جستجوی مقالات مرتبط با کلیدواژه « 316L stainless steel » در نشریات گروه « مواد و متالورژی »

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.

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.

In this study, the addition of organic methionine inhibitor (as an eco-friendly inhibitor) to 0.1 M sulfuric acid media on corrosion resistance of 316L austenitic stainless steel (fabricated by rolling method and three-dimensional (3D) printing method) was investigated. Open-circuit potential electrochemical test and impedance, and structural tests such as optical and electron microscopy and x-ray photoelectron spectroscopy were conducted. The results showed that the corrosion resistance in the presence of inhibitor was higher than the sample without inhibitor and the inhibitory efficiency of methionine was increased up to 64% and the resistance to surface transfer between metal oxide and electrolyte was improved up to 2.77 times. The addition of methionine reduced the surface roughness and accumulation of the surface cavities. The chemical and physical adsorption mechanism of the inhibitor (negatively charged side adsorption of the methionine molecule with positively charged anodic regions of the metal surface) occurred at all points on the surface of the sample with the inhibitor. Also, the amount of oxygen in the cavities was reduced and the distribution of sulfur was uniform. The thickness of the passivator oxide layers was calculated more than the sample without inhibition due to the addition of inhibitor.

Both Ti-6Al-4V and 316L stainless steels are widely used as engineering alloys in many modern industries, especially aerospace, gas turbine engines and heat exchangers due to high mechanical properties, high creep, fatigue, and corrosion resistance. Fusion welding of these alloys is not easily possible due to their incomplete solubility in each other. Brazing is one of the best choices for joining dissimilar alloys. Infrared brazing is a novel process characterized with a high heating rate up to 500 °C/min. Accordingly, it is expected that both erosion of the substrate and excessive growth of intermetallic phases in the brazed joint are significantly decreased. This study is focused on the infrared brazing of Ti-6Al-4V and 316L stainless steel to investigate the influence of brazing parameters (brazing alloy, temperature and time) on microstructure and mechanical properties of base metals with CBS 34 (Ag-based) braze filler foils. Brazing was performed in a home-made infrared furnace at temperatures of 750, 780, 800, 850 and 900 °C for 3-5 min. Qualities of the brazed joints were evaluated by microstructure and phase constitution of the bonded joints with light optical microscope (LOM) and scanning electron microscope (SEM). Mechanical properties of the brazed joints were evaluated by hardness test. The optimum brazing parameters were at 850 °C-5 min for CBS 34 filler foils.

Titania-halloysite nanotubes (HNTs) nanocomposite coatings were electrophoretically deposited on the 316L stainless steel substrate. Two-component suspensions of titania and HNTs particles (different ratios of titania : HNTs wt% and constant particles concentration of 10g/l) in ethanol with 0.5g/l of polyethyleneimine (PEI) as the dispersant were used for electrophoretic deposition (EPD) experiments. EPD was performed at 60V for 10 and 60s using a two-electrode cell. Coatings were sintered in vacuum furnace and at 700˚C for 1h. Microstructural, element mapping and EDX analysis were performed on the coatings using a SEM. It was found that HNTs reinforce the microstructure of coatings and prevent from the cracking of coatings deposited from the suspensions with HNTs>25wt%. The corrosion rate of substrate coated at 10 and 60s using the suspensions with different ratios of titania: HNTs was measured by electrochemical polarization technique in Ringer solution and at 37˚C. The corrosion rate of substrates coated for 60s decreased as the HNTs content increased in the suspension due to the crack-free microstructure of prepared coatings. However, the corrosion rate of substrates coated at 10s increased as the HNTs content increased in the suspensions due to the less packing density and thickness of prepared coatings.

In this study, the electrochemical behavior of passive films anodically formed on 316L stainless steel in 0.05 M sulfuric acid has been examined using electrochemical impedance spectroscopy (EIS). For this purpose, passive films were formed potentiostatically at selected potentials for 1 h and then EIS measurements were done. For EIS measurements, an excitation voltage of 10 mV and an applied frequency ranging from 100 kHz to 10 mHz have been used. Results showed that the interfacial impedance and the polarization resistance (Rpol) initially increase with applied potential, within the low potential passive. However, at a sufficiently high potential passive (E > 0.5 V), the interfacial impedance and the polarization resistance decrease with increasing potential. Also, an electrical equivalent circuit based on the point defect model (PDM) was suitable to the actual passivation process. In this electrical equivalent circuit, the total impedance was taken to be the sum of impedance of steel/passive film interface, passive film and passive film/solution interface.