316L Material Research Articles

Optimization of processing parameters of cold metal transfer joined 316L and weld bead profile influenced by temperature distribution based on genetic algorithm

Austenitic stainless steel alloys find the wide range of application in modern industries like pipework, containers, food production and in medical industries for its excellent processing properties and corrosion resistance. There is enormous literature report on the mechanical properties, appropriate joining of materials using different fusion welding processes. Consequently, the cold metal transfer technique appears to weld materials with low heat input which is a noticeable feature of this welding process. In this paper, cold metal transfer welding is performed on austenitic stainless steel material 316L and its bead geometries such as reinforcement height, depth of weld penetration and bead width profile are examined. The temperature distribution at the welding line is observed by means of the data acquisition unit. Genetic algorithm based optimization technique is used to achieve the desired combination of input variables and weld bead geometry. This developed genetic algorithm optimizes the welding process parameters and geometry of the weld bead, by minimizing the least square error based objective function. The investigation outcome of this paper provides an insight into the characterization of the weldment, the effects of weld current and weld travel speed on temperature profile and mechanical properties include hardness, tensile and residual profiles.

<i>Cocos nucifera</i> Surfactant Performance on Stainless Steel in Hcl and H<sub>2</sub>SO<sub>4</sub> Solutions

The corrosion inhibition effect of Cocos nucifera (CN) surfactant inhibitor, has been inspected on 316L steel in 5 M HCl and H2SO4 solutions by weight loss (WL) method. The results revealed that the presence of alkanols, glycosides, steroids and terpenoids in CN surfactant supported the inhibitor by retarding corrosion effect to give an optimum inhibition efficiency of 93.71% in HCl and 89.66% in H2SO4 solutions after 504 h. Also, the regression values for both acidic solutions were close to unity after obeying Langmuir isotherm adsorption mechanism with 0.9971 for HCl and 0.9882 for H2SO4 solution. The result confirms that CN surfactant inhibitor performed better in HCl solution than in H2SO4 solution. Keywords: Corrosion inhibitor; active components; austenitic 316L material; weight loss method; adsorption isotherm.

Effects of WC particles on microstructure and mechanical properties of 316L steel obtained by laser melting deposition

Stainless steel has many excellent characteristics such as high strength, weldability, corrosion resistance, easy processing and surface gloss. It has been widely applied in many industrial and architectural decoration aspects such as aerospace, chemical, and automotive. However, 316L material manufactured by Laser melting deposition has poor wear resistance and tensile strength. In this paper, WC particles are used as a strengthening phase to make up for these deficiencies of 316L. In order to comprehensively evaluate the effect of WC particles on the mechanical properties of 316L formed by laser melting deposition, 316L samples with different proportions of WC particles and different fabricating directions were prepared. The microstructure of samples was observed, and the phase composition, Vickers hardness, friction and wear properties, tensile properties were analyzed. The mechanism of the influence of WC particles on the structure and the mechanism of friction, wear and tensile fracture were studied. The results show that most of the WC particles are evenly distributed in the coating. The microhardness and wear resistance of the 316L/WC composite coating have been significantly improved with the increase in the proportion of WC. The tensile strength and elongation are the best when the WC mass fraction is 6%.

Effect of chromium–titanium on corrosion and erosion of HVOF coating

ABSTRACT The high-velocity oxyfuel spraying (HVOF) method was used to coat Fe–Cr–Ti-based coating material Fe60Mo5C15Si10Cr0Ti10, Fe50Mo5C15Si10Cr10Ti10, Fe50Mo5C15Si10Cr10Ti0 on base material 316L stainless steel. A comparative analysis was performed to investigate the effect of alloying element chromium and titanium on corrosion and erosion properties of Fe–Cr–Ti coating material. NaCl solution (3.5 wt.) was used for the study of corrosion behaviour. The steady-state erosion wear was examined by varying parameters such as impact speed and impact angle. It was found that the micro-hardness and fracture toughness of Fe–Cr–Ti coating material with 10 wt-% titanium were 18.02 and 5.08% more than those of the coating material with 10 wt-% chromium, respectively. This showed that titanium played a more significant role than chromium in terms of mechanical and erosion properties and a less significant role in terms of corrosion behaviour. Fe50Mo5C15Si10Cr10Ti10 indicated the least wear and a smooth surface with very few pores and wear scars.

