Journal of Welding Science and Technology of Iran

An experimental study on surface groove repair in pure magnesium using surface friction stir processing

A. Heidarzadeh

This study experimentally investigates the repair of surface grooves on pure magnesium samples using the surface friction stir processing (SFSP). Grooves with depths of 0.5, 1, and 1.5 mm were created and subsequently repaired under constant parameters of 1400 rpm rotational speed and 40 mm/min travel speed. The results revealed that the stir zone (SZ) exhibited fine equiaxed grains due to complete dynamic recrystallization, leading to significant improvements in tensile strength and hardness compared to the base metal. The highest ultimate tensile strength of 66.1 MPa and hardness of 60 HV were achieved in the 1 mm groove sample. Additionally, partial dynamic recrystallization was observed in the thermo-mechanically affected zone (TMAZ), and complete elimination of grooves was confirmed in all samples. These findings demonstrate that the SFSP is highly effective for localized repair and enhancement of mechanical properties in magnesium components, offering a promising solution to extend the service life of damaged magnesium parts.

Effect of GTAW repair welding and post-weld heat treatment on the microstructure and hardness of IN939 superalloy

R. Ashiri

Repair welding of nickel-based superalloy Inconel 939, which was under working conditions of 100,000 hours, was performed by gas tungsten arc welding using Inconel 617 filler metal. The main objective of this study is to investigate and analyze the challenges during welding such as irregular distribution of primary MC carbides and crack formation in the heat-affected zone, and also to investigate the effect of post-welding heat treatment cycle on the microstructure and hardness of different weld zones. During welding, a crack of 91 micrometers length was observed in the heat affected zone, which due to the presence of a liquation film and accumulation of carbides around the crack, the crack was categorized as a liquation crack. Then, due to post-welding heat treatment, improvement of microstructural characteristics and hardness of the weld zone, partial melted zone, and heat-affected zone was observed, which resulted in homogenization of the hardness profile of the weld. It was observed that post-welding heat treatment caused the crack formed during welding to grow and spread to reach a length of 386 micrometers, which was classified as a strain-aging crack due to its formation and growth during post-welding heat treatment.

Enhancing Hastelloy X weld properties using pulsed current GTAW process

Kh. Ranjbar

This study investigated the effects of pulsed current and constant current on the microstructure and mechanical properties of Hastelloy X superalloy welds produced by Gas Tungsten Arc Welding (GTAW), using ERNiCrMo-2 filler metal. Key microstructural parameters, such as elemental segregation, dendrite refinement, and weld metal uniformity, along with changes in weld strength and hardness, were examined and compared between the two welding modes. Microstructural evaluations were conducted using optical microscopy, Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDS), and X-ray Diffraction (XRD) for phase identification. Pulsed current welding resulted in a finer microstructure with more equiaxed dendrites, reduced elemental segregation, and a more uniform distribution of M₆C carbides. Furthermore, this process led to significant improvements in hardness, impact toughness, and tensile strength of the weld metal compared to constant current welding. Fracture analysis confirmed ductile fracture behavior in all specimens, consistent with the microstructural and mechanical findings. The results of this research highlight the importance of using pulsed current in GTAW as an effective method for controlling the microstructure and enhancing the mechanical properties of Hastelloy X alloy joints.

Mechanical and microstructural properties investigation of functionally graded Stellite6/17-4PH fabricated by direct laser deposition

R. Shoja Razavi

In this study, laser direct deposition was employed to fabricate a functionally graded transition between 17‑4PH stainless steel and Stellite 6. Specimens were designed and produced such that the chemical composition varied incrementally from 100% 17‑4PH to 100% Stellite 6, with each step involving a 25% decrease in the 17‑4PH content and a corresponding 25 % increase in Stellite 6. Microstructural evolution and elemental distribution were characterized by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS), while mechanical properties were assessed via Vickers microhardness testing and uniaxial tensile tests. The microstructural analysis revealed a needle‑like martensitic matrix in the substrate, which transformed into cellular dendrites upon reaching the 25% Stellite 6 layer. As the Stellite 6 fraction increased, along with corresponding rises in Cr and W content, grain boundaries broadened and carbides accumulated within interdendritic regions. At the 50% composition, oriented columnar dendrites became prominent, and at higher Stellite 6 levels the dendritic structure refined further, ultimately evolving into an equiaxed morphology. Microhardness measurements showed a continuous increase from approximately 300 HV in the 17‑4PH substrate to 490 HV in the pure Stellite 6 layer. Tensile testing demonstrated that both yield strength (σᵧ) and ultimate tensile strength (σᵤ) remained within 1102–1159 MPa across all compositions, with no evidence of brittle phases or manufacturing defects. Elongation increased from 7% in pure Stellite 6 to 19% in pure 17‑4PH, with the 50%–50% gradient exhibiting an optimal balance of strength and ductility (14.5% elongation).

