Low-cost Stainless Steel Research Articles

Grain size refinement and effect on the tensile properties of a novel low-cost stainless steel

In this study, a novel 20LH5 austenitic stainless steel (AUSS) with various grain sizes was produced. The purpose of this paper is to analyse the effect of the grain size on the tensile fracture morphology and mechanical properties. After a phase reversion process (large ductility cold rolling and annealing), stainless steels with different microstructures comprising coarse grains (CGs) (~9.2 μm) to fine grains (FGs) (~2.1 μm) to ultrafine grains (UFGs) (~1.4 μm) were observed. Tensile tests were then carried out to verify the grain refinement strengthening mechanism. The results show that the mechanical properties in materials that possess UFGs reached a tensile strength of ~1090 MPa, a yield strength of ~530 MPa and an elongation rate of ~47%, which is much better than those of materials with FGs, CGs, and most 300 series AUSSs. Furthermore, the voids in UFG AUSSs were densely distributed and finer than those in the other two counterparts. This indicates that a decreased grain size contributed to a decreased dimple size; that is, the ductility and strength were increased.

Study of Transport Behavior in an Anion Exchange Membrane Fuel Cell

Currently, anion exchange membrane fuel cells (AEMFC) are gaining strong interests from researchers because it provides great potential for applying non-precious metal in comparison to the proton exchange membrane fuel cells (PEMFC). The alkaline oxygen reduction reaction (ORR) has lower cathodic activation overpotential than ORR in a PEMFC. In addition, low-cost stainless steel can be used as flowfield material, instead of more expensive metals or high-purity graphite because corrosion of the bipolar plate is less of an issue in the alkaline environment. However, there are still many technical challenges existed in AEMFC research. One key challenge is related to the transport of reactants and product in and out of the catalyst layer. Different from a PEMFC, water is actively participating in anodic hydrogen oxidation reaction (HOR) as a product and cathodic ORR as a reactant. Therefore, anode flooding and cathode drying are concerns for operating an AEMFC under high current density conditions. This complicates the study of transport behavior in an AEMFC because transport limitation may occur due to one or a combination of hydrogen, oxygen, hydroxide, and water. Additionally, hydroxide transport in the membrane strongly relies on proper hydration, which may induce severe polarization losses due to membrane and ionomer conductivity caused by drying. Therefore, adequate water balance combined with effective reactant/product transportation are essential in achieving good performance for an AEMFC. In this work, we focus on studying the effect of operating conditions on fuel cell performance experimentally. Key parameters include relative humidity, temperature, pressure, and inlet gas concentration. An in-situ diagnostic tool, limiting current method1, is employed to analyze transport behaviors in an AEMFC. Differential conditions are achieved by using a straight parallel flowfield with 2 cm2 active area as shown in Figure 1. Our aim is to identify sources of transport limitations and quantify their effect under various operating conditions. Detail experimental and analytical results will be shared at the conference.

Fabrication of multiple through-holes in non-conductive materials by Electrochemical Discharge Machining for RF MEMS Packaging

Formation of multiple through-holes arrays in a 400 μm thick silica substrate is reported for the first time by a cost-effective electrochemical discharge machining (ECDM). Customized multi-tip array tools having varying pitches and tip sizes were fabricated in low-cost stainless steel material. The average tool tip size, pitch, and tip length were 150 μm, 1.5 mm and 15 mm, respectively. Experiments were performed with varying voltages, duty cycles, and pulse frequencies to study their effects upon different geometrical characteristics such as through-hole entrance size, overcut and heat affected zone (HAZ). The effect of tool tip length on hydrogen gas bubble entrapment between the tool tips was investigated. Additionally, the effect of three different electrolytes i.e., NaOH, KOH, and H2SO4 were investigated. Significant improvements in the quality of the through-holes were obtained with KOH electrolyte over NaOH electrolyte. However, the material removal with acidic H2SO4 electrolyte was negligible as compared to NaOH and KOH. The least radial overcut (<50 μm) and HAZ width (61 μm) at the optimized parameters were observed in the KOH electrolyte. The depths of machined holes were in good agreement with the FEM based numerical simulation results. Compared to conventional methods like plasma etching and laser drilling, a large number of through-holes can be machined at customized locations in less than 10 min. Upon metal filling, these through-holes can be used as ‘through-glass-via’ (TGV) interconnects in 3D radio-frequency (RF) MEMS packaging applications.