COMPUTATIONAL STUDY OF EVOLUTION AND FATIGUE DISPERSITY OF MICROSTRUCTURES BY ADDITIVE MANUFACTURING

In order to predict the correlation among the processing parameters, microstructures, and mechanical properties for additive manufacturing, a computational framework integrating discrete element method, phase-field simulation, crystal plasticity finite element method, and extreme value statistics is proposed. The framework is applied to reveal the influence of laser scanning velocity on the microstructure evolution, yield stress, fatigue indicator parameter (FIP) distribution, and fatigue dispersity, in order to show its capability in simulating additive manufacturing process and the resultant mechanical properties. Firstly, discrete element method simulations are carried out to spread the powder bed layer by layer with the consideration of powder size distribution. The spreading is performed on the curved surface of the previously solidified layer. Secondly, the heat-melt-microstructure coupled non-isothermal phase-field simulations are performed to obtain the temporal and spatial evolution of melt, pore, grain boundary, grain distribution/orientation, etc., as well as the final polycrystal microstructure. Thirdly, crystal plasticity finite element method is utilized to attain the macroscopic mechanical response and stress/strain distribution of the additively manufactured polycrystal microstructure (AMPM) and FIP which is a surrogate measure for the driving force to form fatigue cracks. Fourthly, extreme value statistics are carried out to analyze the extreme value distribution of FIPs and the fatigue dispersity of the AMPM. Comprehensive simulations are put into practice for the selective laser melting based additive manufacturing of a typical metallic material 316L stainless steel. The simulation results indicate that the macroscopic yield stress of the AMPM is anisotropic and decreases with the increasing laser scanning velocity. The extreme value of FIPs from the AMPM with random distribution of grain orientations correlates well with the Gumbel extreme value distribution. The increase of laser scanning velocity could decrease the fatigue dispersity of the AMPM, but increase the FIP extremum and the associated driving force for fatigue crack initiation and thus notably decrease the fatigue life.

FUNDAMENTAL INVESTIGATIONS ON THE MACHINABILITY OF ADDITIVELY MANUFACTURED MULTI-MATERIALS

Additively manufactured multi-materials promise unique combinations of different material properties. However, the machining behavior of these materials is widely unknown. In this study, fundamental investigations on chip formation and morphology, cutting force, workpiece temperature after cutting and surface quality were conducted in orthogonal cutting experiments. Additively manufactured test specimens made out of 316L stainless steel processed by Laser Powder Bed Fusion (LPBF), and the nickel-based alloy Inconel 718 processed by wire-based Laser Metal Deposition (LMD-w) were machined. Investigations were conducted with single- and multi-material combinations as well as porous 316L material. Besides, conventional cast material was machined in order to draw a relative comparison. The results showed significant changes in chip formation and cutting forces between cast and additively manufactured materials, especially for Inconel 718. These differences can be attributed to the changed microstructure and material properties. For two-component multi-materials, the connection area between the materials acted as a defect only to a limited extent. It was shown that the main influence evoke from the cutting direction in relation to the build-up direction of the specimen.

Immersion Ultrasonic Testing of Artificially Induced Defects in Fused Filament Fabricated Steel 316L.

