High Nitrogen Nickel-free Stainless Steel Research Articles

Physical simulation of the heat-affected zone in nickel-free high-nitrogen stainless steel weld at various peak temperatures and cooling rates

Nickel-free high-nitrogen stainless steel (NFHNSS) stands out for its remarkable strength, ductility and toughness making it a preferred choice for applications demanding robust structural integrity. Physical simulations of NFHNSS heat-affected zone under different peak temperatures and cooling rates were studied. Based on the phase diagram simulated from Thermo Calc, physical simulations were carried out on 16 specimens with varying peak temperatures ( 800 °C, 900 °C, 1000 °C and 1250 °C) and various cooling rates (CR) as (25 °C/s, 15 °C/s, 5 °C/s and 2 °C/s). The specimens were grouped and characterised based on peak temperature under varying cooling rates. The microstructural changes, precipitates, hardness and tensile properties of the base metal and heat-affected zone (HAZ), were investigated. HAZ subzones are very sensitive to peak temperature and cooling rate lead to variation in grain size. The test results showed significant refinement in HAZ grain size and significant improvement in strength with a fast cooling rate. Furthermore, transmission electron microscopy analysis showed Cr2N formation with respect to the cooling rate. Yield and tensile strength increased with an increase in CR and ductility reduced slightly. Whereas, with an increase in peak temperature yield strength, tensile strength reduced and ductility increased due to grain coarsening

Effects of nitrogen on predominant sintering mechanism during the initial stage of high nitrogen nickel-free stainless steel powder

Effects of nitrogen on predominant sintering mechanism during the initial stage of high nitrogen nickel-free stainless steel powder

Enhancement of microbiologically influenced corrosion resistance of copper-containing nickel-free high nitrogen stainless steel against marine corrosive Pseudomonas aeruginosa

The antibacterial performance and marine microbiologically influenced corrosion (MIC) resistance of a novel copper-containing nickel-free high‑nitrogen stainless steel (HNS) against marine Pseudomonas aeruginosa were studied. The electrochemical tests indicated that the copper content (0, 2 and 4 wt%) would hardly affect the corrosion resistance of HNS in abiotic simulated seawater. In the presence of bacteria, HNS-4Cu showed the best MIC resistance, while MIC rates of HNS-0Cu and HNS-2Cu were comparatively faster. Addition of 4 wt% copper significantly improved the antibacterial effect and the quality of the passive film of HNS, achieving a better MIC resistance.

Thermomechanical Simulation of Heat-Affected Zones in Nickel-Free High Nitrogen Stainless Steel: Microstructural Evolution and Mechanical Property Studies

Three different Heat Affected Zones (HAZ) in hot rolled Nickel Free High Nitrogen Stainless Steels (NFHNSS) based on three different peak temperatures were physically simulated using Gleeble Simulator to investigate microstructural evolution and structure-property correlation. Optical microscopy revealed that the austenite grains are recrystallized in the simulated heat affected zone in the peak temperature range of 750 oC to 1050 oC. Extent of recrystallization of grains and nucleation of precipitates varied with peak temperatures. TEM characterization showed the presence of Cr2N precipitate having an average particle size in the range of 300 nm to 395 nm in the simulated HAZ were confirmed by Selected Area Electron Diffraction (SAED) analysis. Precipitation kinetics of Cr2N were simulated using Thermo-Calc were found to correlate well with experimental values. Mechanical properties of specimens taken from three different HAZ were evaluated for tensile strength and hardness. Variation in strength of the different specimens has been discussed using various strengthening models. Fractography analysis was also carried out to understand the effect of peak temperature on fracture behaviour. Transition in fracture patterns in NFHNSS from ductile to mixed mode was observed for different specimens.

