Behrooz Beidokhti, Amin Ghorbani,
Volume 7, Issue 2 (1-2022)
Abstract
The present study investigated the effect of electrode composition and buffer layer on the microstructure and mechanical properties of H13 tool steel repair welds. Three specimens were welded applying two conditions; i.e. with and without stainless steel underlay. The microstructure of all weld metals contained the martensitic matrix with distributed chromium carbide precipitations. The microstructure of the underlay was a mixture of austenite and layers of ferrite with the skeletal morphology. The results showed that hardness of the welded substrates with underlay was higher than that of the specimens without underlay. This difference could be more than 240 HV. However, the highest hardness values were obtained in the heat affected zone of welds. The application of tough underlay improved the weld toughness and bending properties of the welded specimens. Also, it encouraged the ductile fracture mode in weldments. Also, the higher hardness of weld metal could be resulted from the application of buffer layer.
M. M. Taghvaei, H. Mostaan, A. Sonboli, H. R. Mansouri Gavari,
Volume 8, Issue 1 (8-2022)
Abstract
In this study, DIN 34CrAlNi7 Nitriding steel in two states before and after nitriding, were welded by tungsten-gas arc welding process using two types of fillers (ER309L and ER312). The aim of this research was to investigate the best conditions for welding (before or after nitriding) and also to choose the best filler metal. The microstructure of the joint was examined using an optical microscope. A tensile strength test was also used to evaluate the mechanical properties. Fracture surfaces were also studied using a scanning electron microscope (SEM). According to the results Welding of these steels with ER309L filler is allowed only in the pre-nitriding state. If the base metal is nitriding, due to microstructural changes in the weld metal, filler metal ER309L cannot be used. However, the results of samples welded with ER312 filler metal show that if the base metal mixing percentage is less than 30%, this filler can be used for welding base metals in both before and after nitriding.
M. Naseri Alenjagh, T. Saeid,
Volume 9, Issue 1 (5-2023)
Abstract
The purpose of this research is to investigate the change of rotational speed and traverse speed on the microstructure and mechanical properties of the joint in friction stir welding of aluminum 1050 and 316L stainless steel. For this purpose, the microstructure, thickness of intermetallic compounds, hardness and tensile test on the joint were investigated. The proper selection of welding parameters leads to the creation of a joint with suitable metallurgical and mechanical properties. In this research, two rotational speeds of 560 and 900 rpm and four traverse speeds of 60, 80, 100 and 125 mm/min were performed. The microstructure consisted of four areas of the base metal, heat affected zone, thermo-mechanical affected zone and stir zone. In all the samples, the stir zone (SZ) contained a recrystallization microstructure with fine equiaxed grains. According to the Energy dispersive X-ray Spectroscopy results, an IMC layer formed in the joint interface. The hardness of the stir zone in all samples was higher than the aluminum base metal due to the formation of recrystallization fine equiaxed grains and the presence of steel particles. The best sample in terms of mechanical properties, mocrostructure and joint quality was obtained in the conditions of rotation speed of 900 rpm and advance speed of 125 mm/min. The strength was equal to 84 MPa with 77% efficiency.
M. N. Sadraee Far, F. Kolahan,
Volume 9, Issue 2 (1-2024)
Abstract
In this study, we employed the active TIG method with ultrasonic vibration (UV) for welding 316L steel. Throughout the active tungsten inert gas (A-TIG) welding process, a high-frequency ultrasonic generator produced high-intensity acoustic waves at an optimal frequency of 20.3 kHz and a vibration amplitude of 8 micrometers. These waves were directed into the molten weld pool, covered by SiO2 nanoparticles serving as an activating flux. The effect of UV and nanoparticles on weld geometry and weld microstructure was analyzed and compared with conventional TIG welding proces. The results indicated that the use of nanopowder not only increased weld penetration by approximately 17.5% but also reduced the Weld Bead Width (WBW) by 28% compared to Conventional TIG. These values increased by 25% and decreased by 35%, respectively, in the presence of ultrasonic waves. Additionally, the introduction of nanomaterials into the molten pool led to finer grains. The ultrasonic waves played a crucial role in ensuring the uniform distribution of these nanomaterials in the melt, ultimately resulting in an enhanced microstructure of the weld.
P. Chamani, H. Sabet, M. Ghanbari Haghighi,
Volume 9, Issue 2 (1-2024)
Abstract
In this study the effect of rotational speed and tool angle parameters on the microstructure and mechanical properties of the AZ91/CP-Ti joint was investigated, for this reason the sheets with 4 x 26 x 100 mm dimensions were prepared and joint by FSW with different rotational speed (800, 1200 and 2500 rpm) and the tool angle (0.5, 1 and 3 degrees). After joining, the samples were cut and prepared for study of microstructural and mechanical properties. OM and SEM examination shows that the structure of AZ91/CP-Ti nugget zone includes alpha grains and the microstructure of the mix zone on the AZ91 side includes α-magnesium coaxial grains with Mg17Al12 intermetallic compounds. The results of the tensile test show that the maximum tensile strength value (160 MPa) related to the rotation speed of 2500 rpm and the tool angle of 1 degree. It was also determined that the rotation speed of 800 rpm was not suitable for joining of AZ91/CP-Ti. On the other hand, it was observed that by increasing the tool angle the work piece, initially leads to an increases the strength from 141 MPa to 160 MPa and then decreases to 132 MPa. the results of the Vickers hardness test show that the average of the nugget zone hardness was to 173, which is higher than the hardness of AZ91 alloy (61 Vickers) and near to the hardness of CP-Ti (167 Vickers).
Rouholah Ashiri, Amir Hosein Asadi, Massoud Goodarzi, Mohammad Saeed Shahriari,
Volume 9, Issue 2 (8-2026)
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.
