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Article
Publication date: 10 June 2014

Linda Ke, Haihong Zhu, Jie Yin and Xinbing Wang

– The purpose of this paper is to report the influence of the peak laser power on laser micro sintering 4-μm nickel powder using Q-switched 1064-nm Nd:YAG laser.

Abstract

Purpose

The purpose of this paper is to report the influence of the peak laser power on laser micro sintering 4-μm nickel powder using Q-switched 1064-nm Nd:YAG laser.

Design/methodology/approach

Experimental study has been performed. Nickel powder with grain size of 4 μm has been utilized. A Q-switching duration of 20-25 μs and rate of 20-40 kHz have been used.

Findings

The peak power intensity is so high that the metal particles and molten pool are blown away, leading to laser micro sintering not being successfully proceeded. The scanning line obtained by continuous-wave (CW) laser looks like a rod owing to balling effect. Using a suitable peak power intensity, a good-shaped sintering line can be obtained because the plasma can protect the molten metal from oxidation, and improve the wettability of the system. In addition, the plasma flattening effect may also contribute to the form of the good-shaped sintering line in pulsed laser sintering regime.

Originality/value

The role of plasma induced by pulsed laser with high peak power intensity has been found during pulsed laser sintering under an ambient environment.

Details

Rapid Prototyping Journal, vol. 20 no. 4
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 30 May 2019

Pramod Kumar and Amar Nath Sinha

The present research work aims to study the effect of average beam power (laser process parameters) on the overlapping factor, depth of penetration (DOP), weld bead width…

Abstract

Purpose

The present research work aims to study the effect of average beam power (laser process parameters) on the overlapping factor, depth of penetration (DOP), weld bead width, fusion zone and heat affected zone (HAZ) in laser welding of 304L and st37 steel. Back side and top surface morphology of the welded joints have also been studied for varying average beam power.

Design/methodology/approach

Laser welding of austenitic stainless steel (304L) and carbon steel (st37) was carried out using Nd:YAG laser integrated with ABB IRB 1410 robot in pulse mode. The selection of laser process parameters was based on the specification of available laser welding machine. Dissimilar laser welding of 304L and st37 carbon steel for full depth of penetration have been performed, with varying average beam power (225-510W) and constant welding speed (5mm/s) and pulse width (5ms).

Findings

Recrystallized coarse grains were observed adjacent to the fusion zone and nucleated grains were seen away from the fusion zone towards carbon steel. Overlapping factor and HAZ width st37 side increases with increase in average beam power whereas top weld bead width increases first, attains maximum value and then subsequently decreases. Bottom weld bead width increases with increase in average beam power. The mechanical properties namely microhardness and tensile strength of the welded joints have been investigated with varying average beam power.

Originality/value

In the recent development of the automobile, power generation and petrochemical industries the application of dissimilar laser welding of austenitic stainless steel (304L) and carbon steel (st37) are gaining importance. Very limited work have been reported in pulsed Nd:YAG dissimilar laser welding of austenitic stainless steel (304L) and carbon steel (st37) for investigating the effect of laser process parameters on weld bead geometry, microstructural characterization and mechanical properties of the welded joint.

Details

World Journal of Engineering, vol. 16 no. 3
Type: Research Article
ISSN: 1708-5284

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Article
Publication date: 28 January 2020

Xingcheng Wang, Changjun Chen and Min Zhang

This paper aims to study the effect of laser energy on the formability, microstructure and mechanical properties of AZ61D alloy to assist systematic study of laser

Abstract

Purpose

This paper aims to study the effect of laser energy on the formability, microstructure and mechanical properties of AZ61D alloy to assist systematic study of laser additive manufacturing of magnesium alloys.

Design/methodology/approach

In this study, porous magnesium alloy samples were prepared by using different laser parameters. The changes of the formability and microstructure were observed by SEM, and the mechanical properties were tested. The above results were analyzed to obtain optimized laser parameters.

Findings

When the laser power is between 85 and 95 W (pulse width 3.0 ms, frequency 40 Hz), the surface morphology of the selective laser-melted (SLMed) porous samples are smooth and even. At 80 W, SLMed porous samples have a maximum relative density of 99.2 per cent. Because of the “solute capture” effect and the evaporization of magnesium, the fraction of ß-Mg17Al12 increases from 42.1 to 52.1 per cent when power rises from 80 to 105 W. The ultimate compressive strength of SLMed porous magnesium alloys is strengthened with the increase of laser power.