High‐Nitrogen Nickel‐Free Stainless Steel: An Attractive Material with Potential for Biomedical Application

Metal materials such as stainless steel, cobalt‐based alloy, and NiTi alloy used in clinic contain a certain amount of nickel (Ni) for the structure stability. Nickel ions can gradually dissolve into the human body even with much slow corrosion rate, causing allergic, inflammation, local tissue proliferation, and other adverse reactions to some people. To avoid these adverse effects of nickel, a new high‐nitrogen nickel‐free stainless steel (HNNFSS) using nitrogen and manganese instead of nickel to stabilize the austenite structure is developed, which exhibits much better mechanical properties, good corrosion resistance, and biocompatibility. Compared with the conventional orthopedic metal implants, the adhesion strength of HNNFSS implant with the surrounding tissue in animal is found to be stronger with new bone formation, promoted by both alkaline phosphatase (ALP) and osteocalcin (OCN) expressions. The vascular stent made of HNNFSS shows lower restenosis rate compared with the traditional 316L stainless steel stent, which is attributed to the promotion of endothelial cell and inhibition of smooth muscle cells, and superior blood compatibility. In conclusion, results from large number of studies show that high‐nitrogen nickel‐free stainless steel as a new kind of high‐performance biomedical metallic material possesses great application potential.

EFFECTS OF PULSE WIDTH ON CORROSION BEHAVIOR OF DIAMOND-LIKE CARBON COATINGS PREPARED ON THE SURFACE OF HIGH NITROGEN NICKEL-FREE STAINLESS STEEL

Effects of different pulse widths on morphologies and corrosion resistance of diamond-like carbon (DLC) coatings prepared on the surface of high nitrogen nickel-free stainless steel (HNSS) were investigated. It was found that different pulse widths of 10, 15 and 20[Formula: see text][Formula: see text]s mainly affect the porosity and internal stress within the coatings. The energies of the implantation ions were decreased as the pulse width increase. The growth mechanism of the coating with the pulse width of 20[Formula: see text][Formula: see text]s was mainly surface diffusion, in which the coating was porous and prone to corrosion. With the decrease of pulse width, the growth mechanism was mainly sub-plantation. The DLC coating became dense and the corrosion resistance was improved significantly. However, with further decrease of pulse width, internal stress within the coating was also increased. The effect of stress corrosion cracking may decrease the corrosion resistance of the DLC coating with the pulse width of 10[Formula: see text][Formula: see text]s. The influencing mechanisms of the pulse width on corrosion resistance and growth mechanism of DLC coating on the surface of HNSS are also discussed.

Corrosion Behavior of a Nickel-Free High-Nitrogen Stainless Steel with Hydrogen Charging

Hydrogen permeation usually facilitates the corrosion of stainless steel remarkably. Herein, the corrosion behavior of a nickel-free high-nitrogen stainless steel (HNSS) containing 0.96 wt.% nitrogen with hydrogen charging is investigated by means of electrochemical measurements and x-ray photoelectron spectroscopy surface analysis. The results show that hydrogen charging not only increased the passive current density but also increased the pitting potential of HNSS. The increase in passive current density was attributed to the increased carrier density, depleted Cr content, and decreased O2−/OH− ratio in the passive film, while the increase in the pitting potential resulted from the enrichment of N element in the passive film and the replacement of Ni with Mn in HNSS.

Nickel Free Alloy for Cardiovascular Stents Application Against Restenosis Associated with Nickel: A Review

The commercialized coronary stents are generally made of biomedical stainless steels (316L) and biomedical cobalt-based alloy (for example L605 alloy) due to their good combination of properties, especially their excellent mechanical properties. However, there are above 10% nickel content in these stents materials, which was known to trigger the inflammation and allergic responses around stents implant location, and contradiction associated with in-stent restenosis when the nickel ions began to release from stents for various corrosion. Consequently, the potential adverse effect of nickel ions release has prompted the development of many nickel free alloy stents materials. In this paper, the controversy of nickel and in-stent restenosis, and the development of nickel free alloy for cardiovascular stents application are reviewed. Nickel free cobalt alloy maybe a good choice for stent materials, but further research is needed. Many research results have proved the high nitrogen nickel-free stainless steel is a good potential stents material and suitable for clinical use, therefore the austenitic high nitrogen nickel-free stainless steels may offer an alternative to further improve the performance of the current coronary stents.

