Development, characterization and testing of tungsten doped DLC coatings for dry rotary swaging

Hasselbruch, Henning; Herrmann, Marius; Mehner, A.; Zoch, H.‐W.; Kuhfuß, Bernd

doi:10.1051/matecconf/20152108012

Cited by 11 publications

(5 citation statements)

References 11 publications

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“…The material in its initial state was exposed to residual stress relaxation heat treatment, thus it can be assumed that the observed residual stress fluctuations result from the rotary swaging process as postulated in the previous section. Furthermore, additional experiments were performed using dies with a diamond-like carbon (DLC) coating [25] and without the rough tungsten carbide coating. The DLC coating had a thickness of 2.2 μm and an indentation hardness H IT of 18 GPa.…”

Section: Resultsmentioning

confidence: 99%

Influence of Process Fluctuations on Residual Stress Evolution in Rotary Swaging of Steel Tubes

et al. 2019

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Infeed rotary swaging is a cold forming production technique to reduce the diameter of axisymmetric components. The forming is achieved discontinuously by a series of radial strokes that are spread over the shell of the part. Due to tolerances within the rotary swaging machine, these strokes perform individually and the resulting stroke pattern is not homogeneous with regards to circumferential and longitudinal distribution. Nevertheless, in combination with the high number of performed strokes and the large contact area between the dies and the part, the external part properties, such as diameter, roundness and surface roughness, show even values along the finished part. In contrast, strength-defining internal part properties, like microstructure and residual stress components, are more sensitive to the actual pattern and temporal sequence of the individual strokes, which is investigated in this study. The impact of process fluctuations during the conventional process, which are induced by the tolerances of machine tool components, was verified by numerical simulations, physical tests and measurements of residual stress distributions at the surface and at depth. Furthermore, a method is introduced to maintain the stroke following angle ∆φ at zero by flat dies, and thus the actual pattern and temporal sequence of the strokes was homogenized. The results show that the residual stress fluctuations at the surface could be controlled and reduced. Furthermore, it is demonstrated that the depth profile of the residual stresses at a distance of 300 µm from the surface developed independently from the process fluctuations.

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Section: Resultsmentioning

confidence: 99%

Influence of Process Fluctuations on Residual Stress Evolution in Rotary Swaging of Steel Tubes

et al. 2019

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“…This objective is designed to increase the fracture toughness of the whole coating system and to increase the hardness stepwise [15]. Finally, a hard functional a-C:H layer of about 22 GPa HIT0.01 is applied for ensuring low dry coefficients of friction of µ < 0.2 and wear against steel and aluminum counter bodies of k < 3•10 -7 mm³/Nm [16]. In general, a-C:H coatings have a low tendency to adhesion due to the saturation of carbon bonds by hydrogen of the OH groups on the surface [17,18].…”

Section: A-c:h:w/a-c:h Pvd Coatingmentioning

confidence: 99%

“…The precursor gas acetylene (C2H2) is used for deposition of the a-C:H:W and a-C:H layers. Further details of the deposition process are published in previous publications [16,19]. In figure 9 a) the used target configuration is shown in order to apply the mentioned a-C:H:W/a-C:H coating system on a substrate material.…”

Section: Reactive Magnetron Sputtering Device For A-c:h:w/a-c:h Coatingmentioning

confidence: 99%

A new approach for dry metal forming: CO2 as volatile lubrication in combination with hard and low friction coatings

et al. 2018

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Nowadays, it is more important than ever to meet the increasing technical and statutory requirements and to develop new process strategies. In sheet metal forming the low consumption of oil lubrication gets an increasingly important role. The aim in sheet metal forming is to reduce the amounts of lubricants. In the long term, the future sheet metal processing should be able to completely dispense without mineral oil-containing lubricants. Two promising approaches for a dry process design are combined in this paper for the first time and the fundamental feasibility of this new hybrid technology is shown. On the one hand, a novel approach for temporary lubrication of deep-drawing processes with CO2 as a volatile medium is used. On the other hand, it is supported by the application of an additional hard coating system such as a silicon nitride (Si3N4) or tungsten doped a-C:H multilayered (Cr/CrNx/a-C:H:W/a-C:H) coating system to further reduce tool wear and wear debris of the formed sheets made of DC04 (mat. no.: 1.0338). The results show a low coefficient of friction and reduced wear. Especially for the carbon coating system, there is minor tool wear at a higher surface pressure. By means of the graphite constituent, even a smoothening of the roughness peaks can be recorded. The next step would be the implementation of this hybrid technology on a tool for deep drawing a rectangular cup.

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“…Functionalized rotary swaging dies were introduced, exhibiting both hard coated and structured surfaces to encounter complex and opposing tribological requirements [2]. Tungsten doped amorphous diamond like carbon coatings (a-C:H:W) with additional a-C:H top layer characterized by excellent hardness and fracture toughness were applied to forming dies for friction reduction and wear protection [3,4]. Furthermore, macro structured reduction zones of forming dies were used to control the axial reaction force that counteracts the feed force.…”

Section: Introductionmentioning

confidence: 99%

Reducing Abrasive Particle Generation in Dry Rotary Swaging by Utilizing DLC Hard Coated Dies

et al. 2018

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The emphasis of this paper is the investigation of the impact of the diamond like carbon (DLC) hard coating system on the amount of abrasive particles being generated during dry rotary swaging. Rotary swaging experiments applying coated and uncoated macro structured forming dies were carried out against aluminum and steel work pieces varying the process parameter feed velocity. It was found that DLC coatings effectively reduce the generation of abrasive particles from the work piece. For dry machining of aluminum the amount was reduced to a tenth of the original quantity achieved with uncoated dies. The results are discussed with regard to the mechanics of interfacing surfaces. Additionally, forming dies exhibiting macro structures surfaces of improved design were introduced and applied in dry rotary swaging experiments, which allowed minimizing the abrasive particle generation.

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Development, characterization and testing of tungsten doped DLC coatings for dry rotary swaging

Cited by 11 publications

References 11 publications

Influence of Process Fluctuations on Residual Stress Evolution in Rotary Swaging of Steel Tubes

Influence of Process Fluctuations on Residual Stress Evolution in Rotary Swaging of Steel Tubes

A new approach for dry metal forming: CO2 as volatile lubrication in combination with hard and low friction coatings

Reducing Abrasive Particle Generation in Dry Rotary Swaging by Utilizing DLC Hard Coated Dies

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