S teels with martensitic microstructure (low carbon) and high creep resistance can be used at high temperatures for a long period of time. One of the potential applications of these materials is thermal and nuclear power plants. Over the years, the demand on the service temperature level in these plants have increased. As a result, studies on the development of new steel-based materials with enhanced creep and corrosion resistance have soared. The graph shown in Fig. 1 shows the need for service temperatures and pressures depending on years. Steels with 9-12% Cr content have been started to be used in these applications since 1950s. These steels

In this study, a 6 mm-thick 6061 T6 aluminum alloy was welded using fiber laser welding, and its mechanical and metallurgical properties were investigated. Full penetration autogenous welds were made at a constant laser power of 4.95 kW using a continuous-wave fiber laser and focal positions of −4 mm. In addition, the shielding gas content was changed for weldments welded at different travel speeds (mm s−1). Accordingly, welding speeds were 50, 40, 35, 25, and 20 mm s−1, and the shielding gas contents were 100% argon (Ar), 10% helium (He) + 90% Ar, 30% He + 70% Ar, 50% He + 50% Ar, and 75% He + 25% Ar. Then, macro and micro images were taken, and some mechanical properties (hardness, tensile test, and bending test) were examined. As a result, the change in shielding gas content and welding speed has provided significant variations in the welding joints. Decreases in mechanical properties were detected due to the coarsening of the precipitates. On the other hand, the narrowness of the weld seam and HAZ obtained in laser welding, compared to traditional welding methods, minimizes this disadvantage.

In this study, 6 mm thick plates of Al 6061 T6 alloy are joined by laser welding at four welding speeds (40 mm × s-1, 35 mm × s-1, 25 mm × s-1, and 20 mm × s-1). The welded joints are made using a 4000 W fiber laser welding machine. The effect of laser welding speed on the pores formed in the weld seam was investigated. In this manner, it was found that with a change in laser welding speed the amount of pores formed in the structure also changed. In addition, after the welding process, macroscopic examinations, tensile tests and the hardness tests were made. As a result of the experiments performed, it was determined that, the laser welding speed was highly effective for pore formation.

In this study, EN AW 6061-T6 Al alloy having a thickness of 6 mm was joined with a 5000 W fiber laser welding machine using different welding speeds (20, 25, and 35 mm/s) and shielding gas compositions (100% Ar, % 50 Ar + % 50 He, % 25 Ar + 75 He). In order to reduce the strength decrease in the weld zone, 5356 filler metal with a diameter of 1.2 mm was used with the cold wire feeding method at a constant speed of 2 m/min. Structural analyses of the joints were performed by macroscopic and microscopic examination, and hardness profiles and strength values of the joints were determined by mechanical tests. The findings showed that (i) the width of the seam increased due to the increase in the amount of He in the gas composition, and the number of pores decreased accordingly, (ii) although no significant change was observed in the hardness profiles, the highest tensile strength value (242 MPa) was obtained using a gas composition of 50% He + 50% Ar and welding speed of 20 mm/s, (iii) shear failure was the dominant fracture, and the porosities played a decisive role in the fracture.