Enhancing General Corrosion Resistance of Biomedical High Nitrogen Nickel-Free Stainless Steel by Nitric Acid Passivation

A systematic study of nitric acid passivation was investigated to enhance the general corrosion resistance of biomedical high-nitrogen nickel-free stainless steels (HNSs). After passivation, the corrosion rate of HNS could dramatically reduce to 1/20 of the untreated in 37 °C 0.9 wt% NaCl solutions. Then, the passive film on HNS was analyzed by X-ray photoelectron spectroscopy. It was found that chromium enrichment in the passive film and nitrogen enrichment in the film/metal interface contributed to the improvement in general corrosion resistance of HNS.

Nanoindentation creep deformation behaviour of high nitrogen nickel-free austenitic stainless steel

ABSTRACTNanoindentation tests of the high nitrogen nickel-free austenitic stainless steel (HNS) were performed with peak load in a wide range of 100–600 mN to investigate the nanoindentation creep deformation behaviours. The results of the nanoindentation creep tests have demonstrated that the load plateaus, creep strain rate and creep stress of the cold-rolled HNS are larger and its creep stress exponent is smaller than the solution-treated HNS. The analysis reveals that the obvious creep deformation behaviour in the cold-rolled HNS arises from the rapidly relaxed dislocation structures in the initial transition regime, while the small creep deformation behaviour of the solution-treatedHNS is mainly attributed to that the stable dislocation structures for the intensive interactions between dislocations.

Enhancing general corrosion resistance of biomedical high nitrogen nickel-free stainless steel by water treatment

An extremely simple and environmentally friendly water treatment was developed to enhance the general corrosion resistance of biomedical high nitrogen nickel-free stainless steels (HNNFS). After treatment, the corrosion rate of HNNFS could dramatically reduce to 1/20 of the untreated in 37 °C 0.9 wt% NaCl solutions. Then the passive film on HNNFS was analyzed by electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). It was found that Cr enrichment and thickness increase of passive film contributed to the improvement of general corrosion resistance of HNNFS.

Biomechanical compatibility of high strength nickel free stainless steel bone plate under lightweight design

High nitrogen nickel-free stainless steel (HNNFSS) has excellent mechanical properties, corrosion resistance and biocompatibility, but its strength advantage is not fully used even though with one time higher than that of the conventional 316 L stainless steel. In this work, the lightweight design of HNNFSS bone plate was studied using finite element analysis, and the effect of lightweight plate fixation on histological and biomechanical behavior of healing bone were also researched on fractured rabbit femur. The finite element analysis results showed that the lightweight plate within 18.2% thickness reduction had higher bending strength and more homogeneous stress distribution compared with 316 L stainless steel plate. There was no obvious difference in radiography, histology analysis of callus and expression pattern of insulin like growth factor-1(IGF-1) of callus between the lightweight HNNFSS plate group and 316 L stainless steel plate group in animal test, and the IGF-1 concentrations of callus and the biomechanical bending test results also showed no statistical significance (p > 0.05), even though the data of the lightweight HNNFSS plate group were relatively better than that of 316 L stainless steel plate group. Therefore, the high nitrogen nickel-free stainless steel has the lightweight potential to keep good fixing function and improve bone healing compared with 316 L stainless steel plate.

