M. Alimadadi, M. Goodarzi, S.m.a. Boutorabi,
Volume 7, Issue 1 (Journal OF Welding Science and Technology 2021)
Abstract
This present study aimed to create an Al6061-St52 dissimilar joint and investigate the effect of the transverse speed by the friction stir welding process. Welding aluminum to steel is rugged by fusion methods because of the formation of brittle intermetallic compounds (IMCs). Therefore, to designate optimal parameters, acceptable IMC thickness, and mechanical properties determined. This research carried out different three transverse speeds of 16, 40 and 85 mm/min (with a constant pin offset of 0.2 mm). Geometry of tool's pin radius and height is 4mm and 1.8mm, respectively. In the transverse speed parameter, the highest ultimate tensile strength (UTS) of 200 MPa was obtained at 85 mm/min. According to the Energy Dispersive X-ray Spectroscopy results, an IMC layer formed in the joint interface. The heat input rate was calculated to designate the optimal parameters. In tensile specimens, fracture mainly occurred in the joints and within the aluminum stir zone due to the combination of thick IMC layer and steel fragments, respectively. The micro-hardness measurement results showed that at (85 mm/min) the hardness values were HV 75 in the aluminum stir zone and HV 315 in the AS vicinity of the interface region. This hardness value is much higher than the base metals (Aluminum base metal is an average of HV 53 and an average steel base metal of HV 245).
Hamidreza Pooreskandari, Masoud Goodarzi, Rouholah Ashiri,
Volume 9, Issue 2 (Journal OF Welding Science and Technology 2025)
Abstract
Nickel-based superalloys are among the most critical materials used in high-temperature components of gas turbines, where their replacement costs and potential turbine damage necessitate effective protection and repair strategies. Optimizing repair methods to enhance efficiency and reduce costs has therefore been a continuous focus. The aim of this study is to improve the repair process of Inconel 738LC superalloy by reducing the susceptibility to liquation cracking. Activated tungsten inert gas (A-TIG) welding was performed on Inconel 738LC using a welding current of 60 A. Titanium dioxide (TiO₂) powder was employed as an activating flux, and weldments with four flux concentrations were examined. The microstructure w:::::as char:::::acterized using optical microscopy and scanning electron microscopy. The results revealed that flux concentration had a significant influence on penetration depth, with a concentration of 1 g/mL producing the maximum effect. At this concentration, weld penetration increased by 68% and weld pool volume by 63%, while the heat-affected zone width decreased by 12%. Arc imaging and quantitative/qualitative analysis demonstrated a constricted and focused plasma arc column in the presence of TiO₂ flux. Microstructural examinations further revealed suppression of columnar dendrite growth. It was found that TiO₂ flux enhances weld penetration and pool volume by constricting the arc and activating a reversed Marangoni flow, while simultaneously reducing HAZ width. However, the increased weld pool volume also intensified contraction stresses, leading to liquation cracking in the weld with the largest pool volume.
