Pure Ar Gas Research Articles

The improvement of dry sliding tribological properties by designing nano-primary cementite in bainitic/martensitic matrix microstructure in hypereutectoid PM components

The production of nano-sized primary cementite in bainite/martensite matrix (NCBM) microstructure was designed to improve the dry sliding wear properties of high carbon PM parts. A different heat treatment cycle was carried out for the production of novel the NCBM microstructure. High purity iron powder 1.5 wt%. natural graphite powder was added and it was compacted in the form of a dry sliding wear test specimen in a mold and sintered at 1200 °C in a pure Ar gas atmosphere. The novel NCBM microstructure in the PM material was produced by quenching at 950 °C, then annealing at 600 °C for 12 min, then quickly cooling from 730 °C to 250 °C in a salt bath and keeping it isothermal for 100 s. The friction coefficient of materials with NCBM microstructure was less than other samples. It was found that while the wear coefficient were higher in the tempered martensitic microstructure sample having higher hardness, they were less than in the sample having bainitic/martensitic microstructure with similar hardness.

Effect of Ar pressure on phase transition characteristics and charge transport mechanism in VO2 films grown by RF sputtering of V2O5

In this study, we report the growth and characterization of VO2 films deposited on YSZ (001) substrate employing RF magnetron sputtering of vanadium pentoxide (V2O5) target in pure Ar gas ambient. The VO2 film growth has been carried out at ∼700 °C for ∼15 min at ∼100 W RF power with a flow rate of ∼20 sccm at Ar gas deposition pressure of ∼3, ∼6, ∼20, and ∼40 mTorr. x-ray diffractometry and Raman spectroscopy show that the nearly pure VO2 phase achieved at lower Ar pressure, e.g., ∼3 and ∼6 mTorr transform into a multiphase V-O system at ∼20 and ∼40 mTorr. This pattern is also supported by the electrical transport measurements through the occurrence of hysteretic IMT in films grown at ∼3 and ∼6 mTorr and the absence of this signature in these films deposited at ∼20 and ∼40 mtorr Ar pressure. The most pronounced with the strongest hysteresis is seen in the Y6 film, and therefore, the optimum growth pressure in the present study is ∼6 mTorr. The suppression of IMT in Y20 and Y40 is attributed to the appearance of other V-O phases, which smear out the phase transition. The activation energy of the insulating phase is estimated from the Arrhenius fit to the ρ-T data is found to be ∼0.223 eV at ∼3 mTorr Ar pressure which increases to ∼0.311 eV for ∼6 mTorr film in the cooling cycle. The low temperature (120K≤T≤300K) transport conduction in all VO2 films is governed by Efros-Shklovskii’s variable range hopping (ES-VRH) mechanism with a systematic relation between growth conditions and phase transition characteristics. Thus, Argon gas pressure plays a critical role in growth and brings out the feasibility of VO2 films growth by RF sputtering of oxide V2O5 target under Argon ambient only.

Additively manufactured high entropy alloy with high wear resistance for biomedical implant

Titanium and its alloys play a vital role as implant materials in orthopedic and dental surgery. However, its poor wear resistance limits its application in the medical field. High entropy alloy (HEA) has high wear resistance due to the combined action of high entropy, lattice distortion, and cocktail effects. In this work, TiFeCrCoNi HEA is prepared by Laser powder bed fusion (LPBF) under the protection of high pure Ar gas. The results show the TiFeCrCoNi HEA has mainly FCC phase and a small amount of Hexagonal and Laves phases. Its microhardness is up to 776.3 ± 21.4 H V and is 2.8 times that of pure Ti. Meanwhile, the HEA has a low friction coefficient of 0.1–0.15, which is attributed to high hardness precipitates and grain refinement. The main wear mechanism of the HEA is oxidation wear, adhesive wear, and abrasive wear. In addition, the TiFeCrCoNi HEA also demonstrates good biocompatibility.