Synthesis of High-Nitrogen Steel by SHS Reduction with Aluminum

High-nitrogen austenitic steel is characterized by high strength, plasticity, and corrosion resistance. However, its production by traditional methods (under high nitrogen pressure) calls for energy-intensive and complex equipment. In terms of energy conservation, a simpler alternative is the reduction of metal oxides by means of aluminum under nitrogen pressure. The present work is devoted to thermodynamic modeling of such reactions. High-nitrogen nickel-free stainless steels (of Cr–N and Cr–Mn–N type) with around 1% nitrogen are produced by the proposed method. The structure of the steel samples is investigated by X‑ray diffraction, metallography, and transmission electron microscopy; their mechanical properties are also determined. Thermodynamic analysis shows that the reduction processes are incomplete. In synthesis, the most important parameter is the ratio of the aluminum and oxygen concentrations in the batch. Correct selection of this ratio entails a compromise between the completeness of reduction of the oxides, the content of aluminum and oxygen in the steel (the degree of reduction), and its contamination with aluminum nitride. Cast ingots of Cr–N steel are characterized by the structure of nitrogen-containing pearlite (ferrite–nitride mixture), while ingots of Cr–Mn–N steel are characterized by ferrite–austenite structure, with traces of discontinuous austenite decomposition, accompanied by the precipitation of the nitride Cr2N. Quenching leads to complete austenitization of both types of steel. The agreement of the austenite lattice parameter obtained from the diffraction patterns for quenched Cr–Mn–N steel and the value expected from the concentration dependence for Cr–Mn–N steel indicates that all the alloying elements (including nitrogen) dissolve in austenite as a result of holding at the quenching temperature and are fixed in the solid solution by quenching. Tests of the mechanical properties shows that quenched Cr–Mn–N steel is characterized by both high strength and high plasticity. It may be concluded that reduction of oxides by means of aluminum under nitrogen pressure permits the production of high-nitrogen steel whose mechanical properties match those of corresponding steels produced by electroslag remelting under nitrogen pressure.

Cavitation Erosion Behaviors of a Nickel-Free High-Nitrogen Stainless Steel

The cavitation erosion and corrosion characteristic of a nickel-free high-nitrogen stainless steel (HNSS) in distilled water and 0.5 mol/L HCl solution were investigated by conducting gravimetric and electrochemical measurements, including corrosion potential, polarization curves and electrochemical impedance spectroscopy, and the eroded/corroded surface was observed by scanning electron microscopy. The results revealed that the dominant contribution to cavitation erosion damage was the mechanical degradation process, even though the corrosion rate of HNSS was accelerated in 0.5 mol/L HCl solution. Corrosion and mechanical degradation worked synergistically and promoted crack initiation and propagation under cavitation erosion.

A self-healing stainless steel: Role of nitrogen in eliminating detrimental effect of cold working on pitting corrosion resistance

Nickel-free high nitrogen stainless steels (HNS) with two nitrogen contents were studied to elucidate the role of nitrogen in eliminating detrimental effect of cold working on pitting corrosion resistance. It was found that the detrimental effect was caused by the severe deformation areas with deformation bands and completely eliminated in HNS with 0.92 wt.% nitrogen. Meanwhile, nitrogen was found to be significantly enriched as a form of short range ordered [CrN] in the chromium oxide layer of the passive film. Combined with chemical compositions and semiconducting properties analysis, a self-healing reaction involving the nitrogen doping in passive film was concluded.

Investigate the effects of the substrate surface roughness on the geometry, phase transformation, and hardness of laser-cladded Fe-based metallic glass coating

In this research work, a novel investigation of the substrate surface roughness effects on the geometry, the phase transformation, and the hardness of a single laser-cladded track on nickel-free high nitrogen stainless steel used for biomedical applications. First, two samples were sandblasted using 40- and 100-grit Al2O3 abrasive and two other samples were polished using SiC 150- and 240-grit sandpaper to attain four levels of surface roughness. Second, the FeCrMoCB amorphous powder was deposited on each substrate sample using a laser power 2000 W, 45 mm/s scanning speed, and a spot size of 4 × 4 mm. The geometry of the cladded layers was measured using an optical microscope. Furthermore, X-ray diffraction examination was employed to analyze the structure and phases formed within the coating layer. Finally, the microhardness measurement had been carried out and the average values were recorded. The results showed that the width and height of cladded track are increased with the decrease of the substrate surface roughness due to the superior of cohesion force over the adhesion force between the molten coating material and the substrate. Contrary, the amorphous content percentage is increased with the increase of substrate surface roughness. The hardness measurements showed that polished substrate exhibited higher hardness values (1188 and 1278 HV0.1) than the sandblasted samples (1112 and 1196 HV0.1) which is affected by the amorphous content and the phases found within the coating layer. As a conclusion, the polished substrate (240-grit sandpaper) gave the optimum results in terms of geometry, phase formation and hardness.