Fused filament fabrication (FFF) with the use of metal-polymer filaments offers a cost-effective solution in additively manufacturing metal parts. Nevertheless, the quality and dimensional characteristics of the FFF produced parts needs to be assured. This short communication reports results and findings from an ongoing investigation on the use of immersion ultrasonic testing (IUT) for the detection of defects in FFF metal parts. In this work, the BASF Ultrafuse 316L material was used with an FFF 3D printer to produce a test specimen for IUT inspection. Two types of artificially induced defects were examined: drilling holes and machining defects. The obtained inspection results are promising in terms of the capability of the IUT method to detect and measure the defects. It was found that the quality of obtained IUT images is not only probe frequency dependent but also sensitive to the part characteristics, indicating a need for a wider range of frequencies and more accurate calibration of the system for this material.

Fatigue crack growth in IN718/316L multi-materials layered structures fabricated by laser powder bed fusion

Multi-materials additive manufacturing (MMAM) allows the functional optimisation of components by tailoring the addition of alloys at different design locations in a single operation. In this study Laser Powder Bed Fusion (L-PBF) technique was used to manufacture layered specimens combining IN718 and 316L materials. The microstructure and mechanical properties were studied by scanning electron microscopy (SEM), tensile, micro and nanohardness testing. The fatigue tests were performed to determine the crack propagation process through multi-layer specimens in the as-built (AB) state.

Simulation Analysis of Additive Manufacturing of Impeller

An Impeller is the rotating component of a pump; it transfers the energy from the motor to the fluid and accelerates the fluid to build up pressure. Impellers are manufactured using Additive Manufacturing (AM) technology. It is a technology that produces three-dimensional parts layer by layer from a variety of materials such as plastics, polymers and metals. The impeller is usually made up of Stainless Steel 316L, Inconel 718. AM technique used to manufacture impeller is Direct Metal Laser Sintering (DMLS). The main objective of this paper is to conduct simulation analysis of additive manufacturing of an impeller by varying process-parameters such as Power, Wall-thickness and Angle and recommend a suitable material with minimum von-misses stress, minimum displacement and minimum of maximum temperature using Amphyon software. Simulation analysis is performed on two different materials i.e., Stainless Steel 316L and Inconel 718 by varying process parameters such as Power at 200 to 400W, Wall thickness at 0.5 to 0.8mm and Angle at 00 to 60. Amphyon is a modular pre-processing and simulation software for Laser Beam Melting (LBM) processes. The simulation results were analyzed and optimization for Stainless-Steel 316L material impeller was done using one of the MADM methods i.e., Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method. Later, the results of the two different materials (i.e., Stainless Steel 316L and Inconel 718) were compared. Stainless Steel 316L was found to have minimum von-misses stress, minimum displacement and minimum of maximum temperature at 200W power, 0.5mm wall-thickness and 00 angle. Index Terms: Impeller, Additive Manufacturing, Direct Metal Laser Sintering (DMLS), Amphyon, MADM, TOPSIS.

Finite element analysis of artificial hip joint implant made from stainless steel 316L

Background: AISI 316L stainless steel material is one of the widely used hip joint implant material. Even with excellent properties for the hip joint implant, this material is likely to fail after 12-15 years of implantation because of excessive wear and stresses. The computational analysis using the finite element method can be used to analyze the stress in the hip joint implant. The study aims to evaluate the stresses and safety factors analysis on the hip joint implant using four different types of AISI 316L materials from several manufacturers are highlighted as the objective of this study.Method: There are four different types of AISI 316L materials used in this study, which are manufactured with different methods. These materials are simulated into Diponegoro University's artificial hip joint design. The ASTM F2996-13 and ISO 7206-4 are considered standard references in the simulation for loading and boundary condition application.Results: Based on the static structural analysis, the total deformation, equivalent elastic strain, equivalent von-Mises stress, and the safety factor are obtained from Undip hip joint implant design.Conclusion: The analysis concludes that the four types of stainless steel materials are safe for UNDIP hip joint implants, which have >1 safety factor. The highest safety factor is obtained from the forging material but has a high manufacturing cost that needs to be optimized.

