Papers by Keyword: 316L

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Authors: Yun Zhou, Xiao Qing Zuo, Ting Zhang
Abstract: Pure 316L powder is used to mix with an additive to prepare a powder mixed paste. 316L honeycombs were fabricated by extruding the powder mixed paste, then dried and sintered. The volume shrinkage and the apparent density of extruded honeycombs after drying and sintering were measured. The effect of sintering temperature on the volume shrinkage, the apparent density and the structure of honeycombs had been studied. The results show that the volume shrinkage and the apparent density of sintered honeycombs increase with sintering temperature from 1120°C to 1200°C , the volume shrinkage varying from 42% to 57%, and the apparent density from 1.9 to 2.9g/cm3 for 80% solids fraction. The volume shrinkage decreases and the apparent density increases with solid fractions increasing. The structure of sintered honeycombs consists of matrix phase α-Fe(Cr,Ni) , complex compounds of silicon, oxygen and inclusion elements. There is oxide film forming on surface of sintered honeycombs.
Authors: M. Dourandish, Dirk Godlinski, Abdolreza Simchi
Abstract: The fabrication of complex-shaped parts out of Co-Cr-Mo alloy and 316L stainless steel by three-dimensional printing (3DP) is studied using two grades of each alloy with average particle size of 20 and 75 )m, respectively. To produce sound specimens, the proper 3DP processing parameters were determined. The sintering behavior of the powders is characterized by dilatometric analysis and by batch sintering in argon atmosphere at 1280°C for 2h. The 3DP process has successfully produced complex-shaped biomedical parts with total porosity of 12-25% and homogenous pore structure, which is suitable for tissue growth into the pores.
Authors: Prashant Poojary, L.K. Singhal
Abstract: Currently austenitic stainless steels, cobalt-chromium alloys and titanium alloys are used in body implants. As per ISO 5832-1, Cr-Ni-Mo alloy 316L with minimum 13% nickel is widely used for body implants. ASTM standard F 2229-07 also permits nitrogen strengthened essentially Ni-free Cr-Mn-Mo alloy (UNS S 29108) for this purpose. Nitrogen as austenite stabilizer is able to substitute nickel. It serves the dual purpose of increasing the strength as well as pitting corrosion resistance. This paper compares the corrosion behaviour of these two grades. Cyclic potentiodynamic tests were carried as per ASTM F2129 in Simulated Body Fluids (SBFs) like Ringers, Hanks and Phosphaste Buffer Saline solution at 37 °C, which corresponds to the human body temperature. The pitting potential was significantly higher for Ni free grade S29108 as compared to 316L. In addition, re-passivation potential of the S 29108 was also far superior than 316L. The reverse scan indicated that the breakdown of the passive film was not reached in S 29108, whereas a hysteresis loop was observed in 316L. The strength of annealed S 29108 is far superior and meets the property requirement of ISO 5832-1 for 316L under cold rolled conditions. Thus this alloy could replace annealed as well as cold rolled 316L as per ISO 5832-1. This promising alloy has an added advantage of being significantly cheaper as compared to 316L and other Ti, Co based alloys to enable cost effective medical care to common man. Keywords: High nitrogen stainless steel, 316L, Bio-Implants, Potentio-dynamic tests.
Authors: Marek Pagáč, Jiří Hajnyš, Jana Petrů, Tomáš Zlámal
Abstract: The paper deals with the comparison of surface hardness and porosity of stainless steel 316L (1.4404) produced by additive technology (SLM) and cold rolled steel. The subject of the paper is a comparison of two sets of samples where the first set of samples was made on a Renishaw AM400 with a laser output of 200 W and 400 W. In each set of samples, were the samples without heat-treated and heat-treated by annealing. Measurement of porosity and surface hardness were performed on all samples. The surface hardness of the material was evaluated by a static test according to Brinell CSN EN 10003-1. The porosity measurement was performed by the optical method. The measured values were compared with the reference material, which was cold-rolled steel, in which both the porosity and the hardness of the surface were measured.
Authors: A. Ismail
Abstract: Austenitic stainless steels especially 316L has been used extensively in many sectors including construction, medical and household appliances due to their highly resistance to corrosion attack, reasonable cost and excel in mechanical properties. However, in corrosive media, 316L are susceptible to localised corrosion attack especially in seawater and high temperature. The corrosiveness of media increased as the anions contents increased. This paper presents the corrosion mechanism of 316L exposed to high concentration of sulphate in the salinity of seawater. The solution (media) was prepared according to the same composition as seawater including pH, salinity and dissolved oxygen. The corrosion mechanism were characterized to breakdown potential (Eb) of 316L which are the potential once reaches a sufficiently positive value and also known as pitting potential. This is the most point where localized corrosion susceptibility to evaluate and considered a potential, which could be an appropriate point according to any given combination of material/ambient/testing methods. The Eb value were identified at 4°C, 20°C, 50°C and 80°C and compared with Eb value of 316L in seawater. The Eb value of 316L in high sulphate are higher compared to seawater in every temperature which elucidate that some anions accelerate corrosion attack whereas some anions such as sulphate behaves as inhibiting effect to 316L.