Originality/value

The effect of laser parameters on microstructure and mechanical properties of porous magnesium alloys prepared by SLM has not been reported.

Details

Rapid Prototyping Journal, vol. 26 no. 5
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 15 August 2016

Lei Yan, Xueyang Chen, Wei Li, Joseph Newkirk and Frank Liou

This paper aims to achieve Ti-6Al-4V from Ti, Al and V elemental powder blends using direct laser deposition (DLD) and to understand the effects of laser transverse speed…

Abstract

Purpose

This paper aims to achieve Ti-6Al-4V from Ti, Al and V elemental powder blends using direct laser deposition (DLD) and to understand the effects of laser transverse speed and laser power on the initial fabrication of deposit’s microstructure and Vickers hardness.

Design/methodology/approach

Two sets of powder blends with different weight percentage ratio for three elemental powder were used during DLD process. Five experiments with different processing parameters were performed to evaluate how microstructure and Vickers hardness change with laser power and laser transverse speed. Energy dispersive X-ray spectroscopy, optical microscopy and Vickers hardness test were used to analyze deposits’ properties.

Findings

This paper reveals that significant variance of elemental powder’s size and density would cause lack of weight percentage of certain elements in final part and using multiple coaxial powder nozzles design would be a solution. Also, higher laser power or slower laser transverse speed tend to benefit the formation of finer microstructures and increase Vickers hardness.

Originality/value

This paper demonstrates a new method to fabricate Ti-6Al-4V and gives out a possible weight percentage ratio 87:7:6 for Ti:Al:V at powder blends during DLD process. The relationship between microstructure and Vickers hardness with laser power and laser transverse speed would provide valuable reference for people working on tailoring material properties using elemental powder method.

Details

Rapid Prototyping Journal, vol. 22 no. 5
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 29 July 2014

Shouxu Wang, Li Feng, Yuanming Chen, Wei He, Zhihua Tao, Shijing Chen and Huan Xu

The purpose of this paper is to form good cutting qualities in glass-epoxy material for opening flexible areas of rigid-flex printed circuit boards (PCB) by ultraviolet…

Abstract

Purpose

The purpose of this paper is to form good cutting qualities in glass-epoxy material for opening flexible areas of rigid-flex printed circuit boards (PCB) by ultraviolet (UV) laser cutting.

Design/methodology/approach

The cut width and cut depth of glass-epoxy materials were both observed to evaluate their cutting qualities. The heat affected zone (HAZ) of the glass-epoxy material was also investigated after UV laser cutting. The relationships between the cut width and the parameters of various factors were analyzed using an orthogonal experimental design.

Findings

The cut width of the glass-epoxy material gradually increased with the increment of the laser power and Z-axis height, while cutting speed and laser frequency had less effect on the cut width. Optimal parameters of the UV laser process for cutting glass-epoxy material were obtained and included a laser power of 6W, a cutting speed of 170 mm/s, a laser frequency of 50 kHz and a Z-axis height of 0.6 mm, resulting in an average cut width of 25 μm and small HAZ.

Originality/value

Flexible areas of rigid-flex PCBs are in good agreement with the cutting qualities of the UV laser. The use of a UV laser process could have important potential for cutting glass-epoxy materials used in the PCB industry.

Details

Circuit World, vol. 40 no. 3
Type: Research Article
ISSN: 0305-6120

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Article
Publication date: 12 November 2020

Abid Ullah, HengAn Wu, Asif Ur Rehman, YinBo Zhu, Tingting Liu and Kai Zhang

The purpose of this paper is to eliminate Part defects and enrich additive manufacturing of ceramics. Laser powder bed fusion (L-PBF) experiments were carried to…

Abstract

Purpose

The purpose of this paper is to eliminate Part defects and enrich additive manufacturing of ceramics. Laser powder bed fusion (L-PBF) experiments were carried to investigate the effects of laser parameters and selective oxidation of Titanium (mixed with TiO2) on the microstructure, surface quality and melting state of Titania. The causes of several L-PBF parts defects were thoroughly analyzed.

