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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.

Laser surface hardening (LSH) has become the most vital process in order to increase the hardness of a mild steel surface, especially to overcome the wear issues in machining parts, where mild steel was hugely applied. This is due to its advantages such as less air pollution, low cost of maintenance and easy to handle compared to other conventional surface hardening process. The laser surface hardening of mild steel has been performed using fibre laser machine which is having a maximum peak power of 30 Watt, with 1060 nm of wavelength above the surface of mild steel having dimension of 15 × 15 × 6 mm. The Vickers hardness test on the laser hardened surface of this metal were measured by a load of 0.5 kgf and 10 seconds dwell time for ten indention points, randomly. It was found that the highest average microhardness value was 281.72 HV on the surface of sample hardened by a laser power of 21 Watt and 40 mm/s scanning speed. Across the cross sectional area, the affected hardened depth was measured at 19 ± 2.5 µm from the surface. In this region, the fine martensitic grain structure was observed, which contributes to the higher microhardness value. Higher laser power produced higher surface hardness, meanwhile higher scanning speed lead to lower surface hardness.