M. Ahl Sarmadi, M. Shamanian, H. Edris, A. Behjat, M.a. Mohtadi Bonab, J. Szpunar,
Volume 1, Issue 1 (1-2016)
Abstract
In this study the microstructure and mechanical properties of super duplex stainless steel UNS S32750 welding was studied. For this purpose, the method of gas tungsten arc and filler metal AWS ER2594 with a diameter of 4.2 mm was used. In order to investigate the microstructure light microscopy and electron microscopy equipped with backscatter electron diffraction were used. Mechanical properties were studied by hardness and tensile tests. Weld metal had Cast structure with austenite in the dendrite form located in ferrite matrix. It was also observed in the melting zone after welding, the ferrite volume fraction decreased to 50 percent 60% base metal ferrite) ,Due to the low cooling rates and high heat input method in the gas tungsten arc welding. Vickers micro-hardness test method was carried out on the samples showed that average about 285 Vickers hardness of base metal; however, hardness in the fusion region due to increased austenite fraction fell to 250 Vickers. But hardness in the heat-affected zone due to lower volume fraction of austenite and ferrite phase formation of chromium carbide intermetalic compounds increased to 340 Vickers. The results of the tensile test showed that the tensile strength decreased with increasing heat input, because of increase the size of grains due to the increased heat input.
Morteza Abbasi, Hamidreza Najafi, Alireza Khodabandeh,
Volume 4, Issue 1 (8-2018)
Abstract
Dissimilar welding of AISI 304L austenitic stainless steel to AISI 409 ferritic stainless steel with GMAW process usingtwo Ar-O2 and Ar-CO2 shielding gas mixtures was studied. ER316LSi and ER309LMo filler metals were chosen by considering 5 and 15% delta ferrite according to the Schaeffler equations and diagram. Based on the observations, both filler metals accompanied by Ar-2%O2 shielding gas resulted in acceptable weldments. Yield strength and UTS of tensile samples were 288 and 424 MPa, respectively. All tensile samples fractured in the ferritic base metal. Microhardness test results demonstrated that the maximum hardness of 190-200 HV was obtained from ER316LSi weld metal. The minimum hardness of 145 HV was found in the HAZ of 409 side mainly due to the grain coarsening. Microstructural examinations revealed needle-like precipitates formed perpendicular to each other in the HAZ of 409 stainless steel. It seemed that the pre-existing TiC precipitates evolved into the needle shape precipitates as a result of rapid heating and cooling rates during the welding process.
