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.

Severe plastic deformation is considered one of the methods of producing materials with sub-micrometer and even ultra-fine-grained materials. The constrained groove pressing process is one of the severe plastic deformation methods for sheet-formed materials. In this research, the wear resistance and hardness of 304L Stainless Steel after being subjected to constrained groove pressing were analyzed with respect to the pass number. It was found that the hardness of the initial annealed sample was 163.5 HV, and It was equal to 373.7 and 389.5 HV in the first and third passes, showing an increase of 128% and 138% of hardness in the first and third passes compared to the initial sample. Moreover, the sample wear rate at the normal load of 30 N and 50 N was 0.049% and 1.16% for the initial annealed state, 0.041% and 0.56% for the first pass condition, and 0.036% and 0.24% for the final pass situation. The main reasons for the hardness improvement and wear resistance increase are related to the application of cold work and the increase of dislocation density. It should be mentioned that the dislocation movement makes the material more ductile (increase in the plastic deformation) if the density of dislocations in the material exceeds a certain limit, it leads to the interaction of dislocations and their locking; so, the material becomes more brittle. It can be concluded that the improvement of hardness and wear resistance increases with the addition of the pass number.

In this study, the mechanical properties of dissimilar welding of Super duplex Stainless Steel UNS 32750 to austenitic Stainless Steel AISI 304L by gas tungsten arc welding process with direct current electrode negative polarity was investigated. For this purpose, two filler metals including ER25104L and ER309LMo were used. In order to achieve suitable structure and excellent mechanical properties in the mentioned joints, controlling of the heat input and pre heating were among the effective and controllable parameters. Microstructures of the weld metals, were evaluated using optical microscopy and scanning electron microscopy was used to analyze fracture surface. In addition, the mechanical properties including the bend test, ultimate strength, impact resistance and hardness were investigated. All the specimen underwent ductile fracture in HAZ in the tension test. The maximum fracture energy related to the ER 25104L the welded specimen. The maximum and minimum hardness corresponded to the ER 25104L and ER 309LMo, respectively. Finally, it was seen that for the joints, between the super duplex Stainless Steel UNS 32750 to austenitic Stainless Steel AISI 304L, the ER 251 04L filler provided the optimum qualities.

Effect of continuous heating after cold deformation on the microstructural evolutions and corrosion behavior of SUS 304L metastable austenitic Stainless Steel was investigated. After cold rolling with the reduction in thickness of 80%, a microstructure consisting of elongated grains was obtained, in which the X-ray diffraction (XRD) analysis revealed the formation of 96 vol.% strain-induced martensite. The subsequent continuous heating up to 750 °C led to full reversion/recrystallization and the development of an ultrafine grained (UFG) microstructure with an average grain size of 0.45 µm. Continuous heating up to higher temperatures resulted in a significant grain growth, where the average grain size of samples that heated up to 850, 900, 950, and 1100 °C were obtained as 2.5 µm, 5.5 µm, 14 µm, and 45 µm, respectively. The Hall-Patch relationship of H = 155 + 106/√D was developed for the dependence of hardness on the average grain size (D). By grain refinement, corrosion current density (iCorr) increased leading to the worsening of uniform corrosion resistance. However, breakdown potential (EBr) increased by grain refinement, indicating the improved pitting resistance. The Hall-patch-type equations of iCorr = 0.0147 + 0.4458/√D and EBr = 0.1964 + 0.0695/√D were proposed for correlating the corrosion parameters to D.

In this investigation, the effect of grain size on the corrosion behavior of 304L Stainless Steel has been studied.Samples with grain sizes of 0.5, 3 and 12 micrometers were fabricated through formation of strain-induced martensite by 80% cold rolling of the Stainless Steel sheets at -15oC and its reversion to austenite during annealing at 900oC for 1, 5 and 180 min. The corrosion behavior of samples with different grain sizes was investigated by cyclic polarization experiments andimmersion tests in 0.1 M hydrochloric acid (HCl). The polarisation tests showed no differences in uniform corrosion rates of the samples. The results of the cyclic polarisation and immersion tests showed that decreasing the grain size improved the pitting corrosion resistance from 290 mVAg/Agcl for grain size of 12 micrometers to 420 mVAg/Agcl for grain size of 0.5 micrometers.

