Ytterbium impulse laser for surface modification of tool steel with B4C-Al powders

Abstract The paper deals with a new application solution of Ytterbium Picosecond Pulsed Fiber Laser for surface modification of 3Kh2V8F hot-work tool steel (the analog of AISI H21 steel). Surface modification was conducted by B4C-Al powders from preplaced pastes followed by laser heating. The ratio of B4C-Al powders was taken as 5/1 by weight and the paste thickness was approximately 1 mm. Laser treatment was conducted according to the following parameters: 1070 nm of wavelength, 100 W of power, 1 mJ of pulse energy, 100 ns pulse duration, pulse frequency range from 50 kHz to 90 kHz. Several tracks with different widths were obtained as a result of treatment depending on velocity of the laser move. EDS analysis showed that B4C particles were not completely dissolved in the weld beads. However, an enhanced concentration of boron (8-12 wt.%) was revealed in the vicinity of B4C particles. The aluminum concentration was low (up to 0.79 wt.%) on the surface of the weld beads.

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

MATEC Web of Conferences ◽

10.1051/matecconf/201819014010 ◽

2018 ◽

Vol 190 ◽

pp. 14010

Author(s):

Marco Teller ◽

Ingo Ross ◽

Stephan Prünte ◽

André Temmler ◽

Moritz Küpper ◽

...

Keyword(s):

Surface Modification ◽

Tool Steel ◽

Surface Functionalization ◽

Friction And Wear ◽

Steel Surface ◽

Cold Forging ◽

Wear Behaviour ◽

Main Task ◽

Cold Forming ◽

Structured Surfaces

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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