Effect of shielding gas on surface formation during laser welding of Al-Si coated press-hardened steels

The Al-Si coating was negative to the laser welding of press-hardened steel (PHS). This study carried out the comparative analysis of the shielding gas (Pure Ar and CO2 shielding gas) on the surface formation of welded seam. The results showed that the intermittent umbrella-shaped Fe-Al intermetallic compounds (IMCs) on both sides of the weld were presented for the Ar shielding gas, but it was disappeared for CO2 shielding gas. The adjacent Al-Si coating on the humps of the molten pool was melted by the heat conduction of the liquid metal, and flowed into the molten pool at the gap of two humps. The reaction between Fe and Al occurred to form Fe-Al IMCs as umbrella-shaped. The CO2 shielding gas provided a reaction opportunity with liquid Al to form the floated film on the surface of molten pool due to low Gibbs free energy, which presented particles oxides on the weld surface after solidification.

Fabrication of Graphene Sheets Using an Atmospheric Pressure Thermal Plasma Jet System

The mass production of cost-effective, large area, defect-free and high crystal quality graphene sheets with a high yield is a challenging task. In order to investigate the mechanisms involved, we report on the synthesis of graphene sheets by a homemade atmospheric pressure thermal plasma jet system, which is a single-step and less time-consuming technique. The samples were prepared by using pure Ar gas and a mixture of Ar and N2. The microstructure of the synthesized graphene sheets was characterized with the help of Raman spectroscopy, field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared (FTIR) spectroscopy. The appearance of G and 2D peaks in the Raman spectrum confirmed the formation of graphene. Moreover, we observed that the addition of nitrogen increased the production of the graphene sheets but compromised the quality of those graphene sheets by increasing their structural defects. The morphology of the synthesized samples studied via FE-SEM images showed that the sheets were composed of multilayers. FTIR spectra show the presence of C=C and a hydroxyl group directly bonded to the aromatic hydrocarbon.

Jet shape analysis and removal function optimization of atmospheric plasma processing applied in optical fabrication

When inductively coupled plasma (ICP) is used as a machining tool, its chemical etching-based processing method has the advantage of no contact stress between the tool and the material, thus without any mechanical damage. In recent years, this issue has been widely concerned in optical fabrication. However, there are many differences between low power ICP jet and conventional ICP jet, one of which is that the former does not easily form a rotation-symmetric removal function due to its obvious pinch effect. In this research, the electromagnetism principle of the plasma pinch effect was analyzed firstly, and the jet shape under the pinch effect was classified. Then, experiment was carried out to investigate the plasma jet shape under the pure Ar and mixed gas of CF4-Ar, and the influence law of the reaction gas on the jet propagation shape was analyzed. Finally, the rotational symmetry of the removal function of plasma jet processing was optimized, and the nozzle design criteria were proposed based on pinch effect.

Modulation of spin Seebeck effect by hydrogenation

We demonstrate the modulation of spin Seebeck effect (SSE) by hydrogenation in Pd/YIG bilayers. In the presence of 3% hydrogen gas, SSE voltage decreases by more than 50% from the magnitude observed in pure Ar gas. The modulation of the SSE voltage is reversible, but the recovery of the SSE voltage to the prehydrogenation value takes a few days because of a long time constant of hydrogen desorption. We also demonstrate that the spin Hall magnetoresistance of the identical sample reduces significantly with hydrogen exposure, supporting that the observed modulation of spin current signals originates from hydrogenation of Pd/YIG.

Effect of Surface Microstructure on the Hydrogen Permeation Behavior of Plasma-Nitrided AISI 4135 Steel