Reduced turn-on field through solution processed MoS2 nanoflakes anchored MWCNTs

Abstract An investigation of field emission on solution processed MWCNTs, MoS2 and MoS2 anchored MWCNTs thin films on low cost stainless steel substrates have been performed. Decorative morphology of MoS2 nanoflakes over MWCNTs interconnected high surface area nanonetwork supports the active path for the application of field emission. Drastic diminishing in turn-on field value has been obtained for MWCNTs/MoS2 nanocomposite compared to bare MWCNTs and MoS2. Hence, present investigation opens path for the development of low-temperature solution processed MWCNTs/MoS2 thin film in the field of nanoelectronics and the used process can be integrated for large scale.

Nutrient recovery and energy production from digestate using microbial electrochemical technologies (METs)

This work aimed to test both energy production and the recovering of phosphorus from high solid content digestate by coupling microbial electrochemical technologies (MET) with a crystallization process. Digestate coming from an anaerobic digester was used as the feeding substrate for a Microbial Fuel Cell (MFC) and a Microbial Electrolysis cell (MEC) to produce electricity and H2, promoting P removal (as struvite: MgNH4PO4∙6H2O) as consequence of the pH increase at the cathode level. MECs were equipped with low cost stainless steel mesh cathodes to be compared with a benchmark cathode, i.e. Pt electrode, and used to reduce the METs cost. The effluents coming from METs were then treated to further reduce P content by promoting struvite precipitation in a crystallization device, by adding either pure Mg salt (MgCl2) or an Mg by-product (seawater bitterns). MFC tests showed a Coulombic efficiency of 35%, with a volumetric power produced of 14.2 ± 0.15 W m−3. MEC (+1.07 V vs SHE) systems produced 1.90 ± 0.04 LH2 L−1d −1 using a stainless steel mesh (SSM) and 2.02 ± 0.03 LH2 L−1d −1 using a platinum cathode. Both MET treatments led to a phosphate (PO43−) reduction of between 21% and 30% and an organic load reduction (chemical oxygen demand) of between 27% and 44% of the digestate. The addition of MgCl2∗6H2O or seawater bitterns, in the molar ratio of 1.6: 1 (Mg:P) led to a further reduction of phosphate (PO43−) of between 60% and 70% with an overall reduction of phosphate (PO43−) of ≈90%. These results show how the MET systems could be used for COD and nutrients reduction as well as H2 or electricity production from digestate. Moreover, the SSM cathode gave a similar performance to the Pt cathode, while seawater bitterns seem to be useful in substituting MgCl2∗6H2O. The results obtained showed that the combination of the system proposed in this work with a biogas plant could be a low cost solution for the recovery of nutrients and for hydrogen or electricity generation from digestate.

Efficient electrochemical recovery of dilute selenium by cyclone electrowinning

Efficient recovery of selenium from the dilute acidic solution is of great importance to the cleaner production of this scattered element. In order to overcome the bottlenecks of low recovery ratio and severe environment issues in conventional processes, an easy-operation electrochemical recovery process of Se was developed using low-cost stainless steel cathodes. It has been demonstrated that Se ions can be successfully electrodeposited, but the recovery ratio of Se is significantly limited by the low Se concentration. Consequently, a cylinder turbulent electrochemical reactor was employed for the extraction of metals from dilute solution (0.3 g/L Se(IV)). 97.6% selenium was successfully recovered within 90 min, nano-sized and mesoporous selenium product was also obtained due to the excellent mass transport effect. This mass transport-enhanced technique may serve as a promising alternative for metal and metalloid electrowinning.