Design/methodology/approach

Laser power and scanning speed were varied within a specific range (50–125 W and 170–200 mm/s, respectively). Furthermore, varying loads of Ti (1%, 3%, 5% and 15%) were mixed with TiO2, which was selectively oxidized with laser beam in the presence of oxygen environment.

Findings

Part defects such as cracks, pores and uneven grains growth were widely reduced in TiO2 L-PBF specimens. Increasing the laser power and decreasing the scanning speed shown significant improvements in the surface morphology of TiO2 ceramics. The amount of Ti material was fully melted and simultaneously changed into TiO2 by the application of the laser beam. The selective oxidation of Ti material also improved the melting condition, microstructure and surface quality of the specimens.

Originality/value

TiO2 ceramic specimens were produced through L-PBF process. Increasing the laser power and decreasing the scanning speed is an effective way to sufficiently melt the powders and reduce parts defects. Selective oxidation of Ti by a high power laser beam approach was used to improve the manufacturability of TiO2 specimens.

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Article
Publication date: 15 June 2010

Kamran Mumtaz and Neil Hopkinson

The purpose of this paper is to investigate the selective laser melting (SLM) of Inconel 625 using pulse shape control to vary the energy distribution within a single laser

Abstract

Purpose

The purpose of this paper is to investigate the selective laser melting (SLM) of Inconel 625 using pulse shape control to vary the energy distribution within a single laser pulse. It aims to discuss the effectiveness of pulse shaping, including potential benefits for use within SLM.

Design/methodology/approach

Laser parameters were varied in order to identify optimal parameters that produced thin wall parts with a low surface roughness without the use of pulse shape control. Pulse shape control was then employed to provide gradual heating or a prolonged cooling effect with a variety of peak power/pulse energy combinations. Properties of pulse shaped and nonpulse shaped parts were compared, with particular attention focused on part surface roughness and width.

Findings

High peak powers tended to reduce top surface roughness and reduce side roughness as recoil pressures flatten out the melt pool and inhibit melt pool instabilities from developing. Ramp up energy distribution can reduce the maximum peak power required to melt material and reduce material spatter generation during processing due to a localized preheating effect. Ramp down energy distribution prolonged melt pool solidification allowing more time for molten material to redistribute, subsequently reducing the top surface roughness of parts. However, larger melt pools and longer solidification times increased the side roughness of parts due to a possible lateral expulsion of material from the melt pool.

Originality/value

This paper is the first of its kind to employ laser pulse shape control during SLM to process material from powder bed. It is a useful aid in unveiling relationships between laser energy distribution and the formation of parts.

Details

Rapid Prototyping Journal, vol. 16 no. 4
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 27 November 2018

Mahmoud Elsayed, Mootaz Ghazy, Yehia Youssef and Khamis Essa

Ti6Al4V alloy has received a great deal of attention in medical applications due to its biomechanical compatibility. However, the human bone stiffness is between 10 and 30…

Abstract

Purpose

Ti6Al4V alloy has received a great deal of attention in medical applications due to its biomechanical compatibility. However, the human bone stiffness is between 10 and 30 GPa while solid Ti6Al4V is several times stiffer, which would cause stress shielding with the surrounding bone, which can lead to implant and/or the surrounding bone’s failure.

Design/methodology/approach

In this work, the effect of selective laser melting (SLM) process parameters on the characteristics of Ti6Al4V samples, such as porosity level, surface roughness, elastic modulus and compressive strength (UCS), has been investigated using response surface method. The examined ranges of process parameters were 35-50 W for laser power, 100-400 mm/s for scan speed and 35-120 µm for hatch spacing. The process parameters have been optimized to obtain structures with properties very close to that in human bones.

Findings

The results showed that the porosity percentage of a SLM component could be increased by reducing the laser power and/or increasing the scan speed and hatch spacing. It was also shown that there was a reverse relationship between the porosity level and both the modulus of elasticity and UCS of the SLM part. In addition, the increased laser power was resulted into a substantial decrease of the surface roughness of SLM parts. Results from the optimization study revealed that the interaction between laser process parameters (i.e. laser power, laser speed, and the laser spacing) have the most significant influence on the mechanical properties of fabricated samples. The optimized values for the manufacturing of medical implants were 49 W, 400 mm/s and 99 µm for the laser power, laser speed and laser spacing, respectively. The corresponding porosity, surface roughness, modulus of elasticity and UCS were 23.62 per cent, 8.68 µm, 30 GPa and 522 MPa, respectively.