Investigation of microbiologically influenced corrosion of high nitrogen nickel-free stainless steel by Pseudomonas aeruginosa

High nitrogen nickel-free stainless steel (nickle-free HNS) has been widely used in recent years because of its strong corrosion resistance. However, little is known on its resistance to microbiologically influenced corrosion (MIC). This study investigated the MIC behavior of nickel-free HNS in the presence of marine aerobe Pseudomonas aeruginosa. A 14-day corrosion test demonstrated that the HNS had a largest pit depth of 16.2μm, over three times deeper than that of the abiotic control coupon (4.7μm). Electrochemical tests and surface morphology examination confirmed that HNS was susceptible to MIC.

Effect of Cold Deformation on Friction Wear Property of 00Cr18Mn15Mo2N0.9 High-nitrogen Nickel-free Stainless Steel

Effect of Cold Deformation on Friction Wear Property of 00Cr18Mn15Mo2N0.9 High-nitrogen Nickel-free Stainless Steel

Effect of Cold Deformation on the Friction–Wear Property of a Biomedical Nickel-Free High-Nitrogen Stainless Steel

The microstructural, mechanical and corrosion properties of different cold-rolled biomedical nickel-free high-nitrogen stainless steels (NFHNSSs) were investigated to study the effect of cold deformation on its dry wear resistance as well as corrosion–wear behaviors in distilled water and Hank’s solution. The results indicated that NFHNSS was characterized by stable austenite and possessed excellent work-hardening capacity; due to increasing cold deformation, the corrosion resistance just decreased very slightly and the dry wear rate decreased initially but subsequently increased, while the corrosion–wear resistance was improved monotonically in both distilled water and Hank’s solution in spite of the presence of corrosive ions. The friction coefficients for different cold-rolled NFHNSSs were very close under the same lubricating condition, but they were the largest in distilled water compared to that in dry wear tests and Hank’s solution.

Osteoinduction and long-term osseointegration promoted by combined effects of nitrogen and manganese elements in high nitrogen nickel-free stainless steel.

High nitrogen nickel-free stainless steel (HNS) has attracted particular attention in recent years, because of its potential application in orthopedic implants. However, the effects of HNS on osteoblast differentiation of bone marrow mesenchymal stem cells and long-term osseointegration are still unclear. In this study, a newly developed HNS with high manganese (Mn) content (Fe-21Cr-16Mn-2Mo-0.93N) was successfully manufactured. The HNS exhibited the improved bio-corrosion resistance and surface hydrophilicity compared to 316L stainless steel (316L SS) due to its high nitrogen (N) content. The hydrophilic surface of HNS could promote initial adhesion and spreading of rat bone marrow mesenchymal stem cells (rBMSCs) via the upregulation of the gene expression of integrin α1 and integrin β1. The high Mn and nickel-free content of HNS facilitated rBMSC proliferation. More importantly, it was revealed that ionic manganese from HNS could enhance the expression levels of osteoblast-related genes (RUNX-2, ALP, OCN and OPN) of rBMSCs, as well as promote ALP activity and OCN protein expression. Moreover, the activation of extracellular signal-related kinases (ERK) 1/2 pathway, via which HNS might induce osteogenic differentiation, was observed in rBMSCs cultured on HNS. Finally, based on HNS implantation in rabbit tibiae for 4, 12 and 26 weeks with 316L SS as a control, Micro-CT evaluation, sequential fluorescent labeling and histological analysis consistently demonstrated that HNS evidently promoted new bone formation and bone-implant contact around implants. Biomechanical tests also confirmed the increased bonding strength at the bone-HNS implant interface in both early and late stages. These results suggest that HNS can induce osteogenic differentiation of rBMSCs and promote rapid and long-term osseointegration of implants, which may be attributed to the combined effects of N and Mn elements.