Mechanical behavior of additively manufactured and wrought 316L stainless steels before and after neutron irradiation

Fabrication of nuclear reactor components using additive manufacturing (AM) methods is now a practical option since the AM technologies have advanced to allow for building of complex parts with high quality materials. To assess the mechanical performance of printed components in reactor-relevant conditions and to build a property database for the AM 316L stainless steel (SS), mechanical testing and characterization were performed before and after neutron irradiation. Miniature tensile specimens were irradiated at the High Flux Isotope Reactor (HFIR) to 0.2 and 2 displacements per atom (dpa) at 300 and 600°C. The AM 316L SS was tested in the as-built, stress-relieved, and solution-annealed conditions, and the wrought (WT) 316L SS in solution-annealed condition as a reference alloy. The baseline test result showed that the AM 316L SS, regardless of the post-build heat treatment, had higher strength than the WT 316L SS, but similar ductility. Post-irradiation tensile testing was conducted at RT, 300°C, and 500°C for selected irradiation conditions. Neutron irradiation induced significant changes in the mechanical behavior of the AM stainless steels, including both hardening and softening. Although the as-built 316L steel after 300°C irradiation showed necking just after yielding, the overall property changes of the as-printed alloy became less significant after 600°C irradiation. Irradiation-induced ductilization was also observed after the higher temperature irradiation. In general, the strength change was smaller in the relatively stronger as-built and stress-relieved AM SSs than in the solution-annealed AM and WT SSs. These relatively lower strength 316L SSs overall retained higher ductility in the irradiation conditions tested, but the stronger 316L SSs demonstrated a similar level of ductility after the higher temperature (600°C) irradiation. It is a positive assessment for the AM 316L materials that no embrittlement was observed within the test and irradiation conditions of the experiment.

Experimental and numerical investigation on lattice structures fabricated by selective laser melting process under quasi-static and dynamic loadings

Lattice structures are a class of cellular materials with greater control over the mechanical properties, relative to other common cellular materials like foams and honeycomb structures. In this paper, three lattice structures including Kelvin, Rhombic dodecahedron, and truncated cuboctahedron with identical geometric dimensions in quasi-static and dynamic loadings were investigated to identify the proper lattice structure for impact resistance applications. This study consisted of two experimental and numerical sections. In the experimental section, the lattice structures were fabricated using the selective laser melting (SLM) method from the AISI 316L material. The dynamic tests of the lattice structures were performed by the split Hopkinson pressure bar (SHPB) with a strain rate of 765 s−1. In the numerical section, the modeling was carried out by the finite element method (FEM) to predict the properties of the lattice structures. The results of the experimental tests showed that the selected lattice structures had a high strength to weight ratio and considerable impact resistance; so, they could be suitable for use in lightweight and impact-resistant structures. In addition, the modeling results revealed a good agreement with the experimental results. Finally, the specific absorbed energy of the Rhombic dodecahedron lattice structure in the quasi-static compression test and with the 50% strain was 7% and 15% higher than that of Kelvin and truncated cuboctahedron lattice structures, respectively. While, with evaluation of the dynamic results, the truncated cuboctahedron lattice structure had higher area under the specific stress-strain curve in comparison to the other two structures.

SENSITIVITY ANALYSIS OF STAINLESS STEEL REFLECTOR FOR VR-1 TRAINING REACTOR

Pressurized water reactors are typically surrounded in the radial direction by neutron reflectors made from stainless steel and water. These reflectors decrease neutron leakage and provide protection of pressure vessel from fast neutrons damaging its integrity. Such a radial reflector influences multiplication factor of the core and distribution of neutron flux and fission power inside the core. All these effects can be analyzed by full-core simulations using macroscopic constants. Methodology for generation of the macroscopic constants for non-fuel regions will be tested for new stainless steel reflectors at the VR-1 reactor. Rods from SS 304l material will be used for construction of radial reflectors for the VR-1 reactor. They will be design to generate sufficient measurable response in selected core characteristics. The study is focused on core power distribution and reactivity worth of absorbing rods in a VR-1 reactor core. The core typically consists of about 20 IRT-4M fuel assemblies and seven absorbing rods UR-70. Replacing water surrounding the core by several reflector assemblies containing stainless steel will influence leakage and distribution of neutrons inside the core. The current analysis deals with local effects and employs the sensitivity study to discover the nature of reflectors’ impact on the reactor core. These effects were studied even for several past VR-1 reactor core configurations. All calculations were carried out in Serpent2 Monte-Carlo code with various evaluated libraries: ENDF/B-VII.1, ENDF/B-VIII.0, and JEFF-3.3 data.

