Showing 4 results for goodarzi
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.
Hamidreza Pooreskandari, Masoud Goodarzi, Rouholah Ashiri,
Volume 9, Issue 2 (Journal OF Welding Science and Technology 2026)
Abstract
The superalloy Inconel 738LC is considered one of the most challenging alloys in welding processes due to its widespread use in gas turbine blades and its high microstructural sensitivity to heat. The most significant limitation in welding this alloy is its high susceptibility to hot cracking in the heat-affected zone (HAZ), which arises from the formation of intergranular liquid films during the welding thermal cycle. In this study, the effect of activated tungsten inert gas (A-GTAW) welding on the behavior of the heat-affected zone, liquid film thickness, and hot cracking susceptibility in Inconel 738LC superalloy was investigated. For this purpose, specimens were welded with various fluxes under approximately constant heat input conditions, and the effect of the active flux on weld geometry, HAZ width, and liquid film thickness was evaluated. The results showed that the use of active flux, by inducing arc constriction and altering the molten metal flow pattern due to the reverse Marangoni effect, leads to more effective heat transfer into the depth of the workpiece and reduces lateral heat dissipation. This resulted in a reduction of HAZ width and a decrease in liquid film thickness in some specimens. It was also found that cracking behavior is a function of the interaction between liquid film thickness and the contraction stress of the weld pool. In the flux-free specimen, despite the formation of a greater number of liquid films, none developed into hot cracks, which was attributed to greater stability of the liquid films and their ability to fill discontinuities. Overall, the results of this study indicate that the A-GTAW process can influence hot cracking susceptibility in Inconel 738LC superalloy by controlling the heat transfer pattern and liquid film formation conditions.
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.
