Desalination is considered one of the most viable and technically feasible strategies for the production of freshwater from saline solutions (brackish water, seawater and brine). Thousands of membrane and thermal desalination plants operate daily in many countries around the world, with thermal desalination plants being more advantageous especially in areas with cheap energy. Stainless steel is a reliable material choice for thermal desalination plants due to excellent properties such as stability and minimum maintenance requirements. However, corrosion can cause catastrophic failures in stainless steel due to high temperatures and corrosive environments. The purpose of this review is to provide an overview of stainless steel grades (austenitic, super austenitic, duplex, super duplex and hyper duplex) that have been and can be used in thermal desalination and brine treatment applications and discuss their opportunities and challenges. In terms of mechanical properties and corrosion resistance, the grades of stainless steel are compared. Thus, for each grade, an application area is suggested to minimize the possibility of material failure. Furthermore, this review discusses recent trends in stainless steel corrosion control and anti-corrosion materials and methods.

Stainless Steel in Thermal Desalination and Brine Treatment: Current Status and Prospects

In the last decade, it has been common to observe a competition between coatings achieved via physical vapor deposition (PVD) and chemical vapor deposition (CVD) techniques on cutting tools used in machining processes. The tool’s substrate material can immediately condition the coating process selection. However, there are also materials capabe of adapting to any of the coating processes. Hence, the capabilities demonstrated by a given coating when created with one technique or another are usually different due to the intrinsic characteristics of each coating process, such as temperature and stress levels. In this work, to study the machining behavior of a super duplex stainless steel, PVD- and CVD-coated tungsten carbide inserts with different coatings were used in order to identify the wear mechanisms that affect each of the coatings and the workpiece’s surface quality, evaluated through different roughness parameters. The vibration level produced throughout the various tests was also registered in an attempt to associate the type of coating or insert failure with the level of vibrations generated in the CNC (Computer Numeric Control) machining spindle. This allowed us to conclude that the tools coated with TiAlN via PVD showed better wear behavior, as well as creating workpiece surfaces with less roughness. Thus, it was clear that this coating presents strong advantages in the machining of the super duplex stainless steel chosen for this work, being an innovative work due to the combination of materials used and the approach in terms of vibration analysis applied to milling.

https://www.mdpi.com/2079-6412/9/6/392/pdf

Machining GX2CrNiMoN26-7-4 DSS Alloy: Wear Analysis of TiAlN and TiCN/Al2O3/TiN Coated Carbide Tools Behavior in Rough End Milling Operations

Effect of tensile overload on fatigue crack behavior of 2205 duplex stainless steel: Experiment and finite element simulation

Q&P steels possessing a combination of ultra-high product of strength and tensile elongation (PSE) and superior impact toughness was obtained by tailoring the micromechanical deformation ability of retained austenite (RA) and martensite via low-temperature partitioning. Our results indicate that impact toughness is more susceptible to the heterogeneity of mechanical properties of constituent phases than its tensile mechanical properties. Through optimizing the difference between the constituent phases, the impact toughness can be improved significantly by the enhancement of micromechanical deformation ability of tempered martensite (TM) and corresponding alleviation of deformation incompatibility. Simultaneously, high PSE was preserved by using the deformation potential of RA and its transformation-induced plasticity effect. Load–unload–reload (LUR) tests were carried out to characterize the evolution of flow stress components and the influence of partitioning temperatures on the degree of deformation inhomogeneity between constituent phases during plastic deformation. Furthermore, the mechanical properties and micromechanical deformation ability of the constituent phases were quantitatively characterized using the nanoindentation technique, which indicates that degree of incompatible deformation is alleviated for steels partitioned at relatively high temperatures due to the enhancement of the deformation ability of TM. The underlying relationship between the dynamic transformation of metastable austenite based on the Olson and Cohen model, and high PSE was elucidated. As the partitioning temperature increases, the mechanical stability of RA increases, which is attributed to the synergistic effect of carbon partitioning and the improvement of compatible deformation capability of TM and RA, resulting in an excellent combination of concurrent ductility and impact toughness. Based on the above characterization and analysis, further investigation into the fractured morphology of impact and edge notched specimens was carried out to provide a comprehensive understanding of the damage and fracture mechanism, and to reveal the reasons for the improvement of mechanical properties. The nucleation position and propagation path of microvoids and microcracks depend on the deformation compatibility of constituent phases and the morphology of cementite in tempered martensite. The nucleation sites of microcracks and microvoids at the phase interface, due to stress concentration and dislocation pile-ups for incompatibility deformation of constituent phases, are substituted with nucleation sites at fractured cementite in TM with the increasing partitioning temperature.

Enhancement of Impact Toughness Via Tailoring Deformation Compatibility of Constituent Phases in Duplex Q&P Steel with Excellent Strength and Ductility

The microstructure and micromechanical properties of the constitutive phases of a particular duplex stainless steel in various processing conditions have been characterized. Hardness (H), elastic modulus (E) and H/E cartography maps were obtained by using a high-speed nanoindentation mapping technique. Small-scale H and E evolution at different processing conditions has been investigated by statistical analysis of a large number of nanoindentations (10,000 imprints per sample). Two mechanically distinct phases, ferrite (α) and austenite (γ), were deconvoluted from this dataset using Ulm and Constantinides’ method, with the remaining values assigned to a third mechanical phase linked to composite-like (containing α/γ interphase boundaries) regions. These mechanical property phase assessments were supplemented by overlaying crystallographic phase maps obtained by electron backscattered diffraction. An excellent correlation between microstructure and small-scale mechanical properties was achieved, especially when considering the ratio H/E.

Novel Mechanical Characterization of Austenite and Ferrite Phases within Duplex Stainless Steel

The stress-strain behavior of ferrite and austenite in a commercial 2205 duplex stainless steel was investigated by using nanoindentation test and microstructure-based finite element method (FEM). Results showed that the optimum load range for measuring phase properties in nanoindentation test was from 3000 μN to 7000 μN. The ferrite has slightly higher average elastic modulus than austenite, while austenite has higher average nanohardness than ferrite. Representative stress-strain curves of ferrite and austenite were determined by means of the power-law hardening and empirical relationship. Based on FEM, the differences in distribution and portion of stress-strain in local phases were visualized, and the overall flow curve of the sample 2205 was extracted, which was in good agreement with the obtained results from uniaxial tensile experiment.

Characterization on stress-strain behavior of ferrite and austenite in a 2205 duplex stainless steel based on nanoindentation and finite element method

Yan fei Wang

Papers

Characterization on stress-strain behavior of ferrite and austenite in a 2205 duplex stainless steel based on nanoindentation and finite element method