**3.2 Selective laser melting (SLM)**

SLM is a powder bed fusion process [26]. It uses a laser beam which melts and then fuses the metal powders together as a thin layer of powder is deposited over the substrate plate then the laser beam fuses the powder particles selectively as dictated by the computer aided design data. Process parameters must be taken into consideration in order to fabricate a defect-free-part [27, 28]. The process parameters are laser power, laser scan speed, hatch distance, hatch overlaps, hatch style etc. and these parameters all affect the mechanical properties and influences the microstructures of the parts [29, 30].
