CrN Phase Research Articles

Evading intermediate temperature embrittlement of FeCoCrNiMn high entropy alloy via N-doping

High entropy alloys (HEAs) exhibit high strength and excellent ductility at both room and low temperatures. The loss of ductility with increasing the tensile temperature above room temperature has been widely observed in single phase face-centered cubic structured HEAs. In this work, a N and Si doped FeCoCrNiMn-(N,Si) HEA with preexisting nano-sized Cr2N particles was fabricated by laser powder bed fusion (LPBF) and subsequent cold-rolling and annealing treatment. Tensile testing was conducted on the alloy at 298 K, 573 K, 773 K, 873 K, and 973 K, respectively. It has been shown that the FeCoCrNiMn-(N,Si) alloy with preexisting Cr2N phase exhibits a steady ductility with increasing the tensile temperature. The intermediate temperature embrittlement is evaded in the FeCoCrNiMn-(N,Si) alloy via N-doping. The widely reported loss of ductility with increasing deformation temperature was avoided in present FeCoCrNiMn-(N,Si) HEA by shifting fast segregation of element Cr from GBs into preexisting Cr2N phase due to the high affinity between N and Cr elements, leading to the increases in the content and size of Cr2N particles after high temperature deformation.

Effect of plasma nitriding on microstructure and wear behavior of electrodeposited FeCoNiCr coating

An (FeCoNiCr)N high-entropy alloy coating with a single FCC phase was fabricated on 304 stainless steel by electrodeposition and plasma nitriding. The results indicated that the FeCoNiCr coating exhibited typical granular morphologies and a nearly equiatomic ratio of four elemental compositions. After nitriding, the coating primarily consisted of a high-entropy solid solution phase and a CrN phase, with the microstructure of the (FeCoNiCr)N coating being significantly refined due to the effect of crystallization. The microhardness of the (FeCoNiCr)N coating was 781.30 ± 20.3 HV0.5, considerably higher than that of the FeCoNiCr coating, which was 496.48 ± 21.82 HV0.5. Additionally, the (FeCoNiCr)N coating demonstrated a low friction coefficient and a wear rate of 0.59 and 6.8 × 10−8 mm3/N mm, respectively. The fine microstructure and high resistance to plastic deformation, attributed to solid solution strengthening and dispersion strengthening, were the primary factors contributing to the excellent wear performance of the (FeCoNiCr)N coating.

Enhancing corrosion fatigue performance of 17-4 PH stainless steel by simultaneous aging and plasma nitriding

This study investigated the effects of simultaneous aging and low-temperature plasma nitriding on the corrosion fatigue performance of 17-4 PH stainless steel. Plasma nitriding was conducted under two temperatures of 400 and 500 °C and, for comparison, some other specimens were subjected to aging treatment at the same temperatures and times. Microstructural characterization by scanning electron microscope (FESEM) and electron backscatter diffraction (EBSD) confirmed similar structures at the core in the nitrided and aged specimens, thereby, the influence of nitrogen at the surface of 17-4 alloy could be carefully investigated. X-ray diffraction and grazing incidence X-ray diffraction (GIXRD) identified expanded martensite as the matrix within the nitrided layer, accompanied by CrN, Fe3N, and Fe4N phases. X-ray photoelectron spectroscopy (XPS) analysis revealed high nitrogen concentration, in regions very close to the surface, after nitriding at 500 °C. The N1s spectra shifted towards lower binding energies, indicating interaction between nitrogen and the matrix atoms, and the formation of nitrides in the nitrided layer. The nitrided thicknesses experienced close values at 400 °C (10 h) and 500 °C (5 h), provided at 400 °C the layer was mostly a supersaturated solid solution but at 500 °C it was composed of iron nitrides and chromium nitride. High hardness values of above 1600 HV0.1 were obtained after optimum plasma nitriding as the result of combined effects of solution strengthening induced by nitrogen atoms and the presence of dispersed nitride phases. EBSD results indicated residual stress within the nitrided layer, which would affect the corrosion fatigue resistance. Experimental findings demonstrated that both aging and plasma nitriding substantially enhanced the corrosion fatigue resistance of 17-4 PH stainless steel in 3.5 wt% NaCl. Moreover, simultaneous aging and plasma nitriding proved superior behavior in corrosion fatigue, primarily due to delayed crack initiation and improved fatigue resistance, without the risk of overaging which is detrimental to mechanical properties.