Hydrogen embrittlement is a serious problem for high strength steels. The reduction of hydrogen uptake by the formation of surface layers with low hydrogen diffusivity is thought to be effective in preventing hydrogen embrittlement. We reported that the plasma-nitrided surface layer composed of ε-Fe2-3N and γ’-Fe4N phases strongly inhibited hydrogen diffusion into the pure iron matrix.1) In this study, we controlled the microstructure of surface nitrided layers of an AISI 4135 steel by plasma nitriding, and investigated the hydrogen permeation behavior.AISI 4135 steel sheets of 1 mm in thickness were used as the specimens. Prior to plasma nitriding, the specimen surfaces were polished using a diamond past down to 1 μm. The plasma nitriding treatments were conducted in nitrogen-hydrogen atmospheres at 600 Pa for 3.6 ks. The temperature of the specimen surface was kept at 450 °C. Two types of nitrogen compound layers were formed on the specimen surface by changing the mixing ratio of nitrogen and hydrogen gases. One was composed of ε-Fe2-3N and γ’-Fe4N phases (specimen A), and the other was done of only γ’-Fe4N phase (specimen B). The compound layers of specimen A and B were 10 μm and 1 μm in thickness, respectively. In addition, the thicknesses of the nitrogen solid solution layers of specimen A and B were estimated to be ca. 270 μm and 210 μm, respectively.To investigate the effect of the surface microstructure on the hydrogen permeation through the specimens, the hydrogen permeation test using a conventional Devanathan-Stachurski cell was carried out. The nitrided surface was arranged in the hydrogen detection side. A Pd thin film was deposited on the specimen surfaces in the hydrogen detection side. The hydrogen detection side was polarized at 0.18 V vs. SHE in 0.1 M NaOH fully deaerated by pure Ar gas. The hydrogen entry side was polarized at −0.4 V vs. SHE in 0.1 M H2SO4. The hydrogen permeation test of specimen A reveals that the rise transient of the hydrogen permeation current was delayed and the steady state permeation current was significantly reduced. On the other hand, the hydrogen permeation behavior of specimen B was almost similar to that of the as-polished specimen. These results indicate that the nitrogen compound layer composed of ε-Fe2-3N and γ’-Fe4N phases inhibits the hydrogen permeation. Particularly, the existence of ε-Fe2-3N phase with the hcp structure is thought to be effective in preventing the hydrogen permeation.1) Y. Sugawara, I. Muto, and N. Hara, ECS Trans, 75(29), 43 (2017).

Residual oxygen driven defect mediated room temperature magnetism in dilute nitrogen incorporated amorphous Al-N-O alloy thin film

In the present work, the effect of residual oxygen during reactive sputtering of Al target in a dilute nitrogen environment has been investigated. We have deposited a thin film by reactive sputtering of high purity Al target (99.999%) using a mixture of ultra-high pure Ar & N2 gas in a percentage ratio of 95% and 5%, respectively. The characterization of as-deposited film using Grazing Incidence X-ray Diffraction (GIXRD), X-ray Photoelectron Spectroscopy (XPS), and Energy-Dispersive X-ray (EDX) spectroscopy reveals that in dilute nitrogen environment Al preferred to react with residual oxygen to form amorphous Al2O3 (a-Al2O3) along with aluminum vacancies (AlV). The dilute nitrogen incorporated in the film occupies the AlV sites in Al2O3 and bonded with nearby oxygen to form Al(NOy)x phase. The bulk of the film mainly consists of Al(NOy)x phase, which decreases as we move towards the film surface. At close to the film surface the oxygen vacancies are significantly present. Magnetic and electrical transport properties measurement of the film shows room temperature (RT) magnetism along with n-type semiconducting behaviour. The origin of RT magnetism and observed transport properties have been investigated using a first-principle calculation based on density functional theory (DFT). The residual oxygen driven defects present in the film are found to play a critical role and discussed in detail. The current study is significant in the sense that it provides a new insight to explore the potentials of Al-N-O alloy-based materials as an n-type magnetic semiconductor at room temperature by manipulating defects and optimizing nitrogen concentration.

Influence of Shielding Gas on Microstructure and Properties of GMAW DSS2205 Welded Joints

In the present study, the microstructures and properties of DSS 2205 solid wire MIG welded samples prepared in different shielding gases (pure Ar gas, 98%Ar + 2%O2 and 98%Ar + 2%N2) were investigated for improving the weldability of DSS 2205 welded joint. The work was conducted by mechanical property tests (hardness and tensile test) and corrosion resistance property tests (immersion and electrochemical tests). The results show that adding 2%O2 into pure Ar gas as the shielding gas decreases crystal defects (faults) and improves the mechanical properties and corrosion resistance of the welded joints. Phase equilibrium and microstructural homogeneity in welded seam (WS) and heat-affected zone (HAZ) can be adjusted and the strength and corrosion resistance of welded joints increased obviously by adding 2%N2 to pure Ar gas as the shielding gas. Compared with DSS 2205 solid wire MIG welding in 98%Ar + 2%O2 mixed atmosphere, the strength and corrosion resistance of welded joints are improved more obviously in 98%Ar + 2%N2 mixed atmosphere.

