The use of holographic optical elements (HOE's) to investigate the use of a flat irradiance profile in the control of heat absorption in wire-fed laser cladding

Goffin, Nicholas J.; Higginson, R.L.; Tyrer, John R.

doi:10.1016/j.jmatprotec.2015.01.023

Cited by 20 publications

(25 citation statements)

References 18 publications

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“…This was considered to be a suitable substitute for a pedestal beam, in line with results for expanded beams found by Goffin et al. [16]. The Nd:YAG laser, with wire feeder attached is shown in figure 5.…”

Section: Methodsmentioning

confidence: 99%

“…Experimentation is presented in two phases:

— The first phase picks up where Goffin et al. [16] left off, using pre-placed wire for the purposes of directly comparing heat flow between the two wire shapes in order to study the heat flow and track formation on their own, in isolation from realistic processing conditions.

— The second phase incorporates a wire feeder into the process and compares the two wire shapes under realistic processing conditions without using HOEs. These results are then developed with the demonstration and characterization of multilayer stacking using shaped wire.…”

Section: Introductionmentioning

confidence: 99%

“…[16] left off, using pre-placed wire for the purposes of directly comparing heat flow between the two wire shapes in order to study the heat flow and track formation on their own, in isolation from realistic processing conditions.…”

Section: Introductionmentioning

confidence: 99%

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Using wire shaping techniques and holographic optics to optimize deposition characteristics in wire-based laser cladding

2016

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In laser cladding, the potential benefits of wire feeding are considerable. Typical problems with the use of powder, such as gas entrapment, sub-100% material density and low deposition rate are all avoided with the use of wire. However, the use of a powder-based source material is the industry standard, with wire-based deposition generally regarded as an academic curiosity. This is because, although wire-based methods have been shown to be capable of superior quality results, the wire-based process is more difficult to control. In this work, the potential for wire shaping techniques, combined with existing holographic optical element knowledge, is investigated in order to further improve the processing characteristics. Experiments with pre-placed wire showed the ability of shaped wire to provide uniformity of wire melting compared with standard round wire, giving reduced power density requirements and superior control of clad track dilution. When feeding with flat wire, the resulting clad tracks showed a greater level of quality consistency and became less sensitive to alterations in processing conditions. In addition, a 22% increase in deposition rate was achieved. Stacking of multiple layers demonstrated the ability to create fully dense, three-dimensional structures, with directional metallurgical grain growth and uniform chemical structure.

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Section: Methodsmentioning

confidence: 99%

“…Experimentation is presented in two phases:

Section: Introductionmentioning

confidence: 99%

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Using wire shaping techniques and holographic optics to optimize deposition characteristics in wire-based laser cladding

2016

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“…where K is the thermal conductivity of single-pass, T is the liquid temperature of the alloy, T0 is the According to the rapid solidification theory, the change of the microstructure is mainly influenced by the constitutional undercooling, which has a negative relationship with the ratio of temperature Coatings 2020, 10, 76 8 of 20 gradient G and solidification velocity R, and the grain refines as the cooling rate G × R increases [23,24]. The relationship can be expressed as Equations (5) and (6) [25,26].…”

Section: Phase Constitution and Microstructure Characteristicsmentioning

confidence: 99%

Effects of Process Parameters on Geometrical Characteristics, Microstructure and Tribological Properties of TiB2 Reinforced Inconel 718 Alloy Composite Coatings by Laser Cladding