Fabrication of a new core–shell structured magnetic abrasive particles with good performance

The traditional Fe-based magnetic abrasive powders (MAPs) are prone to degrade by corrosion and oxidation. The extremely low stability to some extent limits the development of magnetic finishing. In this study, a new kind of 410 stainless steel-based spherical MAPs with core–shell structure was synthesized by gas nitriding. The nitride layer shows the dendrite structure containing (Fe, Cr)4N phase and lath-like CrN phase. The Zirconium tube roughness can be reduced from 0.280 to 0.153 μm. The origin of the good finishing performance was investigated through the Vickers hardness and nanoindentation tests.

Study on the surface performance strengthening of AlCrN coated cemented carbide by micro-texture laser preparation process

The combined application of coating and surface texture technology on the material surface can enhance its performance. However, the two procedure and their joint mechanism have not been fully revealed. Therefore, this paper takes the micro-textured coated cemented carbide as the research object, and focuses on the influence of preparation procedure and process parameters on surface characteristics and friction behavior. The results show that compared with the coating textured (XT) sample, the textured coating (XW) sample has more advantages in micro-hardness, microstructure and wear degree. The Rockwell hardness of the XT sample is better. Compared with the single coating sample, the coating micro-hardness of the XW sample is increased by 10 %, the Rockwell hardness is reduced by 2 %, the average grain size is reduced by 7.9 %, and the friction force is reduced by 6.2 %. Additionally, within a certain range, the increase of Al content will increase the sample hardness, reduce friction, and inhibit the Cr content and the growth of CrN phase grains. Complete process parameter optimization based on the ideal solution.

Soret-Effect Induced Phase-Change in a Chromium Nitride Semiconductor Film.

Phase-change materials such as Ge-Sb-Te (GST) exhibiting amorphous and crystalline phases can be used for phase-change random-access memory (PCRAM). GST-based PCRAM has been applied as a storage-class memory; however, its relatively low ON/OFF ratio and the large Joule heating energy required for the RESET process (amorphization) significantly limit the storage density. This study proposes a phase-change nitride, CrN, with a much wider programming window (ON/OFF ratio more than 105) and lower RESET energy (one order of magnitude reduction from GST). High-resolution transmission electron microscopy revealed a phase-change from the low-resistance cubic CrN phase into the highly resistive hexagonal CrN2 phase induced by the Soret-effect. The proposed phase-change nitride could greatly expand the scope of conventional phase-change chalcogenides and offer a strategy for the next-generation of PCRAM, enabling a large ON/OFF ratio (∼105), low switching energy (∼100 pJ), and fast operation (∼30 ns).

Microstructure, mechanical properties, and wettability of CrN and CrSiCN coatings with graded architectures

Protective CrN-based coatings are of interest for applications requiring a combination of corrosion resistance and toughness. Here, the processing-microstructure-properties relationships for metallic Cr, binary CrN, and quaternary CrSiCN coatings are reported. Hexamethyldisilazane (HMDS) was used as a single-source organosilicon precursor for Si and C during plasma-enhanced magnetron sputtering (PEMS). By varying the availability of reactive species during coating growth, graded coating architectures were produced. Scanning and transmission electron microscopy revealed that as Si and C content increased, the coating microstructure evolved from a coarse, columnar growth structure (0 at.% Si), to a nanocolumnar structure (3 at.% Si), and, finally, to a dense, nanoscale structure (6 at.% Si). Coating surface topography was characterized using optical microscopy and atomic force microscopy. While the CrSiCN coating deposited at the highest HMDS flow rate exhibited the lowest nanoscale surface roughness (Rq = 6.74 nm), it also had the greatest area fraction of microscopic surface defects. Evidence of the formation of secondary Cr2N phases within the graded interlayers of the coatings was acquired from selected area electron diffraction analysis. However, the practical adhesion of the coatings, as evaluated by the Rockwell C indentation test, was not adversely affected. Nanoindentation testing revealed that greater incorporation of Si and C into the CrN-based coatings increased coating hardness from 25.4 ± 1.6 GPa to 30.7 ± 1.8 GPa and decreased apparent elastic modulus from 295 ± 14 GPa to 284 ± 12 GPa. Contact angle goniometry was conducted to determine the wettability of the coatings. It was found that sessile water contact angles decreased from 86.5° ± 1.6° to 77.3° ± 2.1° as coating Si and C content increased.