Effects of Heat Treatment on the Microstructure and Mechanical Properties of Selective Laser Melting 316L Stainless Steel

316L stainless steel materials are widely used in impact‐resistant structures. Heat treatments could affect the mechanical properties of 316L stainless steel parts formed by selective laser melting (SLM), which is vital for ensuring service safety. This study aimed to analyze the mechanical behavior of SLM 316L stainless steel under different heat treatment methods. Therefore, test specimens were prepared using the SLM technique and then annealed at 400°C for 1 h. The solution was treated at 1050°C for 20 min. The dynamic compressive mechanical properties of the deposited, annealed, and solution‐treated specimens were tested at high strain rates by using a split Hopkinson pressure bar (SHPB) experimental apparatus. Moreover, the microstructures of the previously mentioned samples were analyzed by optical microscopy and scanning electron microscopy. The experimental results showed that the three‐state samples exhibited strain rate sensitivity in the dynamic mechanical tests and that solution treatment could alter their mechanical properties significantly. In addition, the microstructure of the deposited specimens presented cylindrical cellular crystal features, which have a higher dislocation density. Hence, the yield strength of deposited specimens is higher than that of the solution‐treated ones. After annealing, the microstructures of the samples did not change obviously, and their dynamic yield strength remained almost unchanged. After solution treatment, its cellular crystal disappeared and dislocation density dropped dramatically, resulting in a sharp decrease in yield strength. Finally, this research can provide a theoretical reference for broadening the practical application of SLM 316L material parts.

Characterization of tool wear in i-FSW of AISI 316L material joining

The i-FSW performed by using Nichrome coil pre-heating to the specimen dimension 100 × 75 × 2 mm of AISI 316L material to achieve the desire temperature and make successful friction stir welding. The experiment conducted on conventional milling machine by using TWC tool , whereas the pin length is 1.6 mm and pin diameter is 2.8 mm. The range of spindle rotation 600, 800 & 1000 revolution per min with welding speed of 15, 20 & 25 mm/min. The induction coil set inside the base plate and insulated with Fiber Glass Tape. The pre-heating temperature achieved 120°Celsius, which slightly increase the heat affected zone but also reduce the heat stresses inclusion. The additional heat source provide enough heat energy to produce fine grain size and achieve maximum strength of the weld joint. The experimentation has proved that the i-FSW welding of AISI 316L material is successful and pre-heating of specimen reduces the tool wear of 40% in comparison with normal FSW of specimen. The maximum mechanical properties such as UTS achieved 504 N/mm2 with 97% welding efficiency.

Prevention study on defective solid expandable tubular fracture

This study aims to reveal the failure mechanism of solid expandable tubular (SET) in a laboratory experiment and avoid downhole application failure. The scanning electron microscope (SEM) test of the section is carried out, and the finite element model of the defective expandable tubular is established. It was found that the tube defect causes the rupture failure of the expansion tube in the laboratory experiment, and the failure with defects in the inner wall occurs mostly. The safety and reliability of metal materials 316L and 304 are better than 20G and SA106b. Flaw detection shall ensure that the tube wall thickness is larger than 3.6 mm at any position. Moreover, rubber rings number and defect length have little effect on the bulging performance. The results provide a theoretical basis for preventing the fracture of SET.

