Duplex Stainless Steel Research Articles

Development of Thermodynamic Criteria for Determining the Composition of Duplex Stainless Steels with High Corrosion Resistance.

One of the most popular methods for ranking duplex stainless steels (DSSs) and predicting their corrosion properties is the calculation of the pitting resistance equivalent number (PREN). However, since DSSs are two-phase materials with a significant fraction of secondary phases and precipitates, the application of the PREN can be highly limited. This article attempted to use a new approach to describe the corrosion resistance of these steels. The corrosion resistance of two DSSs of the same class was investigated. Under identical solution heat treatments in the temperature range of 1050-1200 °C, the crevice corrosion resistance of one steel increased, while that of the other decreased. It was demonstrated that the amounts of austenite and ferrite changed similarly in these steels, and the different corrosion resistances were associated with the behaviors of secondary phases: niobium carbonitride and chromium nitride. SEM-EDS analysis was conducted to analyze the redistribution of elements between phases in both cases, showing good agreement with the thermodynamic modeling results. The PREN was calculated for each phase depending on the treatment temperature, and a method for calculating the effective PREN (PRENeff), accounting for phase balance and secondary phases, was proposed. It was shown that this indicator described corrosion properties better than the classical PREN calculated for the average steel composition. This study demonstrated how the calculation of critical temperatures (the temperature of equal amounts of ferrite and austenite, the temperature of the beginning of chromium nitride formation, and the temperature of the beginning of σ-phase formation) could describe the corrosion resistance of DSSs. Maximum possible deviations from these temperatures were defined, allowing the attainment of the required corrosion properties for the steels. Based on the conducted research, an approach for selecting new compositions of DSSs was proposed.

Microstructure Formation and Its Effect on Mechanical Properties for Duplex Stainless Steel 2205 Plasma Arc Welded Joint

The control of phase balance has always been a tough challenge for the welding of duplex stainless steel, which heavily restricts its optimal serving performance in engineering. The microstructure development and mechanical characteristics of SAF2205 plasma arc welded joints were thoroughly examined in this paper. It was proven that the phase balance can be well controlled by plasma arc welding, and the austenite content of the welded joints was about 60%. Despite successful phase control, there was still grain coarsening and distortion; i.e., at the center of the welded zone, the gain size was about eight times that of the base metal, and the austenite was mainly in the form of grain boundary austenite and intragranular austenite, while more Widmanstatten austenites were found in the heat-affected zone. In addition, a transition region between the heat affected zone and the center exhibited columnar ferritic grains. Furthermore, the plasticity and toughness of the welded joints were significantly decreased, especially the elongation in the longitudinal direction, which is about 10% lower than that of the base metal, and transversal tensile strength remained comparable to the base metal, with only a slight reduction in longitudinal tensile strength. Lastly, the formation mechanism of microstructure and its correlation with mechanical properties were revealed. This investigation offers valuable insights into the structural integrity of duplex stainless steel welded joints in engineering applications.

Tuning hatch distance to optimize microstructure and mechanical properties of 2205 duplex stainless steel produced by laser powder bed fusion

Laser powder bed fusion (LPBF) of duplex stainless steel is a promising route to fabricate intricate parts with excellent mechanical properties. However, further understanding of build mechanisms is required to improve the process. This paper aims to better understand the influence of hatch distance on the densification behavior and figure out the correlation with microstructure and mechanical properties in LPBF of 2205 stainless steel. With the optimized laser power and scanning speed, the significant influence of hatch distance on the build quality is revealed. A hatch distance of 0.07 mm is selected for an even surface and dense part with a relative density of up to 99.13 %. The hatch distance has a crucial impact on the heat and mass transfer between tracks; hence, poor surface morphologies such as inter-track voids or swelling surfaces occur if an improper hatch distance is adopted. The optimal mechanical properties are also achieved. Specifically, the yield strength (0.2 YS), ultimate tensile strength (UTS), and elongation (EL) values are 896.8 MPa, 1035.13 MPa, and 15.34 %, respectively. The improvement in mechanical properties can be ascribed to the coordination between high dislocation density, fine grain size, high CSL boundaries and LAGBs, and high relative density with few pores. This work can help improve the build quality and expand the application horizon of duplex stainless steel for manufacturing intricate components.