Effect of Tempering Temperature on Microstructure and Intergranular Corrosion Property of 2205 Duplex Stainless Steel

The effect of tempering temperature on the microstructure and intergranular corrosion property of 2205 duplex stainless steel (DSS2205) was determined using a boiling acid intergranular corrosion test (boiling 65% nitric acid and 50% sulfuric acid–ferric sulfate), an optical microscope, a transmission electron microscope, and a double-loop electrochemical potentiokinetic reactivation (DL-EPR) test. The results show that the ferrite content of the DSS2205 is about 50% in a specimen close to a solid solution state (1050 °C for 1 h, then water-quenched) when tempered at 675 °C–725 °C for 1 h. As the tempering temperature rises to 750 °C–800 °C for 1 h, the ferrite content drops gradually from 49% to 35%. M23C6, FeCr (σ phase), and Cr2N phases are precipitated when the specimen is tempered at 675°C–800 °C for 1 h. When the tempering temperature rises to 750 °C–800 °C for 1 h, the content and size of σ phase increase significantly. In the boiling acid intergranular corrosion test, when the specimen is tempered at 675 °C–725 °C for 1 h, the corrosion rate is higher than when it is tempered at 750 °C–800 °C for 1 h. In the DL-EPR test, when the specimen is tempered at 675 °C–800 °C for 1 h, the intergranular corrosion sensitivity rises gradually. External polarization is added during the DL-EPR test, and the test principle is different from that of the boiling acid intergranular corrosion test, resulting in a different sensitivity to intergranular corrosion compared to boiling acid intergranular corrosion.

Microstructural transformation and failure mechanism of CrN/CrTiSiN coatings experienced annealing post-treatment

There are great efforts for enhancing the characteristics of PVD multilayered coatings and one solution could be heat treating the coated part. The current research analyzed the effect of annealing temperatures on the microstructural transformation and failure mechanism of CrN/CrTiSiN multilayered coatings. The coatings were annealed in air at temperatures ranging from 500 °C to 1000 °C for 1 h. The characterization methods included XRD, XPS, FESEM, EDS, and Rockwell-C adhesion tests. The findings indicated that the as-deposited coating exhibited a consistent structure of the CrN phase. During the process of annealing from 500 to 700 °C, the CrN phase transforms into the Cr2N phase. At 800 °C, the structure is fully composed of Cr2N. At 900 °C, the elevated annealing temperature causes the Cr2N phase to change into the Cr2O3 phase. The volume fraction of the Cr2O3 phase increases until the temperature reaches 1000 °C. The results showed that the transition of Cr2N → Cr2O3 within the coating's thickness would lead to peeling off the coating due to an increase in the lattice volume. The EDS mapping shows that raising the annealing temperature for a constant time will result in more oxygen infiltration into the coating's thickness.

Enhancing thermoelectric performance of CrN ceramics by optimizing sintering temperature

Chromium nitride (CrN) ceramics were sintered at various temperatures by plasma activated sintering, and their thermoelectric properties were explored. The formation of Cr2N phase can be suppressed by venting N2 gas into the chamber before sintering and increasing the sintering temperature to accelerate the densification process. Sintering temperature significantly impacted the thermoelectric properties. Higher sintering temperature led to an increase in the N content, reducing the electrical and thermal conductivity, and increasing the Seebeck coefficient. The single-phased CrN ceramic sintered at 1573 K exhibited excellent thermoelectric performance with a maximum power factor of 1002 μW·m−1·K−2, a thermal conductivity of 4.78 W·m−1·K−1, and a zT value of 0.20 at 973 K. Furthermore, this CrN ceramic also exhibited a high relative density of 97% and a hardness of ∼11.9 GPa. Enhanced high-temperature thermoelectric properties and excellent mechanical properties make CrN ceramics suitable for thermoelectric applications in extreme environments.

