold forging [22,43,44]. As great challenges in liquid lubricant-free Al-forming processes are Al-sticking and adhesion [15,19,21], ball-on-disk tests were carried out for 5 m of sliding distances to appraise the influence of molecular coverage on the tribological behavior.…”

Section: Tribology Testingmentioning

confidence: 99%

Molecular Coverage Determines Sliding Wear Behavior of n-Octadecylphosphonic Acid Functionalized Cu–O Coated Steel Disks against Aluminum

et al. 2020

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The sliding wear behavior of Cu–O coated steel disks functionalized with n-octadecyl-phosphonic acids was evaluated against aluminum in ball-on-disk tribometer experiments. After 5 m of sliding the friction coefficient of the functionalized sample with maximum molecular coverage is ≤0.3 ± 0.1. Surfaces with lower coverage mitigate friction and wear as well exhibiting initially similar low friction coefficients but reveal the breakdown of lubrication for sliding distances <5 m. The length of the low friction sliding distance before breakdown scales with the coverage of n-octadecylphosphonic acids on the Cu–O surface. Coverage hence determines the tribological behavior of the functionalized surface against sliding aluminum. As the coverage is increased, detrimental asperity contacts between the rubbing surfaces are reduced.

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Section: Tribology Testingmentioning

confidence: 99%

Molecular Coverage Determines Sliding Wear Behavior of n-Octadecylphosphonic Acid Functionalized Cu–O Coated Steel Disks against Aluminum

et al. 2020

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“…The workpiece specimen enables a surface expansion and as a result the break-up of the oxide layer. The work presented in [12] depicts further details regarding the compression-torsion-wear tribometer.…”

Section: Specimen Preparation 21 Tribometer Specimensmentioning

confidence: 99%

“…The surfaces of the tribometer specimens are measured with a Zygo NewView 7300 white light interferometer. Due to the known boundary effects at the specimens' outer radius [12], only the surface within an inner radius of 5 mm is evaluated. Figure 7 shows the resulting contact surfaces of the different surfaces with and without SAM coating after the test.…”

Section: Wli Surfacesmentioning

confidence: 99%

Probing the potential of structured and surface functionalized tools for dry cold forging of aluminium

et al. 2018

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In order to reduce friction and wear in cold forging of aluminium and its alloys a tremendous amount of lubricants is used. The main task of the liquid lubricants is the separation of tool and workpiece surfaces to avoid adhesion and abrasion. From an ecological and economical point of view, a reduction of the consumption of lubricants is meaningful. Novel surface modification techniques have been investigated to enable dry cold forming. In previous work, a reduced wear by adhesion of aluminium to an AISI H11 ESR tool steel surface was detected for a combination of laser polishing and a subsequent surface functionalization. Here, structured surfaces combined with surface functionalization are investigated regarding their wear behaviour. Therefore, different structures are realized on AISI H11 ESR tool steel surfaces by laser structuring. These structures are aligned parallel and perpendicular to the material flow direction. Furthermore, different structure depths are generated. It is evident that the laser induced surface melting causes both, a reduced micro roughness as well as a homogenized elementary distribution. Moreover, the surfaces are functionalized with an octadecylphosphonic acid selfassembled monolayer (C18PA-SAM). The SAM’s distal alkyl termini functionalize the tool steel surface und thus only weak van-der-Waals interactions are present in the aluminium-tool steel interface rendering an interaction, which is expected to be similar to the interaction in conventionally lubricated aluminium forming. Finally, the surfaces are appraised regarding their wear behaviour in a compression-torsion-wear tribometer. The different experimental results document the potential of the here investigated combined tool surface modification. Although, the performance of a lubricated process is not completely reached a reduction in friction and wear can be achieved compared to unmodified tools.

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“…The surface enlargement supports a higher lubricant capacity and at the same time provides a lubricant film throughout the forming process by means of lubricant pockets [4]. In order to raise the process productivity of cold forming even further and at the same time reduce ecological problems of lubricants, cold forging without lubricants is investigated [5]. Cold forging without lubricants would reduce process steps as applying and removing of lubricants as well as recycling steps [5].…”

Section: Introductionmentioning

confidence: 99%

“…In order to raise the process productivity of cold forming even further and at the same time reduce ecological problems of lubricants, cold forging without lubricants is investigated [5]. Cold forging without lubricants would reduce process steps as applying and removing of lubricants as well as recycling steps [5]. Due to the absence of lubricants the process loads may increase substantially and could cause damage to the tools or deteriorate the process [6].…”

Section: Introductionmentioning

confidence: 99%

Influence of surface integrity on the plastic flow in analogous testing of 42CrMo4

et al. 2018

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Surface modification of workpieces for cold forming processes is common in industrial practice. Specific surface topographies manufactured by means of shot peening form lubricant pockets, which provide a continuous lubricating film throughout the process. Furthermore, hydrostatic as well as hydrodynamic lubrication effects emerge, which further reduce the friction during the process and protect the tool from wear effects. These effects are well researched and applied in order to enable cold forming processes. In dry forming processes, no lubricants are used, and the positive lubrication effects do not appear. Surface modifications by shot peening or knurling change surface integrity in terms of hardness, residual stresses and geometry. The effects of the changed surface integrity on the forming process are not researched. In tribometer tests, a hard and rough surface texture lead to a lower frictional shear stress, whereas a rather smooth and hard surface texture leads to a lower punch force in an extrusion process. The mechanisms between surface textures and the smoothing and forming process are unknown. Furthermore, findings of the tribometer tests cannot be fully transferred to the extrusion process. As in tribometer tests a pin is used as tool and in extrusion a whole die, a discrepancy between the most suitable surface texture for a friction reduction results out of different flow conditions. Still, the tribometer tests give a first reference on a surface pretreament. The paper deals with an investigation of surface textures in order to distinguish characteristics of surface textures respectively a friction reduction. By means of indentation tests of the quenched and tempered steel 42CrMo4 the plastic flow in dependency of different surface integrities are researched. The results show which characteristics help to lower the punch force the most, so for further investigations an optimized surface modification is set up in order to enable a dry metal forming process.

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A compression-torsion-wear-test achieving contact pressures of up to eight times the initial flow stress of soft aluminium

Cited by 14 publications

References 10 publications

Molecular Coverage Determines Sliding Wear Behavior of n-Octadecylphosphonic Acid Functionalized Cu–O Coated Steel Disks against Aluminum

Molecular Coverage Determines Sliding Wear Behavior of n-Octadecylphosphonic Acid Functionalized Cu–O Coated Steel Disks against Aluminum

Probing the potential of structured and surface functionalized tools for dry cold forging of aluminium

Influence of surface integrity on the plastic flow in analogous testing of 42CrMo4

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