Efficient electrochemical recovery of fine tellurium powder from hydrochloric acid media via mass transfer enhancement

Abstract Recovery of tellurium from industrial waste streams is of significant importance for the supply of this scattered element. In order to overcome the bottlenecks of high reagents consumption and low recovery efficiency in conventional processes, a novel electrochemical recovery of Te from hydrochloric acid solution was first developed using low-cost stainless steel plate. Due to the high mobility of Te in HCl systems, there is a good electrodeposition behavior of Te(IV) from both the thermodynamic and kinetic considerations. It has been identified that Te electrodeposition is diffusion controlled quasi-reversible reaction, in which the mass transfer can significantly determine the recovery performance and deposit quality. Therefore, a cylinder turbulent reactor with larger surface area cathode was employed for the extraction of tellurium from dilute solution. Microscale Te powder was successfully obtained with a recovery ratio of 96.1% and a current efficiency of 84.3%, while the side reactions of chlorine evolution and TeO2 formation were efficiently inhibited. This mass transfer-enhanced electrodeposition may serve as a promising alternative to overcome the drawbacks of existing valuable element recovery and water purification.

Psychrophilic methanogenesis of food waste in a bio-electrochemical anaerobic digester with rotating impeller electrode

Psychrophilic bio-electrochemical anaerobic digestion (PBEAD) is a promising new technology for improving methane production at low temperatures via supply of low energy. In this study, a PBEAD reactor operating at 19.8 ± 2.9 °C equipped with a low-cost stainless steel (SUS304) rotating impeller electrode was manufactured to observe the efficiency of methane production and changes in archaeal communities at a high organic loading rate (OLR). Stable methane production was achieved without VFA accumulation and pH decrease in the PBEAD reactor up to an OLR of 4.5 kg/m3·d owing to H2-dependent methylotrophic and hydrogenotrophic methanogens, which converted H2 into methane. In the case of an OLR of 6.0 kg/m3·d, methane production decreased significantly due to decreased pH and accumulated VFAs, but recovered on increasing the alkalinity. The maximum energy efficiency of 71.7% confirmed the high performance of the PBEAD reactor equipped with an SUS304 rotating impeller electrode.

Conductive Hydrogel Electrodes for Delivery of Long-Term High Frequency Pulses

Nerve block waveforms require the passage of large amounts of electrical energy at the neural interface for extended periods of time. It is desirable that such waveforms be applied chronically, consistent with the treatment of protracted immune conditions, however current metal electrode technologies are limited in their capacity to safely deliver ongoing stable blocking waveforms. Conductive hydrogel (CH) electrode coatings have been shown to improve the performance of conventional bionic devices, which use considerably lower amounts of energy than conventional metal electrodes to replace or augment sensory neuron function. In this study the application of CH materials was explored, using both a commercially available platinum iridium (PtIr) cuff electrode array and a novel low-cost stainless steel (SS) electrode array. The CH was able to significantly increase the electrochemical performance of both array types. The SS electrode coated with the CH was shown to be stable under continuous delivery of 2 mA square pulse waveforms at 40,000 Hz for 42 days. CH coatings have been shown as a beneficial electrode material compatible with long-term delivery of high current, high energy waveforms.

Study of Impact Erosion of Oil and Gas Flowlines with Micro-sized Sand Particles

The oil and gas produced from the reservoirs of relatively low formation strength inevitably carry micro-sized sand particles, which adversely influence the flow-lines and other installations. The financial deliberations favor the choice of low-cost metals, in general, carbon steel as a flow-line material. Yet, there are many cases where carbon steel been substituted with a low-cost stainless steel. The corrosion resistance of the stainless-steel is well accepted. However, there is another type of deformation that is not well studied and understood is its erosion resistance. The objective of this study is to investigate the factors affecting the erosion of stainless steel placed in a dry sand stream of micro-size particles. The manipulated variables were sand size, impingement angle, gas flow velocity, and nozzle distance. The obtained results showed that the large particle size, high fluid-flow velocity and short nozzle distance would result in more severe erosion of the stainless-steel coupons.