Effect of elastic tensile stress on the pitting corrosion mechanism and passive film of 2205 duplex stainless steel

The effects of elastic tensile stress on the pitting corrosion mechanism and passive film of 2205 duplex stainless steel (DSS) in an NaCl solution containing sulfide ions are investigated. The results reveal that as the elastic tensile stress increases, the pitting corrosion sensitivity of 2205 DSS first decreases and then gradually increases, which is attributed to the changes in the chemical state, thickness, and micro-defects of passive film. Furthermore, the initial pits occur at the austenite phase under low elastic stress but at the ferrite phase under higher elastic stress. The corrosion pits grow rapidly along the pit bottom direction and the perpendicular direction of tensile stress.

Effect of preheat in DED-LB/wire of Ni-base, Cu-base and Fe-base alloys

Preheating of welding wire by electric current is an established technique for increasing deposition rate during welding, but is a relatively new contribution to additive manufacturing. The few studies that have been performed for additive methods have focused on a limited selection of materials, typically only one material grade, which limits their relevance to other material grades. This study has investigated the effect of resistive wire preheating, also known as hotwire, in a coaxial directed energy deposition system with laser beam and wire (DED-LB/wire), across a wider range of material grades so that effects of hotwire on different alloy compositions and crystal lattice structures can be determined. Inconel 625, aluminium bronze, nickel-aluminium bronze, carbon steel, austenitic, martensitic and duplex stainless steels were examined to provide a sampling of Ni-, Cu- and Fe-based alloys, as well as a comparison of austenitic, martensitic and duplex stainless steels.

Effect of build orientation and heat treatment on the microstructure, mechanical and corrosion performance of super duplex stainless steels fabricated via laser powder bed fusion

Build orientation in PBF-L manipulates microstructures, thus tuning the mechanical and corrosion properties of duplex stainless steel before and after heat treatment.

Effect of laser defocusing on duplex stainless steels for higher scan speeds in Laser-Based Powder Bed Fusion (PBF-LB/M)

Duplex stainless steels (DSS) employ a bi-modal microstructure consisting of equal parts ferrite and austenite. However, when processed via laser-based powder bed fusion (PBF-LB/M) the high cooling rates lead to a dominantly ferritic microstructure, thus making a post-process heat treatment necessary. This sparks the interest in accelerating the manufacturing time by increasing scan speeds. Defocusing of the laser beam offers the possibility to alter the melt pool morphology and thereby the melting mode. Therefore, this study presents the influence of the defocusing distance for PBF-LB/M manufactured DSS parts. The melt pool becomes shallower and wider as the defocus distance increases, but also has a more uniform shape at high scan speeds compared to the focused beam. Furthermore, defocusing of the laser beam results in denser parts at scan speeds of up to 1800 mm/s, potentially facilitating higher build rates. The duplex microstructure could be restored by a post process heat-treatment.

A Study On Stress Management Among Employees Towards Alloy Industries With Reference To Coimbatore

In order to boost strength or corrosion resistance, two or more metallic components are mixed to form an alloy, which is a type of metal. A metallic material composed of two or more elements is called an alloy, sometimes known as a compound or a solution. Although the non-metal carbon is an essential part of steel, the constituents of alloys are normally metals. Alloys are often created by melting the mixture of components. According to customer specifications and drawings, Alloys Industries manufactures and exports a variety of machined and un-machined castings made of Carbon Steel, Stainless Steel, Low Alloy Steel, Heat Resistant Steel, Martensitic Stainless Steel (CA6NM), Precipitated Hardened Steel (CB7Cu-1), Nickel Alloy, and Duplex Stainless Steel. The phrase "stress managements" is broad and includes training, facilitation, and education about the effects that stress has on an individual or group. The study of stress management fosters and encourages the development of coping mechanisms. Employees' physiology and psyche are stressed out by organisational elements such management-labor relations, working conditions, resource distribution, the role of trade unions, employee behaviours, etc. The working practises and policies of an organisation are among its most important influencing variables. This study examined the occupational stress experienced by Alloy Industries in Coimbatore, employees in great detail.

Transformation of inclusions in S32101 duplex stainless steel during continuous casting

In this study, the formation and characteristics of inclusions in S32101 duplex stainless steel (DSS) during continuous casting were investigated by analyzing inclusions in the tundish and continuous casting slabs. The composition of inclusions changed significantly during the continuous casting. The inclusion type in the tundish was primarily CaO-SiO2-Al2O3-MgO-MnO. There are two types of inclusions in the continuous casting slab: CaO-SiO2-Al2O3-MgO-MnO inclusions with dense Al2O3 and MnO, and Al2O3-MnO inclusions. TiN wraps the outer layers of both types of inclusions. The results obtained from thermodynamic calculations agreed with the experimental results. The weight percentage of Al2O3 and MnO in the inclusions increases significantly with the solidification process. In addition, the Al2O3-MnO inclusions were formed in the slab. TiN precipitates during the solidification of the S32101 DSS. The CaO-SiO2-Al2O3-MgO-MnO and Al2O3-MnO inclusions can be used as the nucleation sites of TiN.