Authors: Jaroslav Polák, Martin Petrenec, Jiří Man
Abstract: Austenitic stainless steel was cycled at a series of temperatures in the interval from 296 K to 113 K. Constant plastic strain amplitude loading at different levels of plastic strain amplitude and testing similar to multiple step test method were applied at different temperatures. The stress amplitude was continually recorded and selected hysteresis loops were stored and later analyzed using statistical theory of the hysteresis loop. Effective stress component and probability density function as a function of temperature were evaluated. The results were discussed in terms of the temperature dependence of the cyclic yield stress and its sources.
Authors: A. Ismail, Lidiyawati Suhairi
Abstract: Cyclic polarization test was used to determine the breakdown potential of passive film for stainless steel 316L at different temperatures (20°C, 30°C, 40°C, 50 °C) and different salinity (15%, 25%, and 35%). The results show the highest breakdown potential occur at low temperature and low salinity indicate that incresing the temperature and salt content in seawater will increasing the corrosion attack on 316L. Increasing the temperature from 20°C to 50°C was decrease the Eb value for 75%. Before and after testing, visible pits and hardness for each sample were observed by using Scanning Electron Microscopy (SEM) and Vickers hardness testing. It was found that at temperature 20°C, it can be seen that number of pits is more but the pits size is a bit tiny. However, the number of pits reduce as the temperature and salinity increased but the size of the pit become larger and wide which indicate that pitting has propagate during that period. Furthermore, increasing the temperature from 20°C to 50°C also lead to increased the hardness different value which indicate that reducing in hardness properties of 316L at increasing salinity because of corrosion attack.
Authors: A. Karimian, Hassan Farhangi, A. Amari Allahyari
Abstract: In this research, variations of tensile properties and fracture behavior of 316L austenitic stainless steel weld metal as a function of aging temperature and time have been investigated. Stainless steel plates were butt-welded using GTAW process. Weld metal tensile specimens were subjected to various aging heat treatments at temperatures of 750 and 850°C for periods of 1 to 100 hours prior to tensile tests at 25 and 500°C. Dissolution of delta-ferrite and formation of sigma phase network during aging resulted in a mild increase in tensile strength and significant reduction in ductility, particularly at 25°C. Although fracture surfaces exhibited ductile features, the dimple morphology and the macroscopic fracture mode were found to be affected by aging. The unaged weld metal exhibited a classic mode of cup and cone fracture, whereas slant and flat types of fracture modes were observed in the aged weld metals, with the slant mode being dominant at 500°C. The slant mode was associated with deformation localization along arrays of primary voids, nucleated at cracked sigma phase particles, oriented at about 45° to loading direction. The transition in the fracture mode is further discussed based on variations in the dimple morphologies and strain hardening exponent.
Authors: C.L. Santos, G. Vasconcelos, H.S. Oliveira, L.G. Oliveira, J.F. Azevedo, R. Riva
Abstract: This study shows the influence of the temperature in the Direct Forming Laser process (DFL) of 316L stainless steel metal powder. Results shows that an increasing in the sample surface temperature can improve the laser beam absorption in the DFL process. A pre-heating in the substrate and in the powder contributed to decrease the time to reach the melting point and to improve the surface roughness. This effect was investigated with constant lasers parameters (scanning speed and intensity) and a heating in the samples in the temperature range of 20o to 200o C. It was possible to evaluate the DFL process and to optimize the quality of the sample surface roughness. These results will benefit the knowledge of the DFL technology that can be applied in the development of turbine blades.
Authors: Mara Cristina Lopes de Oliveira, Isolda Costa, Renato Altobelli Antunes
Abstract: Bipolar plates play main functions in PEM fuel cells, accounting for the most part of the weight and cost of these devices. Powder metallurgy may be an interesting manufacturing process of these components owing to the production of large scale, complex near-net shape parts. However, corrosion processes are a major concern due to the increase of the passive film thickness on the metal surface, lowering the power output of the fuel cell. In this work, the corrosion resistance of PIM AISI 316L stainless steel specimens was evaluated in 1M H2SO4 + 2 ppm HF solution at room temperature during 30 days of immersion. The electrochemical measurements comprised potentiodynamic polarization and electrochemical impedance spectroscopy. The surface morphology of the specimens was observed before and after the corrosion tests through SEM images. The material presented low corrosion current density suggesting that it is suitable to operate in the PEM fuel cell environment.
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