Fatigue Properties of Ultra-Fine Grain Austenitic Stainless Steel and the Effect of Hydrogen

The fatigue properties of ultra-fine grain austenitic steel (UFG16-10), which has a 1 μm average grain size, were studied as part of the project aimed at the development of high-strength low-cost stainless steels for hydrogen service. The fatigue properties of the UFG16-10 were compared with that of a coarse grain material with the same chemical composition (CG16-10) and two kinds of commercial steels, JIS SUS316 and JIS SUH660. The fatigue strength of the UFG16-10 was 2.8 times higher than that of the CG16-10. The effect of hydrogen on the fatigue limit of the UFG16-10 was not significant. However, the fatigue life of the UFG16-10 was reduced by hydrogen in the short life regime. In the fatigue crack growth test, the UFG16-10 showed a good crack growth resistance that was equivalent to that of the SUH660 and significantly higher than that of the SUS316. However, the crack growth rate was significantly accelerated by hydrogen. The cause of the hydrogen-assisted fatigue crack growth of the UFG16-10 was transformation of the microstructure at the crack tip from austenite to strain-induced martensite. This was also the cause of the reduced fatigue life of the hydrogen-charged UFG16-10.

Additives-assisted electrodeposition of fine spherical copper powder from sulfuric acid solution

Metal removal and recovery from wastewater is of great importance for the environmental protection and resources sustainability. In this study, the synergistic effect of additives towards the electrochemical recovery of Cu was illustrated using low-cost stainless steel cathode. It has been identified that potassium ferrocyanide has the effect of grain refining, and 2, 2′-dipyridine has the effect of spherical growth. Therefore, fine spherical copper deposited product is firstly obtained in the presence of two target-specific additives from dilute solution, and satisfied current efficiency is achieved. This additives-assisted electrodeposition approach may serve as a promising alternative to overcome the bottlenecks of existing metal recovery and water purification.

Electro-Catalytic Biodiesel Production from Canola Oil in Methanolic and Ethanolic Solutions with Low-Cost Stainless Steel and Hybrid Ion-Exchange Resin Grafted Electrodes

Biodiesel is a growing alternative to petroleum fuels and is produced by the catalysed transesterification of fats in presence of an alcohol base. Transesterification processes using homogeneous catalysts are considered to be amongst the most efficient methods but rely on the feedstock quality and low water content in order to avoid undesirable saponification reactions. In this work, the electro-catalytic conversion of canola oil to biodiesel in a 1% aqueous methanolic and ethanolic reaction mixture was performed without the addition of external catalyst or co-solvent. An inexpensive stainless steel electrode and a hybrid stainless steel electrode coated with an ion-exchange resin catalyst were used as cathode materials while the anode was composed of a plain carbon paper. The cell voltages were varied from 10 to 40 V and the reaction temperature maintained at 20 or 40°C. The canola oil conversion rates were found to be superior at 40°C without saponification reactions for cell voltages below 30 V. The conversion rates were as high as 87% for the hybrid electrode and 81% for the plain stainless steel electrode. This work could inspire new process development for the conversion of high water content feedstock for the production of second-generation biodiesel.

Electrodeposited Inconel and Stellite like Coatings for Improved Corrosion Resistance in Biocombustors

Various electroplated coatings from [Ni/Co]-Cr-[Mo/Fe] systems, were tested to assess their potential to enhance lifetime performance of low-cost stainless steels exposed to bio-combustor operating conditions. A wide range of electrodeposition processing conditions and electrolytes were evaluated based upon an ability to: (1) design REACH compliant electrolytes that enable a wide range of potentially corrosion resistant alloys to be electrodeposited; (2) scale the process to enable compositionally and structurally uniform coatings to be formed onto SS test pieces; and (3) maintain coating adherence and corrosion resistance during accelerated high temperature corrosion studies. Within this program we developed uniform, dense, well-adhered alloy coatings of various compositions, and performed accelerated high temperature corrosion studies to ascertain which alloys maintained better substrate adherence and corrosion resistance when exposed to salted thermal exposure conditions of 700ºC for 500 h.