Impact of process parameters and gas atmospheres on density and microstructure of super duplex stainless steel produced by Laser Powder Bed Fusion

Super duplex stainless steel (2507 SDSS) is an alloy renowned for its excellent corrosion resistance and mechanical properties. This unique combination arises from a duplex microstructure characterized by austenite and ferrite. However, when processed using the laser powder bed fusion (LPBF) process, this steel contains only the ferritic phase due to the rapid cooling rates inherent in LPBF, which suppresses the formation of the austenitic phase. This study explores a parameter process optimization for this steel in two different atmospheres, Ar and N, with the latter being an austenite-stabilizing element intended to enhance the formation of the austenitic phase. A comparison of the optimal process windows between the two atmospheres is conducted, and the amount of austenitic content is evaluated as a function of the process parameters and the shielding gas employed. Findings demonstrate that utilizing a nitrogen atmosphere, in conjunction with process parameters that reduce normalized enthalpy and material evaporation, increases austenite content post-manufacture. Additionally, nitrogen as the processing gas effectively minimizes and stabilizes nitrogen content within the samples.

Machinability investigation of S32750 super duplex stainless steel using magnetorheological fluid-assisted nano polished cemented carbide tool inserts

Machinability investigation of S32750 super duplex stainless steel using magnetorheological fluid-assisted nano polished cemented carbide tool inserts

Numerical and experimental studies of thin super duplex stainless steel GTAW joints

Numerical and experimental studies of thin super duplex stainless steel GTAW joints

Suppressing fatigue crack growth owing to welded joints of duplex stainless steel subjected to multiple high-density pulsed electric currents

Suppressing fatigue crack growth owing to welded joints of duplex stainless steel subjected to multiple high-density pulsed electric currents

Machinability investigation of S32750 super duplex stainless steel using magnetorheological fluid-assisted nano polished cemented carbide tool inserts

Machinability investigation of S32750 super duplex stainless steel using magnetorheological fluid-assisted nano polished cemented carbide tool inserts

Experimental Analysis on Turning of Super Duplex UNS 32750 Steel Using Minimum Quantity Lubrication Process

Current production trends necessitate extensive use of cutting fluids, resulting in adverse climatic changes and increasing industry expenses. Modern manufacturing businesses are looking for new ways to meet the demands for faster machining rates, less waste, and improved product quality while also lowering manufacturing costs. Material removal rate (MRR) and surface roughness (SR) of the work piece machined with coated tools are all evaluated. Cutting speed (CS), pressure flow (PF), and depth of cut(DOC), are the input parameters. An aerosol mixture of air and oil was used to give the least amount of lubrication. To assess the relative performance tuning with the MQL setup, an investigation was conducted. When compared to dry turning, the MQL system for turning super duplex stainless steel UNS 32750 has shown to be more effective. The MQL technique significantly improves cutting performance in terms of increasing tool life and improving machined component quality.

Evolution of residual stress and microstructure of 2205 duplex stainless steel welded joints during different post-weld heat treatment

Evolution of residual stress and microstructure of 2205 duplex stainless steel welded joints during different post-weld heat treatment

Sigma Phase Detection in Duplex Stainless Steel Based on Correlation to Current and Potential in Micro Electrode Electrochemical of Surface

Sigma Phase Detection in Duplex Stainless Steel Based on Correlation to Current and Potential in Micro Electrode Electrochemical of Surface

Optimization of duplex stainless steel UNS S32205 end milling with noise factor analysisy

Optimization of duplex stainless steel UNS S32205 end milling with noise factor analysisy

Effect of build orientation and heat treatment on the microstructure, mechanical and corrosion performance of super duplex stainless steels fabricated via laser powder bed fusion

Correction for ‘Effect of build orientation and heat treatment on the microstructure, mechanical and corrosion performance of super duplex stainless steels fabricated via laser powder bed fusion’ by Karl Peter Davidson et al., Mater. Adv., 2024, 5, 8177–8198, https://doi.org/10.1039/D4MA00448E.

Study and Characterization of Sigma Phase in Duplex Stainless Steel 2205 (03Kh22N6M2)

Study and Characterization of Sigma Phase in Duplex Stainless Steel 2205 (03Kh22N6M2)