Exploring microstructural evolution, nitrogen depth profile, and dry wear performance in 31CrMoV9 steel through combined severe shot peening and plasma nitriding

The present study investigates the influence of severe shot peening (SSP) on the plasma nitriding behavior and sliding wear performance of 31CrMoV9 steel. Initially, the steel was austenitized at 880 °C, followed by oil quenching, and tempering at 520 °C for one hour. These samples were shot peened using high-carbon steel shots, resulting in an enhancement in surface hardness up to 447 HV, gradually converging to the initial martensitic hardness after 140 µm depth. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) scrutinized the initial and surface treated martensitic samples. Afterward, the plasma nitriding treatments were carried out at temperatures of 400 °C, 450 °C, and 500 °C for 8 hours in a 30% N2 + 70% H2 atmosphere and 300 Pa pressure. Microhardness testing, SEM, XRD, and glow-discharge optical emission spectroscopy (GDOES) evaluated both plasma nitrided (PN) and severe shot peened/plasma nitrided (SSP-PN) samples. Cross-sectional SEM observations revealed compound layer thicknesses of approximately 2.8 µm, 5.0 µm, and 6.3 µm for PN samples at 400 °C, 450 °C, and 500 °C, respectively. SSP-PN samples exhibited a substantial increase — roughly 71%, 44%, and 33% increase, respectively, compared to PN samples. GDOES analysis supported this trend and indicated enhanced nitrogen diffusion depth, particularly evident in SSP-PN samples at consistent temperatures. The XRD results showed the stability of Fe4N, Fe2–3N, and CrN phases at all three nitriding temperatures. Furthermore, the intensity of these phases increases with temperature and is augmented by the application of the SSP. Microhardness measurements indicated hardness escalation: from 775 HV to 980 HV at 400 °C, 932 HV to 1096 HV at 450 °C, and 1011 HV to 1205 HV at 500 °C due to SSP. Finally, the wear performance was investigated between the non-nitrided, SSP, PN, SSP-PN, samples. Initially, SSP led to decreased wear performance up to 500 m, followed by improved behavior up to 1500 m. At 400 °C, the SSP-PN sample exhibited a 12% lower wear rate than PN. At 450 °C and 1500 m, the SSP-PN sample displayed a 24% reduction, while at 500 °C, it showed a 27% reduction compared to PN. SEM observations indicated abrasion as the primary wear mechanism across all samples. The overall results indicated a significant similarity in the nitrogen depth profile, hardness depth, and wear performance between the SSP-PN sample at 450 °C and the PN sample at 500 °C. The fact suggested a potential reduction of approximately 50 °C in the typical plasma nitriding temperature for 31CrMoV9 steel as a result of the SSP process.

Study of Precipitated Secondary Phase at 700 °C on the Electrochemical Properties of Super Duplex Stainless Steel AISI2507: Advanced High-Temperature Safety of a Lithium-Ion Battery Case.

Super duplex stainless steel (SDSS) is a suitable structural material for various engineering applications due to its outstanding strength and corrosion resistance. In particular, its high-temperature strength can enhance the safety of electronic products and cars. SDSS AISI2507, known for its excellent strength and high corrosion resistance, was analyzed for its microstructure and electrochemical behavior at the ignition temperature of Li-ion batteries, 700 °C. At 700 °C, AISI2507 exhibited secondary phase precipitation values of 1% and 8% after 5 and 10 h, respectively. Secondary phase precipitation was initiated by the expansion of austenite, forming sigma, chi, and CrN phases. The electrochemical behavior varied with the fraction of secondary phases. Secondary phase precipitation reduced the potential (From -0.25 V to -0.31 V) and increased the current density (From 8 × 10-6 A/cm2 to 3 × 10-6 A/cm2) owing to galvanic corrosion by sigma and chi. As the fraction of secondary phases increased (From 0.0% to 8.1%), the open circuit potential decreased (From -0.25 V to -0.32 V). Secondary phase precipitation is a crucial factor in reducing the corrosion resistance of SDSS AISI2507 and occurs after 1 h of exposure at 700 °C.

Characterization of Cr/CrN nano multilayers obtained through reactive sputtering with different degrees of unbalance in the magnetron

Nanoscale hard coatings of bilayers of Cr/CrN were obtained and characterized through unbalanced magnetron sputtering (UBMS) in an atmosphere of Ar and Ar + N2 on silicon and hardened and tempered H13 steel, with a degree of unbalanced K0 between 0.87 and 1.37. The deposition parameters were as follows: a power of 160 watts, Ar and N2 flow rates of 9 and 3 sccm, and a substrate target distance of 5 cm. A Gen coa VT 100 magnetron with varying degrees of unbalance, obtained by displacing its central magnet, was used. The electrochemical behavior of these coatings was characterized using the technique of potentiodynamic anodic polarization. The coatings' microstructure and hardness were analyzed via X-ray diffraction (XRD) and nanoindentation tests; Cr, CrN, and Cr2N phases were obtained, with a hardness that increases with the degree of unbalance between 18.90 and 24.97 GPa.