Experimental study on the conductance of pure and binary gas mixtures

A binary gas mixture conductance measurement apparatus with an independent gas distribution system was established, the constant volume method to measure the conductance of the mixed gas was used. Also, the conductance of pure gas Ar, He, N2 and binary gas mixtures Ar–He, N2–He, Ar–N2 through a short tube under different gas distribution chamber pressures and different molar fractions were measured. Meanwhile, the equivalent single gas method was used to calculate the conductance of binary gas mixtures. To verify the accuracy of this method, the relative error between the calculated and the measurement was carried out. The result shows that the equivalent single gas method is suitable for a small Knudsen number (1/Kn≥10), the molar fraction of lighter species is low and a small difference in the molecular mass of the components in the mixed gas. The uncertainty of conductance measurement is better than 3.1%.

Performance and aging studies for the ALICE muon RPCs

The ALICE muon trigger (MTR) system consists of 72 Resistive Plate Chamber (RPC) detectors arranged in two stations, each composed of two planes with 18 RPCs per plane. The detectors are operated in maxi-avalanche mode using a mixture of 89.7% C2H2F4, 10% i-C4H10 and 0.3% SF6. A number of detector performance indicators, such as efficiency and dark current, have been monitored over time throughout the LHC Run2 (2015–18). While the efficiency showed very good stability, a steady increase in the absorbed dark current was observed.Since the end of 2018, the LHC has entered a phase of long shutdown, during which the ALICE experiment will be upgraded to cope with the next phase of data taking, expected in 2021. The MTR is undergoing a major upgrade of the front-end and readout electronics, and will change its functionalities, becoming a Muon Identifier [1]. Only the replacement of the most irradiated RPCs is planned during the upgrade. It is therefore important to perform dedicated studies to gain further insights into the status of the detector. In particular, two RPCs were flushed with pure Ar gas for a prolonged period of time and a plasma was created by fully ionizing the gas. The output gas was analyzed using a Gas Chromatograph combined with a Mass Spectrometer and the possible presence of fluorinated compounds originating from the interaction of the plasma with the detector inner surfaces has been assessed using an Ion-Selective Electrode station.This contribution will include a detailed review of the ALICE muon RPC performance at the LHC;the procedure and results of the argon plasma test, described above, are also discussed.

Laser ablation molecular isotopic spectrometry for analysis of OD/OH isotopologues in plasma

Laser ablation molecular isotopic spectrometry (LAMIS) was recently reported for isotope analysis of samples and for molecules formation mechanism investigation by analyzing the isotopologues in laser induced plasma. LAMIS was utilized to quantify the OD and OH molecules in fs-laser ablated plasma from moist water samples carried by pure Ar gas at ambient environment. A theoretical spectral fitting model for OD and OH molecules was developed and was used to extract the isotopic ratio OD/OH by fitting of experimental spectra. Time-resolved spectra were measured and the influences of spectrum intensity and signal to noise ratio (SNR) on isotopic quantitative analysis performance were evaluated. The relative concentration of OD and OH molecules in laser induced plasma from a set of water samples with D2O concentrations in the range of 0% to 99.8% are quantified, and a very good linear relationship between D concentration and D2O concentration was obtained. The linear curve exhibited R2 exceeding 0.9997 and a slope of 1.006. In addition, no standard sample is necessary for quantitative analysis, demonstrating the advantages of spectral fitting LAMIS.

Limitations of the Schlieren technique for shielding gas flow visualization in arc welding processes

Gas protection is very important in arc welding processes and several factors influence its effectiveness. This paper provides a discussion of the applicability of the Schlieren technique to arc welding processes. Tests were performed with different types of shielding gas and with GMAW and GTAW torches, in order to highlight differences associated with the various conditions. The results obtained in conjunction with a review of results reported in the literature allowed an evaluation of the limitations associated with the use of the Schlieren technique in the arc welding processes. The most important limitation is that the visualization is inherently difficult when using pure Ar gas, meaning that in most situations it is not possible to adequately visualize the flow interface with atmospheric air, which is the main region of interest in this type of analysis. However, visualization is possible in regions where pure Ar is heated, or when mixtures with other gases are used. In addition, the results obtained with different sources of light were compared and the test was performed by filming the arc welding or with the gas flowing through the torch without the arc. The differences observed in the results obtained are discussed herein.

