Journal of Welding Science

Welding is one of the methods of surface repair of cast irons. In this study, surface repair of gray cast iron was first performed by gas metal arc welding method with ER70S-6 welding wire under inter-pulse current, heat input of 393 J/mm and dilution of 17%. Also, to compare the results, two samples were welded with ENi-CI and E6013 covered electrodes. Microstructural studies showed that the microstructure of the interface of the sample is composed of martensite with fine lathes and upper bainite. Despite the presence of cementite (Fe₃C) next to alpha iron (α-Fe) in the interface area, the formation of incomplete mixing zone with bainite lathes in the ferrite zone has led to increased toughness and prevented crack formation. The hardness of the ER70S-6 sample was similar to that of the E6013 sample at the interface, at about 809 Vickers, which is 334 Vickers higher than the hardness of the ENi-CI sample. The results of the open circuit potential and potentiodynamic polarization tests showed that the ER70-CI sample, with a corrosion potential and current of -653 mV and 6.8 μA/cm², had a higher polarization resistance and was more resistant to galvanic corrosion than the ENi-CI sample (-622 mV and 8.9 μA/cm²).

In this study, the metallurgical and mechanical properties of the interface obtained by explosive welding of 8-92 phosphor bronze to St37 carbon steel were investigated. The effects of explosive welding parameters such as explosive charge amount and stand-off distance on the shape and microstructure of the interface, mechanical properties and corrosion behavior were investigated. The results showed that with increasing stand-off distance and explosive charge amount, the velocity and angle of impact increased, and this phenomenon led to the interface transforming from a smooth to a wavy state and resulting in melted and separated regions. The results obtained from scanning electron microscope (SEM) images showed that with increasing stand-off distance and explosive charge amount and consequently increasing impact velocity, the length and height of the waves created at the interface increased. Energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis showed that no intermetallic compounds were formed at the joint interface. The results of the microhardness test also indicated that the hardness around the joint interface increased by 25% due to plastic deformation and work hardening caused by the intense impact of the base and flying plates. By performing shear strength tests, it was found that in all samples, failure occurred in the phosohor bronze layer and no failure occurred due to separation of the samples from the interface. By performing tensile tests, it was found that the ultimate tensile strength increased from 430 to 488 MPa with increasing stand-off distance and explosive load. Polarization acquisition and impedance spectroscopy (EIS) tests showed that with increasing impact energy, the corrosion potential decreased and the corrosion current density increased significantly from 5.5 to 13.2 μA/cm².

The joining of dissimilar aluminum sheets is an important issue in the optimization of industrial joints due to the differences in physical, mechanical and metallurgical properties. In this study, the mechanical behavior and microstructural changes of bimetallic joints made of AA5052 and AA3105 alloys joined by two methods of TIG welding (TIG) and friction stir welding (FSW) were investigated and compared. First, preliminary experiments were carried out to optimize the parameters of the friction stir welding and TIG welding processes and to select appropriate levels of the process parameters. The results of mechanical experiments showed that in the FSW welded samples, the failure occurred mainly in the weld zone, but in the TIG welded samples, the failure occurred in the base metal. The tensile test results showed that the AA5052 sample had the highest tensile strength (273 MPa) and the highest elongation percentage (20%), and the F 3-5 welded sample with a strength of 89 MPa and 6% elongation performed worse than the T 3-5 welded sample and fractured in the weld area. The microhardness test results showed that the TIG welded sample had a higher hardness in the weld area than the FSW method due to the use of 5356 ER filler. Finally, by analyzing and comparing the results obtained from the tests related to the mechanical properties obtained from each method, it was found that the TIG method performed better than FSW in joining some alloys.

This study presents a comparative evaluation of SMAW and GMAW welding processes for blade-to-shaft joints in St37 steel industrial mixers operating in lead-processing environments. The effects of welding process selection and joint geometry modification on the microstructural and mechanical properties of the welded joints were investigated. The results showed that the use of the GMAW process reduced the average heat-affected zone (HAZ) width from 1532 μm to 871 μm, corresponding to a 43.1% reduction compared to SMAW. In addition, the ultimate tensile strength increased from 376 MPa for SMAW joints to 400 MPa for GMAW joints, representing a 6.4% improvement. Microhardness measurements revealed an increase in the average HAZ hardness from 145 HV to 160 HV, corresponding to a 10.3% increase. Microstructural examinations also revealed noticeable differences in the characteristics of the weld metal and HAZ produced by the two welding processes. The findings indicate that the combination of GMAW and optimized joint geometry can improve the mechanical performance and reliability of blade-to-shaft joints in industrial mixers.