Comparative Plasma Nitrocarburizing of AISI 316L and AISI 304 Steels Using a Solid Carbon Active Screen: Differences in the Developing Microstructures

This paper features a direct comparison of the response of AISI 316L and AISI 304 austenitic stainless steels to active screen plasma nitrocarburizing applied for a wide range of treatment temperatures from 380 °C to 480 °C (653 K to 753 K). Thereby, an active screen made of solid carbon was used without applying bias plasma to the treated steel samples. Since it is believed that the result of treatment strongly depends on the concentration of in-situ generated hydrogen cyanide, the conditions of the treatments were adapted to keep this concentration constant. Under such treatment conditions, it was shown that AISI 316L has a lower tendency to form CrN than AISI 304 at comparable treatment temperatures, where the threshold temperature was found below 480 °C (753 K) for the former and below 440 °C (713 K) for the latter. In addition, the decomposition of expanded austenite generated on the treated AISI 316L at high temperatures leads to CrN and (mainly) Cr-depleted austenite phase, which is possibly accompanied by minor amounts of α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha$$\\end{document}-ferrite. Instead, for the treated AISI 304, decomposition leads to CrN and transformed α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha$$\\end{document}-ferrite phase. The modified layer thicknesses achieved after a given treatment duration and the kinetics of the layer growth showed a characteristic temperature dependence for each steel, which is discussed in accordance with the results of microstructure analysis.

Enhancing wear resistance: In-situ ceramic phase precipitation for strengthening and toughening FeCoNiCrNx high-entropy alloy films

FeCoNiCr high-entropy alloys have attracted widespread attention because of their excellent toughness; however, their insufficient hardness limits their application in wear-resistant films. The introduction of non-metallic elements is an effective method for strengthening high entropy alloys films. In this study, high-entropy alloy films of FeCoNiCrNx with varying nitrogen content were fabricated using reactive magnetron sputtering. The influence of nitrogen content on the structure, mechanical properties, and tribological behavior of these high-entropy alloy films was studied. With an increase in nitrogen content, the FeCoNiCrNx film undergoes amorphization and simultaneous precipitation of Cr2N phases. At lower nitrogen flow rates (0–4 sccm), the film exhibits lower hardness (8.51–10.97 GPa) and poor wear resistance. At moderate nitrogen flow rates (8 sccm), the film exhibits enhanced hardness (12.8 GPa) and toughness, leading to favorable wear resistance (4.04 × 10−6 mm3 N−1 m−1). A further increase in the nitrogen flow rates (12–16 sccm), while raising hardness (13.08–15.17 GPa), leads to a slight reduction in toughness and consequently, a mild decrease in wear resistance (4.37–5.09 × 10−6 mm3 N−1 m−1). A biphase structure design combining FeCoNiCr high entropy alloy and ceramic (Cr2N) improved the strength and toughness of FeCoNiCrNx and significantly enhanced its wear resistance, thus enhancing its application potential.

Enhancing mechanical and tribological performance of CrN/CrTiSiN coating through annealing treatment

The primary objective of the present investigation is to examine the effects of air annealing on the mechanical, tribological, and structural properties of multilayer CrN/CrTiSiN coatings. The deposition of CrN/CrTiSiN multilayer coatings on a Ti6Al4V substrate was carried out using CAE-PVD technique. Subsequently, the as-deposited coatings were subjected to annealing in ambient air environment at a temperature of 600 °C for 1 h. The characterizaion purposes were achieved by XPS, XRD, FESEM, nanoindentation, Rockwell-C adhesion tests, and pin-on-disk wear tests. The results suggest that the annealing process led to the development of new Cr2N, Cr2O3, and SiO2 phases. The coating hardness increased from 21.5 GPa to 25.3 GPa by annealing process. The findings from the pin-on-disc experiment indicate that the wear resistance of the annealed coating exhibited superior performance when compared to both the as-deposited coating and the substrate. The improvment could be attributed to the annihilation of the residual stress and the formation of new phases on the surface.

