Microstructure Of Dissimilar Weld Joints Research Articles

Effect of Welding Parameters on Dissimilar Pulsed Laser Joint between Nickel-Based Alloy Hastelloy X and Austenitic Stainless Steel AISI 304L

This paper investigates the strength and microstructure of dissimilar weld joints between Hastelloy X, which is a nickel-based superalloy, and austenitic stainless steel 304L. Nd-YAG solid-state pulsed laser is used to perform the welding between these two alloys. Two pieces of Hastelloy X and AISI 304L sheets of 1 mm thickness, are placed edge to edge to form a butt welding configuration with each other and are welded using a pulsed laser beam with a maximum power of 400 watts. The effect of welding speed, laser power and pulse width on the strength of the joint, were investigated by changing mentioned parameters values, while the laser beam frequency and the protective gas flow rate were kept constant. Then, test samples are produced to conduct uniaxial tensile tests at room temperature. Results show that the highest-quality dissimilar joint can be found by optimizing the welding power, beam pulse width, and welding speed.

Numerical and Experimental Investigation of the Heat Input Effect on the Mechanical Properties and Microstructure of Dissimilar Weld Joints of 690-MPa QT and TMCP Steel

The study evaluates numerically and experimentally the effect of welding heat input parameters on the microstructure and hardness of the heat-affected zone (HAZ) of quenched and tempered (QT) and thermo-mechanically controlled process (TMCP) 690-MPa high-strength steel. Numerical analyses and experimental comparisons were applied using three heat input values (10, 14, and 17 kJ/cm) in order to predict the thermal fields during welding. Experimental analysis was carried out of the microstructure and microhardness behavior in different HAZ areas. The numerical values indicate that the maximum respective values of temperature measured in QT steel and TMCP steel were about 1300 and 1200 °C for a heat input of 10 kJ/cm, 1400 and 1300 °C for a heat input of 14 kJ/cm, and 1600 and 1450 °C for a heat input of 17 kJ/cm. The cooling times resulted, for a heat input of 10 kJ/cm, in numerical t8/5 (14.5 s) and experimental (18.84 s) increases in hardness in the coarse-grain heat-affected zone (CGHAZ) of the QT steel (317 HV0.1), due to the formation of bainite and lath martensite structures with grain growth. Decreased hardness in the CGHAZ of TMCP steel (240 HV0.1) was caused by primary recrystallization of the microstructure and the formation of more equilibrium products of austenite decomposition. Increasing the heat input (14 to 17 kJ/cm) led to numerical t8/5 (29 s) and experimental (36 s) decreases in hardness in the CGHAZ of QT steel (270 HV0.1) due to the full austenite (thermal weld cycle), and maintained the relative value of TMCP steel (235 HV0.1).