Journal of Welding Science

The aim of the present study is to investigate the mechanical and microstructural properties of 1.7225 steel in laser welding process using Nd:YAG pulsed laser device and then to determine the optimal focal length relative to the part in the welding area. After welding, microstructural characterization, microhardness and tensile tests were performed. Evaluations showed that the optimal focal length for welding of steel sheet 1.7225 with a thickness of 1 mm, it was about 9 mm and the focus was 1 mm below the surface of the part. Due to the high thermal concentration and cooling rate in laser welding, a completely martensitic microstructure has been observed in the molten and heat-affected regions of all specimens. In this alloy, the hardness of the base metal is 310±10 HV. After welding, the hardness of the sample with the optimal focal length   has reached 625±10 HV in the heat affected zone and 730±10 HV in the melting zone. Also, the results of tensile test showed that the tensile properties of the sample with the optimal focal length were almost similar to the base steel and fracture was observed in the base steel region.
 

Inconel 713LC super alloy is one of the most widely used high-temperature alloys. Due to the high level of gamma prime phase caused by Ti and Al alloy more than a critical value, this alloy is considered as one of the non-weldable alloys. One of the basic repair methods of this series of superalloys is laser cladding methods. In this research, the IN713LC  substrate was reconstructed with Inconel 625 powder by a direct laser deposition system. To characterize, optical and electron microscopy tests, porosity measurement, and XRD were carried out; The results showed that the R (growth rate of the dendrite tip) increases at high speeds of laser cladding; as a result, the G/R (combined solidification point) ratio decreases, and the structure tends towards the coaxial dendritic direction. For this reason, by increasing the speed of laser scanning from 4 to 6 mm/s, the coaxial dendritic structure increases. The hardness measurement results indicate a decrease in the hardness up to the junction area from 430 to 370 Vickers and fluctuations of about 50 Vickers. Due to the high solidification speed, the average distance between the secondary dendritic arm space was 0.8 at the bottom, 1.01 in the middle, and 1.75 micrometers at the top of the sample. Due to the high cooling speed, only carbides and lava phases are formed. Also, the porosity measurement results of the cladding indicate a maximum porosity of 0.1 percent.