Effect of FSSW parameters on the microstructure and mechanical properties of 5754 aluminum alloy

M.N. Yoozbashi

The friction stir spot welding (FSSW) process is a solid-state welding technique recognized as one of the most significant advancements in metal joining over the past decade. In this study, the effects of rotational speed and tool contact time, with a unique design different from previous research, on the microstructure and mechanical properties of 5754 series aluminum alloy were investigated. The workpiece was clamped using a specialized fixture on a radial drilling machine, and welding operations were performed using a FSSW machine at different rotational speeds and various tool contact times. Subsequently, the microstructure, microhardness, and tensile-shear strength of the welded spot region were evaluated. The results showed that increasing the tool rotational speed and prolonging the tool contact time led to an improvement of approximately 105% in the tensile-shear strength. According to statistical analyses, the factors of rotational speed and tool contact time significantly affected the shear strength with a confidence level greater than 95%; however, statistical analyses revealed different results regarding the relationship between rotational speed, contact time, and hardness.

Investigation of the effect of pulse frequency in gas tungsten arc welding (GTAW) of IN738LC nickel-based superalloy

R. Ashiri

The weldability of the superalloy Inconel 738LC is compromised by its susceptibility to heat-affected zone (HAZ) liquation cracking, a consequence of its high gamma-prime (γ') precipitate strength and the formation of low-melting-point eutectic phases. This study investigates the impact of Gas Tungsten Arc Welding (GTAW) current mode—comparing continuous current with pulsed current—on the microstructure, mechanical properties, and overall weldability of IN738LC. Through room-temperature tensile testing, Vickers hardness measurements, and microstructural analysis via optical and electron microscopy, it was demonstrated that pulsed current, particularly at higher frequencies, substantially mitigates liquation cracking and improves joint integrity. The pulsed technique introduces controlled thermal fluctuations that reduce the effective heat input, promoting a transition from columnar to equiaxed dendritic solidification, minimizing interdendritic segregation, and refining the distribution of MC carbides. Consequently, the weld metal exhibits enhanced tensile strength, ductility, and hardness. These findings establish pulsed GTAW as an effective strategy for suppressing cracking and improving the performance of IN738LC welded joints.

Experimental and numerical evaluation of groove depth effect on microstructural and mechanical behavior in repairing 7075 aluminum alloy by friction stir welding

M. Sajed

In this study, the Friction Stir Welding process was employed to repair artificial cracks and grooves in 7075 aluminum alloy. Samples with different groove depths (0.5, 1, 1.5, and 2 mm) were prepared and evaluated through experimental tests, metallographic analysis, tensile testing, and numerical simulation using Abaqus software. The results showed that the Friction Stir Welding successfully repaired the defects without creating voids or surface irregularities. Microstructural observations in the stir zone revealed that dynamic recrystallization led to the formation of fine and homogeneous grains, resulting in improved hardness and tensile strength. The specimen with a 1 mm groove depth exhibited the best mechanical performance, with a maximum hardness of approximately 109 HV and the highest tensile strength among all samples. Conversely, samples with 0.5 and 2 mm groove depths showed void formation and reduced strength due to insufficient or excessive heat input and uneven material flow. Both experimental and simulation results confirmed that a groove depth of 1 mm provides optimal conditions for defect repair in 7075 aluminum alloy.

Investigation of the effect of process temperature and time on the corrosion behavior of Al₀.₅CoCrFeMnTi₀.₅ high-entropy alloy coatings applied on plain carbon steel by diffusion bonding method

R. Dehmolaei

In this study, the effects of diffusion-bonding temperature and time on the microstructure and corrosion behavior of Al₀.₅CoCrFeMnTi₀.₅ high-entropy alloy coatings applied on A283 plain carbon steel were investigated. The coatings were produced by diffusion bonding using the spark plasma sintering method, in which high-entropy alloy powders were bonded to the substrate at temperatures of 850, 950, and 1050°C for holding times of 10, 15, and 20 minutes. Microstructural characterization performed by field-emission scanning electron microscopy (FESEM) revealed that increasing the diffusion-bonding temperature and time led to reduced porosity and enhanced coating densification. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests conducted in a 3.5 wt.% NaCl solution demonstrated that increasing the bonding temperature and time resulted in higher charge transfer resistance (Rct) and corrosion potential (Ecorr values, along with a decrease in corrosion current density (icorr). The coating produced at 1050°C with a holding time of 20 minutes exhibited the highest corrosion resistance. The improvement in corrosion performance was attributed to the formation of a uniform and adherent oxide film, which effectively inhibited the penetration of corrosive ions into the steel substrate.