Electrodeposited Inconel and Stellite like Coatings for Improved Corrosion Resistance in Biocombustors

Biomass is ubiquitous within the Nation and embodies tremendous potential as a renewable energy resource. Virtually all Citizens have access to at least modest quantities of biomass—many counties in the Nation have access to over 100,000 tonnes of local solid biomass resources[1]. One challenge of biomass as a combustion fuel is that, depending on the source, its chemical composition, moisture content, etc. (and thus its combustion behavior) can vary considerably[2]. This is in contrast to fossil fuels such as gasoline, kerosene, diesel, and natural gas which generally have been processed into highly refined hydrocarbon mixtures. Many of these impurities in biomass pose significant corrosive challenges to the types of apparatus (Figure 1) commonly used to carry out the combustion operations, which for cost reasons are often constructed of mild or low-alloy steels. Relevant corrosive species include alkali halides (borne, e.g., by fly ash particulates), mineral/halogen acids and water; as well as various others such as sulfur and nitrogen oxides. While upgrading the combustor components to alloys such as stainless steels or superalloys of nickel, cobalt, etc. would substantially eliminate many corrosion problems; such a change in materials of construction would in general be cost-prohibitive. There is a need to develop corrosion-resistant alloy coatings onto stainless steel base materials with the goal of increasing the functional lifetime of biomass combustion apparatus, while reducing the component cost. Within this context, the objective of the present work was to develop a cost effective, scalable, and flexible electrodeposition based coating process that can be used to apply cost effective corrosion resistant coatings to low cost stainless steel substrates for enhanced corrosion resistance in sensitive regions of existing and next generation bio-combustors. The manufacturing process involves using electrodeposition for application of binary and/or ternary alloys consisting of [Ni/Co]-Cr-[Mo/Fe] onto a low cost substrate surface, and subsequently accelerated high temperature corrosion evaluation. Therefore, in this study various electroplated coatings, from [Ni/Co]-Cr-[Mo/Fe] systems, were tested to assess their potential to enhance lifetime performance of low-cost stainless steels exposed to bio-combustor operating conditions. A wide range of electrodeposition processing conditions and electrolytes were explored in order to understand these effects on the deposit composition, structure and high-temperature corrosion resistance properties. Among those evaluated, NiCr coatings with Ni and Cr contents of approximately 60 and 40 wt% exhibited superior corrosion resistance when exposed to an aggressive high temperature corrosive treatment (~700°C, 500 hr, coating surface salted with ~3 mg/cm2 every 100 hours). Under this environment, NiCr coating on 304 SS exhibited a 70% lower weight loss than 304 substrate exposed to an identical treatment. This leads to a potential lifetime improvement of up to 3.4 times that of its base material while producing a lower cost alternative to using bulk corrosion resistance materials. Acknowledgements: The financial support of DOE Contract No. DE-SC0013870 is acknowledged. REFERENCES [1] “Solid Biomass Resources by County.” National Renewable Energy Laboratory, United States Department of Energy. Online resource: http://www.nrel.gov/gis/images/biomass_2014/national_ biomass_solid_total_2014-01.jpg. Accessed 9 Jan 2015. [2] Jenkins, B.M., Baxter, L.L., Miles, T.R., Jr., Miles. T.R. “Combustion properties of biomass.” Fuel Processing Technology 54: 17-46 (1998). Figure 1

Mass transport-enhanced electrodeposition for the efficient recovery of copper and selenium from sulfuric acid solution

Abstract Recovery of selenium from copper-based sulfuric acid solution is of significant importance for the supply of this scattered metal. In order to overcome the drawbacks of high energy/reagents consumption and low recovery ratio in conventional processes, a cost-effective electrochemical recovery process of Se and Cu was first developed using low-cost stainless steel cathodes. It has been demonstrated that Se and Cu ions can be simultaneously electrodeposited, and the co-deposition is mass transport controlled quasi-reversible reaction. Consequently, a cylinder turbulent cell with larger surface area cathode was employed for the extraction of metals from dilute solution (2.0 g/L Cu 2+ and 0.3 g/L Se 4+ ). Nanosized powder was obtained due to the excellent mass transport. 93.2% copper and 97.6% selenium was successfully extracted with a current efficiency of 81.3%. The as-prepared metal powder could be readily flushed and collected from the cell with water. This mass transport-enhanced approach may serve as a promising alternative to overcome the drawbacks of existing metal recovery and water purification.