In this study, the microstructure and mechanical properties of dissimilar welding of Super duplex Stainless Steel UNS 32750 to austenitic Stainless Steel AISI 304L by gas tungsten arc welding process with direct current electrode negative polarity was investigated. For this purpose, two filler metals including ER25104L and ER309LMo were used. The microstructure of the different zone in each joint, including weld metals, heat affected zone, interface were evaluated using optical microscopy and the relationship between mechanical properties and microstructure of welded joints is evaluated. Results indicate that austenitic and ferritic structures such as dendrite in the weld metal 25104L, 309LMo weld metal was observed as the primary ferrite with austenitic matrix. In addition microstructure was seen as skeleton ferrite morphology. In addition, the mechanical properties including the bend test, ultimate strength, impact resistance and hardness were investigated. All the specimen underwent ductile fracture in HAZ in the tension test. The maximum fracture energy related to ER25104L. The welded specimen with ER25104L filler metal showed the maximum elongation. The maximum and minimum hardness corresponded to the ER25104L and ER309LMo, respectively. Mechanical properties of joints welded by the two kinds of filler metals are satisfactory, althought the mechanical properties of 25104L filler metal is superior to that by 309LMo filler metal. Based on the present work, it is concluded that 25104L provides the optimum qualities for joining dissimilar metals between 32750 super duplex Stainless Steel and 304L austenitic Stainless Steel.

This research includes the preparation of a poly-eugenol layer on the surface of a Stainless Steel electrode by electropolymerization process, where the polymer was diagnosed using infrared spectroscopy and atomic force microscopy. The corrosion measurements of Stainless Steel 304L electrode were carried out before and after coating with polyeugenol in 3.5% of NaCl solution at four different temperatures in the range 298-328 K. Likewise, this study included the addition of nanomaterials such as ZnO and TiO2 to increase the efficiency of the polymeric layer formed against corrosion. The biological activity of the polymeric film was tested against bacterial Gram- positive Staphlococcus aureus (Staph.aure) and Gram-negative Escherichia coli (E.coli). Furthermore, the coating was treated with nanoparticles (ZnO and TiO2).

Gas tungsten arc welding is a popular process in those applications requiring a high degree of quality and accuracy. However, this process has a big disadvantage against the substantially high productivity welding procedures. Hence, many efforts have been made to improve its productivity. One of these efforts is the use of activating flux (A-TIG welding). In this study, the performance of A-TIG welding on 304L austenitic Stainless Steel plates has been presented. Two oxide fluxes, TiO2 and SiO2 were used to investigate the effect of A-TIG welding process on weld morphology, microstructure and mechanical properties of weldments. The experimental results indicated that A-TIG welding could increase the weld penetration and depth-to-wide ratio. It was also found that A-TIG welding could increase the delta-ferrite content of weld metals and improve the mechanical properties. Moreover, a 2D axial symmetric model was developed to simulate the flow behavior in the melting pool. These results were compared to those experiments carried out on a Stainless Steel (304L) melted by a stationary heat source.

In this study, commercially pure titanium/304L Stainless Steel explosion bonded clads have been annealed under argon atmosphere over the temperature range of 700-900°C for 1h.Microstructure of the clads have been investigated before and after anealing. X-ray diffraction studies revealed that the annealing products in the form of intermetallic phases were gradually formed at the interface of the annealed clads. It was also found that, the bonding zone width increased with temperature according to an Arrhenius type equation. On the base of this equation, the activation energy of bonding zone growth was found equal to about 66.5 kJ/mol. The bond strength of the diffusion annealed clads were evaluated stress relieved. The maximum average tensile strength of ~350MPa was obtained for the as-welded clad. It was found that the bond strength decreased with annealing at 700°C due to an increase in the width of brittle intermetallic layer.

The inhibition effect of three acetanilide compounds namely acetanilide (Ac1), o-methyl acetanilide (Ac2) and p-nitroacetanilide (Ac3) on the corrosion of 304L in 1 M HCl solution was studied by potentiodynamic polarization and electrochemical impedance spectroscopy methods. The results show that compound Ac3 is the best inhibitor and the inhibition efficiency follows the order: Ac3>Ac2>Ac1. Potentiodynamic polarization curves indicated that the inhibitors acted as mixed-type inhibitors. The adsorption of inhibitors on the Stainless Steel surface obeys to the Langmuir adsorption isotherm and has physisorption mechanism. All techniques employed in this study show the same order of inhibition efficiency.