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).
Rouholah Ashiri, Amir Hosein Asadi, Massoud Goodarzi, Mohammad Saeed Shahriari,
Volume 9, Issue 2 (Journal OF Welding Science and Technology 2026)
Abstract
Abstract
In this study, the effect of welding current on the repair welding behavior of the cobalt-based superalloy MAR-M509 was systematically investigated using four cobalt-based filler metals, namely HAYNES-188, HAYNES-25, MAR-M918, and FSX-414, in the Gas Tungsten Arc Welding (GTAW) process. Welding experiments were conducted at five current levels of 50, 60, 70, 80, and 90 A, and the influence of heat input on weld geometry, dilution, microstructural evolution, and hardness distribution was evaluated. Macroscopic observations revealed that insufficient heat input at low current levels resulted in lack of fusion (LOF) defects in some samples, whereas complete penetration was achieved for all filler metals at 80 and 90 A. Dilution generally increased with increasing welding current, indicating a greater contribution of the base metal to the fusion zone under higher heat input conditions. Microstructural investigations showed that increasing the welding current reduced the cooling rate and promoted dendritic growth, leading to increases in dendrite length, primary dendrite arm spacing (PDAS), and secondary dendrite arm spacing (SDAS). In addition, localized liquation phenomena were observed near the fusion boundary under high heat input conditions. Hardness profile analysis demonstrated that the heat-affected zone (HAZ) exhibited the highest sensitivity to thermal variations, and increasing welding current intensified hardness fluctuations due to carbide evolution and localized microstructural heterogeneity. Comparison of the four filler metals indicated that, although the overall trends were similar, the filler metal type significantly influenced dilution behavior, weld geometry, and solidification characteristics. Based on the combined evaluation of penetration, dilution, dendritic growth, and hardness distribution, a welding current of 80 A was identified as the optimum condition, providing the best balance between weld quality and microstructural stability in the repair welding of MAR-M509.
H.r. Pooreskandari, M. Goodarzi, R. Ashiri,
Volume 12, Issue 1 (Journal OF Welding Science and Technology 2026)
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 was characterized 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.