Rate effects on transformation kinetics in a metastable austenitic stainless steel

In this study, the effects of strain rate on the mechanical properties and the strain-induced austenite-to-martensite transformation in type 201 austenitic stainless steel (SS201) were investigated. This grade was selected as a low-cost stainless steel with good lightweighting potential for automotive applications. The material was tested in tension at a quasi-static rate (5×10-2 s-1), two low-intermediate rates (100 s-1 and 101 s-1), and a high rate (5×102 s-1). 3D digital image correlation was used to enable accurate strain measurements during mechanical testing. Magnetic induction and X-ray diffraction were used ex-situ of deformation to measure the volume fraction of martensite formed at each strain rate, for different plastic strain levels. The effects of strain rate on deformation-induced martensite formation and on the stress/strain behavior was determined in this study, and was compared to results reported in the literature for 300 series austenitic stainless steels. The results show a favourable response for the SS201, which exhibits a substantial increase in strength and energy absorption at high rates without compromising tensile ductility.

Controlled Electrodeposition of Uniform Copper Powder from Hydrochloric Acid Solutions

Recovery of copper from hydrochloric acid solution is of significant importance for the heavy-metal pollution protection and valuable metal resources utilization. In order to overcome the drawbacks of low current efficiency and contaminated deposits in conventional electrochemical recovery, a controlled electrodeposition process was first developed using low-cost stainless steel cathodes. It has been demonstrated that mass transport has a facilitating effect for the copper electrodeposition in HCl media, thus a cylinder turbulent cell equipped larger surface area cathode was used. 93.6% copper was successfully extracted with a current efficiency of 89.4%, and the impurity of CuCl was completely eliminated. This indicated the low efficiency chloride-mediated pathway was avoided and the regular 2e reduction to metallic copper was greatly improved. Besides, more uniform and fine powder was obtained, which could be readily flushed and collected from the cell with water. This controlled electrodeposition may serve as a promising alternative to overcome the disadvantages of existing metal recovery and water purification.

Characterization and Performance of Proton Conducting Solid Oxide Fuel Cells Manufactured Using Reactive Spray Deposition Technology

Proton conducting solid oxide fuel cells (SOFCs) have received attention as a possible alternative to traditional oxygen anion conducting SOFCs. The reason is existing proton conducting perovskites display ionic conductivity similar to yttria-stabilized zirconia at lower temperatures. Lower operating temperatures alleviate durability issues and open the door for the use of low cost stainless steels in cell construction. This study examines the use of reactive spray deposition technology (RSDT) as a means of producing a low cost, metal supported proton conducting SOFC by directly depositing layer after layer onto a metal substrate and with a no need for additional sintering steps. The deposited materials are characterized using SEM, STEM, and XRD techniques.

Vacuum-sintered stainless steel porous supports for inkjet printing of functional SOFC coatings

Porous metal supports for SOFC applications were produced via conventional powder metallurgy routes—tape casting and high-pressure injection moulding. The supports were sintered in vacuum at different vacuum levels and temperatures. Commercially accessible low-cost stainless steel 430L powder was chosen as source material. The relations between the vacuum sintering temperature and the supports properties were studied. The density and the open porosity distribution of sintered supports were determined by Archimedes’ method, Optical Image Analysis and Hg-porosimetry. The microstructure and the stainless steel grain surface composition evolution were investigated by scanning electron microscope and energy dispersive X-ray spectrometry. direct ceramic inkjet printing (DCIJP) was employed as coating technology for depositing anode (NiO/GDC) and electrolyte GDC coatings. Suspension anode and electrolyte inks were developed in-house and the printing procedure was optimized to produce uniform coatings with thicknesses below 15 µm. The analyses confirmed that the as-produced substrates were suitable to support DCIJP deposited SOFC functional coatings.