Microstructure and mechanical properties of similar and dissimilar joints of RAFM and 316L by electron beam welding

Abstract 316L is a structural material used in fusion reactor vacuum vessels (VVs), in-vessel component supports, and cooling pipes, while reduced-activation ferritic/martensitic (RAFM) steel is the structural material used in test blanket modules (TBMs). High-energy electron beam welding is a suitable method for welding RAFM/316L joints. To explore the electron beam welding process of RAFM/316L, 150 kV/39 mA are chosen as the welding parameters to connect the dissimilar materials, and the microstructure and mechanical properties of the joint are tested and analyzed after welding. The results demonstrate a magnetic deflection of the 316L/RAFM welding joint due to phase change. Thus, an electron beam shift is made to compensate for this deflection. Microstructural observations indicate that the weld metal (WM) of RAFM/316L comprises lath martensite and a small amount of ferrite. The RAFM heat-affected zone (HAZ) of RAFM/316L can be divided into three regions: a fusion zone comprising coarse ferrite and martensite, a completely quenched zone comprising quenched martensite, and an incompletely quenched zone comprising eutectic ferrite and quenched martensite. Mechanical property test results indicate that the WM of RAFM/316L is better than the 316L base material and WM of 316L/316L in terms of tensile strength, and the top of the RAFM/316L joint is comparable to, but with a weaker bottom, than that of the 316L and RAFM base materials in terms of impact toughness.

Out-gassing measurement of air-baked SS 304L material by pressure-rise method

Abstract Out-gassing measurement of air-baked 2∇ surface finished SS 304L material was carryout by pressure-rise method. This material was neither polished nor chemically treated before measurement. The surface was water cleaned to remove the oil contamination and then dried with dry air. The outgassing of this material was found to be ≤ 10−15 mbar l/s/cm2 even after long exposure to atmospheric condition.

Influence of the Miniaturisation Effect on the Effective Stiffness of Lattice Structures in Additive Manufacturing

Thin-walled and cellular structures are characterised by superior lightweight potential due to their advantageous stiffness to weight ratio. They find particular interest in the field of additive manufacturing due to robust and reproducible manufacturability. However, the mechanical performance of such structures strongly depends on the manufacturing process and resultant geometrical imperfections such as porosity, deviations in strut thickness or surface roughness, for which an understanding of their influence is crucially needed. So far, many authors conducted empirical investigations, while analytical methods are rarely applied. In order to obtain efficient design rules considering both mechanical properties and process induced characteristics, analytical descriptions are desirable though. Available analytical models for the determination of effective properties are mostly based on the simple advancement of beam theories, mostly ignoring manufacturing characteristics that, however, strongly influence the mechanical properties of additive manufactured thin-walled structures. One example is the miniaturisation effect, a microstructural effect that has been identified as one of the main drivers of the effective elasto-plastic properties of lightweight structures processed by additive manufacturing. The current work highlights the need to quantify further microstructural effects and to encourage combining them into mesostructural approaches in order to assess macrostructural effective properties. This multi-scale analysis of lattice structures is performed through a comparison between effective stiffness calculated through an analytical approach and compression tests of lattice structures, coupled with an investigation of the arrangement of their struts. In order to cover different potential loading scenarios, bending-dominated and stretch-dominated lattice structures made of the commonly used materials 316L and Ti6Al4V are considered, whereby the impact of microstructural phase transformation during processing is taken into account.

Influence of the heat treatment on the surface bioactivity of investment cast SS 316L

In present paper, an attempt has been made to assess the effect of solution annealing on investment cast stainless steel 316L (Low carbon) material’s tensile strength, microstructure and also to assess surface bioactivity of heat treated SS 316L. Solution annealing at 1020 °C dissolved sigma phase into austenite matrix and also reduces ferrite phase by 83.36%, which result into negligible magnetism. Further investigation has been carried out by in-vitro testing, to assess surface bioactivity. It has been observed from SEM and EDX analysis that heat treated SS 316L has apatite formation ability, a compatibility with body fluid.