Investigation on AISI 253 Stainless Steel by Gas Nitriding Process for Sustainable Applications

Austenitic stainless steel is highly valued in many industries due to its unique properties, which make it appropriate for various sustainable applications like wind turbine blades, solar panel components, biomass converter equipments. AISI 253 stainless steel were chosen for this research and gas nitrided were underwent at a low temperature of about 550°C. The samples were nitride for 8 hours of nitriding, the sample was found to move from austenitic to expanded austenite phase. Extending the nitriding time to 16 hours resulted in the formation of ferrites and an increasing concentration of nitrogen in succeeding layers. The specimens were carried out with nitriding for 24 hours. Cr-N phase were formed was This new phase contributes to increase in surface hardness. Wear loss and volume loss were analyzed from the wear test. In this work , there was considerable improvement in the wear resistance after 24hours of nitriding. The samples nitrides for 24 hrs also had high hardness of 1080Hv and had negligible wear, volumetric wear loss of the specimens. The microstructure and surface morphology analysis of the nitrided samples was carried out using scanning electron microscopy which helped in establishing the microstructural behaviour of the AISI 253 stainless steel.

Identification of Expanded Austenite in Nitrogen-Implanted Ferritic Steel through In Situ Synchrotron X-ray Diffraction Analyses

The existence and formation of expanded austenite in ferritic stainless steels remains a subject of debate. This research article aims to provide comprehensive insights into the formation and decomposition of expanded austenite through in situ structure analyses during thermal treatments of ferritic steels. To achieve this objective, we employed the Plasma Immersion Ion Implantation (PIII) technique for nitriding in conjunction with in situ synchrotron X-ray diffraction (ISS-XRD) for microstructural analyses during the thermal treatment of the samples. The PIII was carried out at a low temperature (300–400 °C) to promote the formation of metastable phases. The ISS-XRD analyses were carried out at 450 °C, which is in the working temperature range of the ferritic steel UNS S44400, which has applications, for instance, in the coating of petroleum distillation towers. Nitrogen-expanded ferrite (αN) and nitrogen-expanded austenite (γN) metastable phases were formed by nitriding in the modified layers. The production of the αN or γN phase in a ferritic matrix during nitriding has a direct relationship with the nitrogen concentration attained on the treated surfaces, which depends on the ion fluence imposed during the PIII treatment. During the thermal evolution of crystallographic phase analyses by ISS-XRD, after nitriding, structure evolution occurs mainly by nitrogen diffusion. In the nitrided samples prepared under the highest ion fluences—longer treatment times and frequencies (PIII 300 °C 6 h and PIII 400 °C 3 h) containing a significant amount of γN—a transition from the γN phase to the α and CrN phases and the formation of oxides occurred.

Effect of Multiple Reverse Transformation Treatments on Grain Refinement and Mechanical Properties of Biomedical Co-Cr-Mo-N Alloys Fabricated by Electron Beam Melting.

We investigated the improvement of mechanical properties of biograde Co-28Cr-6Mo-0.11N alloy prepared by electron beam melting through grain refinement via multiple reverse transformations. While the effects of single and double reverse transformation treatments on the microstructure have been investigated in previous studies, we investigated the effects of multiple reverse transformation heat treatments. The particle size was refined to 1/4, and the yield strength, tensile silence strength, and elongation were enhanced to 655 MPa, 1234 MPa, and 45%, respectively, satisfying ASTM F75 standards. Moreover, a mixed phase of ε and γ was observed to provide higher yield strength than a single γ structure. The dominant behavior in the γ → ε phase transformation at 1073 K was obvious. Grain growth was suppressed by the grain-boundary pinning effect of the Cr2N phase during reverse transformation to the γ phase. Because no fracture was caused by precipitates such as σ, η, and Cr2N phases, the influence of the precipitates on the tensile properties was small.

Effect of yttrium addition on precipitated phase, corrosion resistance, and mechanical behavior of 6Mo superaustenitic stainless steel

Optimizing alloy composition is an effective method to regulate the microstructure and improve the properties of superaustenitic stainless steel (SASS). In this research, 6Mo SASS containing 16 ppm and 83 ppm yttrium (Y) was prepared, and the effects of Y microalloying on secondary phase precipitation and materials performance were investigated. It was found that higher Y content could better inhibit the sigma(σ) and Cr2N phase precipitation along the grain boundary, leading to the improvement of the intergranular corrosion (IGC) resistance and mechanical properties of aged steels.