et al. 2020

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The TiB2 reinforced Inconel 718 alloy composite coatings were prepared on carbon steel by laser cladding. The energy input (the ratio of laser power and scanning speed, E) was introduced to investigate the effects of process parameters on geometrical characteristics, microstructure and tribological properties of composite coatings. The results show that the dilution rate decreases and the contact angle increases, respectively, as E decreases from 200.00 J/mm to 80.00 J/mm, which causes the decrease of the boding strength from 1.91 GPa to 0.39 GPa. The composite coatings contain the phases of γ-(Ni, Fe), Laves, TiB2, TiB, TiC, Ni3B, CrB4 and Cr23C6. As E decreases from 200.00 J/mm to 133.33 J/mm, the primary dendrite arm spacing (PDAS) and the Laves content of the composite coating decrease for the increase of cooling rate, leading to the increase of microhardness, the improvement of tribological properties and the change of wear mechanism from the severe multi-plastic deformation wear, adhesive wear and oxidative wear to the slight abrasive wear. However, as E decreases from 133.33 J/mm to 80.00 J/mm, for the weak Marangoni convection, TiB2 particles are prone to aggregate in the top of the composite coating which causes the increase of the PDAS and the Laves content, leading to the decrease of the microhardness and the degradation of tribological properties, and the wear mechanism change to the multi-plastic deformation wear and abrasive wear gradually.

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“…However, their effective use in high power laser applications has been limited to date. A number of authors [8][9] have described various reflective diffractive optics for use with carbon dioxide laser sources. The resulting beams were used in applications involving the soldering of several asymmetrically positioned joints on a circuit board, to the simultaneous welding and cutting of plastic foils.…”

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Use of a diffractive optic for high power laser cutting

Hilton

Lloyd

Tyrer

2015

Journal of Laser Applications

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There is a current interest in using laser cutting for nuclear decommissioning applications. The benefits of using lasers for this application include the high speeds available, the tolerance of the process, the lightness of the cutting head, the lack of a reaction force with the part being cut and the ease of automation of the laser cutting process. Of course laser cutting is a thermal process and a potential detriment, is that the residual laser beam, passing through the kerf, might damage or indeed set fire to, something positioned behind the part being cut. This paper describes the use of a diffractive optical element in the laser beam forming optics, designed to extend the depth of focus of the system, without increasing the focal length of the focusing optic. In this way, for cutting thick materials, the goal is to achieve the cutting performance of a long focal length lens, with the beam divergence of a short focal length lens. A design of diffractive optical element is presented, which when used with a 5kW fibre laser, in conjunction with a set of conventional beam forming optics, including a 250mm focal length focusing lens, is able to cut 40mm thick C-Mn steel plate at 50mm/min, while varying the nozzle tip to plate stand-off distance by 100mm. For the same laser power in the focusing beam, this performance is equaled by removing the diffractive optic and 250mm lens and replacing these with just a 500mm lens. However, the power density in the residual beam, when using the diffractive optical element, has been reduced by a factor four when compared to that from the optical arrangement using the 500mm lens. I. Introduction Since 2009, TWI Ltd. and others have demonstrated the potential of laser cutting for size reduction in nuclear decommissioning. [1-5]. In 2014, TWI used a 5kW fibre laser to size reduce radioactive Magnox type waste containers at a nuclear licensed site in the UK, [6]. Although the papers cited above demonstrate the benefits of laser cutting, such as ease of automation, high process speeds and lack of reaction force from the cutting tool on the material being cut, from the nuclear safety case point of view, there are some drawbacks to using laser beams for cutting. These include, but are not limited to, the effects of 'stray' beams that pass through the material being cut and impinge on something behind the cutting point, the temperature rise in the material being cut and the effects of the sparks generated in the laser cutting process. In addition, the amount of material removed from the cut kerf (hereafter in this paper referred to as dross), and fume generated and how this is dealt with, are also of concern. Hilton, [7] has addressed some of the safety case aspects described above, in particular the results, in terms of induced temperature rise and damage, of 'stray' laser beams of various power densities, impinging, either when stationary or when moving, on materials such as concrete, graphite and C-Mn and stainless steel.

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The use of holographic optical elements (HOE's) to investigate the use of a flat irradiance profile in the control of heat absorption in wire-fed laser cladding

Cited by 20 publications

References 18 publications

Using wire shaping techniques and holographic optics to optimize deposition characteristics in wire-based laser cladding

Using wire shaping techniques and holographic optics to optimize deposition characteristics in wire-based laser cladding

Effects of Process Parameters on Geometrical Characteristics, Microstructure and Tribological Properties of TiB2 Reinforced Inconel 718 Alloy Composite Coatings by Laser Cladding

Use of a diffractive optic for high power laser cutting

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