Originality/value

Previous investigations related to additive manufacturing of Ti alloys have focused on producing fully dense and high-integrity structures. There is a clear gap in literature regarding the simultaneous enhancement and adjustment of pore fraction, surface and mechanical properties of Ti6Al4V SLM components toward biomedical implants. This was the objective of the current study.

Details

Rapid Prototyping Journal, vol. 25 no. 3
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 9 November 2018

Jelena Stašić and Dušan Božić

This paper aims to report the production of 316L-1 Wt.% NiB cubes by using the selective laser melting (SLM) process. The laser used was pulsed, millisecond Nd:YAG system…

Abstract

Purpose

This paper aims to report the production of 316L-1 Wt.% NiB cubes by using the selective laser melting (SLM) process. The laser used was pulsed, millisecond Nd:YAG system with maximum average power 100 W.

Design/methodology/approach

Densification under different processing conditions (pulse energy, average laser power, laser scan speed, powder layer thickness, pulse frequency) was investigated. Morphology, macro and microstructure of laser melted samples were characterized by digital camera images and by scanning electron microscope. Density of the cubes was determined by Archimedes method in water. Vickers microhardness of samples was determined under the load of 25 g. Corrosion behavior of 316L and 316L-NiB samples was conducted in 5 per cent HCl solution at the testing temperature of 20°C during 240 h.

Findings

Using laser power of ∼60-70 W, lower beam overlap and powder layer thickness of 200 µm, 3D cubical samples were obtained with significant balling in individual layers and an overall porosity being around 30 per cent. By increasing laser power to ∼80 W, with higher beam overlap and lower powder layer thickness of 100 µm, SLM parts with no balling and the presence of small pores of up to 4 per cent (20 Hz) and 9 per cent (40 Hz) were obtained. With further increase of laser power to 90 W, overall porosity rose to around 12 per cent. The addition of 1 Wt.% NiB to stainless steel negligibly lowered its corrosion resistance in 5 per cent HCl solution.

Originality/value

A part from 316L stainless steel with balling-free structure and good density was successfully obtained through pulsed-SLM process with the aid of 1 Wt.% of NiB addition. Aside from significant influence on the improved structure of cubes, NiB had a favorable effect on microhardness values while practically not affecting the corrosion resistivity of the base material in an aggressive surrounding.

Details

Rapid Prototyping Journal, vol. 25 no. 1
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 11 January 2013

Haihong Zhu, Linda Ke, Wenjuan Lei, Cheng Dai and Baijin Chen

The purpose of this paper is to investigate the effect of the Q‐switching parameters on the sintering behavior of laser micro sintering Cu‐based metal powder, using…

Abstract

Purpose

The purpose of this paper is to investigate the effect of the Q‐switching parameters on the sintering behavior of laser micro sintering Cu‐based metal powder, using Q‐switched 1064 nm Nd‐YAG laser.

Design/methodology/approach

An experimental study has been performed. Metal powder mixture with Cu and Cu‐P alloy powders has been utilized. Q‐switching duration of 15 μs∼25 μs, rate of 25 kHz∼45 kHz have been used.

Findings

The results show that as the Q‐switching rate and duration increases, the peak laser power decreases and the densification enhances. However, an optimal peak laser power exists and if the peak laser power is too low, the density of the sample is also low. The densification regime of laser micro‐sintering is not only caused by the liquid phase filling the pores, but is also caused by the Cu powder migrating and by coalescence, e.g. including initial stage and intermediate stage of the traditional furnace liquid phase sintering. However, the degree of these stages depends on the peak power and input laser energy.

Originality/value

The effect of the Q‐switching parameters on sintering behavior of laser micro sintering Cu‐based metal powder using Q‐switched 1064 nm Nd‐YAG laser has been obtained. It is found that the densification behavior is Q‐switching parameters dependent, although the average laser power is same. The densification regime of laser micro‐sintering includes initial stage and intermediate stage of the traditional furnace liquid phase sintering, but the degree is Q‐switching parameters dependent.

Details

Rapid Prototyping Journal, vol. 19 no. 1
Type: Research Article
ISSN: 1355-2546

Keywords

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