Surface composite AA5083/Al12Mo fabricated via friction stir processing: Analysis of strengthening mechanisms, serrated flow delay, and corrosion resistance

H. Abdollah-Pour

In this study, an AA5083/Al12Mo surface composite containing approximately 10 vol.% of pre-synthesized molybdenum aluminide particles was fabricated using Friction Stir Processing (FSP) under optimized conditions, including six passes, a rotational speed of 1000 rpm, and a traverse speed of 52 mm/min. Multiple FSP passes reduced the particle size from about 20 µm to nearly 1.7 µm and improved their distribution uniformity, while simultaneously refining the matrix grains and enhancing the strain-hardening capability. These microstructural improvements led to a ~16% increase in tensile strength compared to the unreinforced FSPed alloy and ~20% relative to the as-received base metal, along with ~50% and ~63% hardness enhancement in the 4-pass and 6-pass samples, respectively. Quantitative analysis of the strengthening mechanisms revealed that strain hardening contributed the most to the overall strength increment, and the presence of reinforcing particles delayed the onset of the Portevin–Le Chatelier (PLC) serrated flow. Fractography indicated a mixed fracture mode consisting of particle fracture, particle–matrix decohesion, and matrix rupture. Furthermore, corrosion tests demonstrated a decrease in corrosion resistance, mainly due to the discontinuity of the protective aluminum oxide layer and the formation of defects at particle–matrix interfaces caused by severe plastic deformation.

Microstructural evolution of Inconel 738LC joints using two-step heating TLP bonding

B. Beidokhti

In this study, a novel two-step heating strategy was investigated for transient liquid-phase (TLP) bonding of the IN-738LC superalloy. The bonding process consisted of an initial heating at 1150 °C for 5 seconds, followed by holding at 1110–1130 °C for 3 to 40 minutes. The microstructural evolution during the process, as well as the interface morphology, was characterized and compared with conventional TLP joints. This approach significantly reduced the time required to complete isothermal solidification; the width of the central eutectic zone decreased from 45 µm at 3 minutes to 19 µm at 12 minutes, and the eutectic zone was completely eliminated after 40 minutes. Microstructural examinations revealed that the initial step of the two-step heating process produced a cellular–dendritic solidification interface, leading to a non-uniform distribution of porosity along the bond region. Subsequent homogenization removed boride precipitates and resulted in the formation of uniformly distributed γ′ precipitates similar to those in the base metal. These findings provide practical and microstructural insights into the influence of thermal profiles on interfacial evolution and offer a pathway for improving joint quality in nickel-based superalloys.

Effect of Degree of Dilution on the Adhesion and Continuity of The ER2209 Clad layer on AISI 1030 Cast Steel

H. Sabet

In the present study, AISI 1030 cast-steel samples were cladded using duplex stainless-steel wire ER2209 by the Gas Tungsten Arc Welding (GTAW) process under different preheating temperatures and varying numbers of passes. The degrre of dilution of the clad layers,affected by both of the preheating temperature and the number of passes—was calculated, and was evaluated its influence on the adhesion and bonding integrity of the ER2209 clad layer on the cast-steel substrate. The results showed that by increasing the number of clad layers led to a lower dilution in the samples. Furthermore, a rise in preheating temperature also contributed to an increase in dilution. Among all conditions, the three-pass cladded sample with a preheating temperature of 100 °C exhibited the highest dilution degree. Bending test results demonstrated that the bending angle increased by the number of clad passes. Macroscopic examination confirmed that complete interfacial continuity between the clad layer and the base metal. Phase analysis and microstructural observations revealed that the base metal consisted of approximately 80% ferrite and 20% pearlite; the heat-affected zone (HAZ) exhibited a ferrite–transformed pearlite structure with similar volume fractions; and the cladded samples in the final pass presented a duplex austenitic–ferritic structure with 10–20 Wt.% ferrite content. Microhardness test indicated that the two-pass cladded sample that preheated at 200 °C had the highest hardness value, up to 355 HV.

Effect of laser polishing on surface properties of Ti-6242 alloy fabricated by electron beam powder bed fusion method

M. Atapour

The Ti-6242 alloy is of particular significance in additive manufacturing due to its high thermal resistance. However, components fabricated from this alloy using the electron beam powder bed fusion (EB-PBF) process often exhibit poor surface quality, primarily resulting from the layer-by-layer fabrication nature and and the presence of partially melted powder particles. In this study, laser polishing was employed to enhance the surface characteristics of EB-PBF fabricated Ti-6242 specimens using three laser powers (195, 260, and 325 W) and two scanning speeds (4.5 and 3 mm/s). The effects of these parameters on surface roughness, microstructure, and mechanical properties were evaluated through surface profilometry, metallography, hardness, and wear tests. The results indicated that the average surface roughness decreased by up to 93%, from 9.36 µm to 0.61 µm. Moreover, the initial α and β phases transformed into a fine, martensitic α′ phase within the polished layer, leading to a 33% increase in hardness—from 380 to 506 HV—and a significant improvement in wear resistance. Consequently, optimal adjustment of laser polishing parameters can simultaneously reduce surface roughness and enhance the mechanical performance of Ti-6242 components.