الفهرس 
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Abstract
Continuous wave diode pumped Nd:YAG laser was applied for welding of AISI 316L Stainless steel. Butt joint Sheets of 1.5mm thickness and 30mm width were joined together in a single pass without using filler material. Design of experiment is applied to investigate the effects of laser power, welding speed, and focal point position on fusion zone profile and the type of shield gas on the microstructure of the weld. Metallography, EDX analysis and mechanical properties including tensile strength and microhardness were investigated. The expected solidification mode according to WRC curve was Ferrite- Austenite (FA). The microstructure showed that most of the solidification was FA and the rest is Austenite- Ferrite (AF) mode of solidification. The depth of penetration is directly proportional with the laser power and inversely proportional to the welding speed. Maximum penetration depth was 753 µm at zero focal point and 602 µm at subsurface focal point. The tensile strength is directly proportional with the laser power. Maximum tensile strength is 632 MPa. Ductile fracture is revealed by SEM analysis. The average value of Microhardness of the weld when using nitrogen gas is 259 HV and by using argon gas is 275 HV while the average of the base metal reached 225 HV, this is because of the presence of different phases in weld metal from base metal.