Effect of laser surface modification (LSM) on laser energy absorption for laser brazing

Since the development of the laser in the 1960s a rapid development of research interests in science and technology took place. Since then, the need of laser application in industrials such as automotive, aerospace and electronics is increasing because of several advantages like automation worthiness, noncontact processing and product quality improvement. In this present study, the effect of Laser Surface Modification (LSM) on pure copper plate towards the laser energy absorption during indirect laser brazing process was studied. The laser brazing experiment was conducted inside a chamber under controlled vacuum pressure with 400Pa and irradiated with constant 140 Watt laser power. The defocusing features for laser brazing was used in order to find better focal position. Accordingly, the focal length for this laser brazing experiment was set to the focus point at 124 mm from the focal plane. Meanwhile, during LSM process, laser parameters such as laser scanning speed and focus length have been kept constant throughout the surface modification process. Yet, the laser power and laser frequency have been varied from 9 Watt to 27 Watt and 10 kHz to 80 kHz respectively. Apparently, surface roughness due to surface removal and oxide layer formation were presented during LSM process. These two surface integrities were found to be the factors of increasing laser energy absorption. It was discovered that an increase in surface roughness and oxide layer formation can absorb more laser energy which then results an increase in brazing temperature during laser brazing. This is because, increasing surface roughness will scatter the laser energy over a larger surface area, multiply the reflections in the surface irregularities while the oxide layer will enhance the interference phenomena of laser energy occurring inside the oxide layer. Both mechanisms increase laser energy absorptivity during laser brazing which results a high brazing temperature

Enhancement of laser heating process by laser surface modification on titanium alloy

Titanium alloys are widely utilized in laser heating applications. However, it has poor optical properties due to low laser energy absorption. Nevertheless, a higher energy absorption can be realized by modifying the surface profile through increasing the surface roughness. In this present work, the laser surface modification (LSM) process was carried out to increase the roughness on surface of Ti6Al4V titanium alloy. Subsequently, the surface characterization and surface roughness were analysed by using the 3D optical microscope. The effect of laser power on the increment of surface roughness was investigated. It was revealed that an increase in laser power during LSM process could increase the surface roughness. The result shows that, the surface roughness of titanium alloy increased 27 times when modified with the highest laser power (27W) compared to the gritted surface. Furthermore, the modified surface by LSM will be heated using laser radiation in order to analyse the effect of surface roughness towards laser heating temperature. Depending on the value of the power during laser heating, the maximum temperature measured could be increased 27% corresponding to a gritted flat reference surface

Influence of laser surface texturing (LST) parameters on the surface characteristics of Ti6al4v and the effects thereof on laser heating

With rapid growth in laser-based manufacturing technologies, laser brazing has attracted significant attention in various industries such as automotive, biomedical and aerospace. Material heating in laser brazing is one of the factors to ensure maximum reaction between the filler and the base metal. During laser heating the energy needed to melt the filler is also dependent on the laser-material interaction, so in this work the effect of laser surface texturing (LST) parameters such as power, pulse frequency and scan speed on the surface morphology and roughness properties of Ti6Al4V were investigated using a fibre laser. It was found that an increase in laser power accompanied by a decrease in frequency and scan speed could increase the surface roughness. Additionally, the effect of surface roughness towards laser heating temperature was also studied with a fibre laser. When laser beam radiates a rougher surface the maximum temperature attained is 41.4% higher compared to a polished surface. This was mainly due to the laser energy scattering over a larger and rougher surface area causing amplification of the energy absorption in the form of temperature rise

Effect of laser surface modification on SS316L surface roughness and laser heating temperature

Nowadays, stainless steel is widely used in laser processing applications, including laser heating, laser brazing, and laser welding. However, it has poor optical properties due to low laser energy absorption. However, this could be improved with the aid of laser surface modification (LSM). The significance of this work is to examine the influence of LSM laser power on the surface roughness of 316L stainless steel samples. First, the LSM laser power was varied from 15 to 27 W. Then, the surface topography and variation of the surface roughness values were examined by using a 3D optical microscope. Furthermore, the modified surface by LSM will be heated using laser radiation in order to analyze the effect of surface roughness towards laser heating temperature. The result revealed that as the LSM power increased, thereby resulting in an increase of surface roughness. The highest LSM laser power (27 W) produced the highest surface roughness with 28.98 μm. Experimental results illustrate that the heating temperature were increased 36%, corresponding to a polished flat reference surface, which indicates the increment in energy absorptivity

Effect of laser loop on surface morphology of copper substrate and wettability of solder joint

The effect of different laser loop parameter on the geometry of micro-groove pattern on copper substrate and its effect on the wettability was investigated. The micro-grooves pattern was fabricated on the copper surface through laser surface texturing process. 3D measuring laser microscope and contact angle measurement test was conducted to measure the geometry of the micro-grooves pattern and wettability of the solder joint respectively. The results showed that the improvement in laser loop parameter increased the depth of the micro-grooves due to the more exposed time which allows more material ablation. It also showed that the contact angle of textured substrate is smaller than the untextured substrate which results in better wettability

Laser surface modification of duplex stainless steel 2205 to modify the surface roughness

Laser surface modification is an emerging process that can produce texture on a work surface and effectively enhance surface topography while altering surface roughness. Laser surface modification is a sensitive process that depends on various laser processing parameters such as power, scanning speed, hatching distance. The significance of this work is to examine the influence of hatching distance on the surface characteristic of 2205 duplex stainless steel samples. The surface transformation and variation of the surface roughness properties of the materials were examined. The hatching distance was varied from 0.1 to 0.005 mm. Results indicate that, as the hatch spacing decreases, the overlap of laser track increases, thereby resulting in a decrease of surface roughness. Meanwhile, with the increase of hatch distance, the clear overlay tracks were transformed to irregular wavy surface. The best hatch distance parameter obtained was 100 μm that resulted in the highest roughness of 8.45 μm. Experimental results illustrate that, when the optimum hatch distance of 100 μm was adopted, the polished smooth surface of 2205 duplex stainless steel with initial average roughness value of 0.19 μm increased by 42 times of the polished surface roughness. A strong correlation between hatching distance and roughness was established in 2205 duplex stainless steel. High depth of the altered surface topography and increased roughness were linked to higher levels of hatching distance