Mechanical Properties and Corrosion Resistance of Borosintered Distaloy Steels

Distaloy SA is a sponge iron powder (nominal composition: Fe-1.75Ni-1.5Cu-0.5Mo) widely used in the production of powder metallurgy (P/M) parts in the automotive industry. In this study, Distaloy SA powders were sintered in two different atmospheres, one consisting of pure Ar gas (traditional sintering) and the other consisting of a mixture of 90 wt.% B4C and 10 wt.% NaBF4 powders (borosintering). To investigate the effects of the different sintering atmospheres, the P/M samples were characterized using density measurements, surface roughness tests, scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction, microhardness measurements, nanoindentation experiments, wear tests and corrosion tests. On the surface of the borosintered samples, a 160-325 µm thick double-phase FeB + Fe2B boride layer was formed. The hardness (1405-1688 HV) and elastic modulus (122.21-162.42 GPa) of the surface were significantly improved with the borosintering treatment compared to conventional sintering (215-250 HV, 63.28-94.86 GPa). Borosintering also provided low friction coefficient values and an increased wear resistance compared to conventional sintering. A significant increase in corrosion resistance was also observed with the borosintering treatment in three different solutions. The corrosion rates of both sintered and borosintered samples were ranked as NaCl < HCl < H2SO4. The borosintered samples displayed superior corrosion resistance compared to the sintered samples, especially in the acid solutions. The results of this study show that significant cost savings can be achieved by combining the boriding and sintering treatments in a single borosintering process.

High Harmonic Generation in Ar and N2 Gas Mixture Using Ultrashort High Power Laser System

High harmonic generation (HHG) has been accepted as a tool for tabletop based generation of light source in the XUV and soft x ray region. HHG can produce coherent optical pulses having pulse duration in the femtosecond or even attosecond time region. In this paper, generation of high harmonics are produced by using high power laser system having optical pulses at 6mj pulse energy with pulse duration of 50fs at 10Hz repetition rate. High harmonics in pure Ar, N2 and mixture of the Ar-N2 are used as a generation medium to produce high harmonics. The harmonic signal is increased or decreased depending on the experimental condition. Harmonic yield produced in Ar is stronger than harmonic yield produced in N2 gas. Generation of high order harmonics are observed up to 35H (~54eV corresponding photon energy), and harmonic order from N2 gas is 33H. The mixture of two gas species cause to enhancement of 35H order, which is weakly observed in pure N2 gas. The mechanism of high harmonic generation is explained that strong harmonic signal generated in pure Ar gas helps increase the ionization rate of N2 gas. Thus, the harmonic signal in Ar-N2 is boosted compared the harmonic signal produced in pure N2. The enhancement factor of harmonic yield is from ~2 to 5 for per harmonic order.

High-dielectric-constant silicon nitride thin films fabricated by radio frequency sputtering in Ar and Ar/N2 gas mixture

In this work, dielectric behaviour, photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS) analyses of silicon nitride (Si-nitride) dielectric films sputtered with radio frequency and Si3N4 sputtering target under pure Ar and Ar/N2 (50/50) mixed gas flow sputtering ambient. The dielectric constant of sputtered Si-nitride dielectric film with Ar/N2 (50/50) mixed gas flow sputtering ambient can be up to 17, which is higher than that with pure Ar gas flow sputtering ambient. In addition, the dielectric constant of 17 is higher than all the reported dielectric constants of sputtered Si-nitride dielectric films and matches the dielectric constant of the Si-nitride dielectric films fabricated by the chemical vapour deposition process. XPS analysis shows that N-deficient SiNx is the major phase (approximately 54.7%) in the Si-nitride dielectric film sputtered with Ar/N2 mixed gas flow. The N species (neutral and ionized N) generated in the sputtering ambient enable the formation of the N-deficient SiNx phase in the Si-nitride dielectric film. N vacancy defects with negative charges in the Si-nitride film prepared with Ar/N2 (50/50) mixed gas flow are responsible for the enhancement of the spontaneous polarization under the electric field and the dielectric constant. PL analysis also confirms that the Si-nitride film prepared with Ar/N2 (50/50) mixed gas flow contains more N vacancies than the Si-nitride film prepared with pure Ar gas flow.

Efficient MAPbI3 Perovskite Solar Cells Employing Sputtered p-Type NiOx Hole Transport Layer on Dependence of Oxygen Partial Pressure

In this paper, the effect of NiO x thin film prepared by a radio-frequency sputtering process under different oxygen partial (Ar:O2 ratio) pressures on the photovoltaic properties of planar-type MAPbI3 perovskite solar cells (PSCs) was investigated. The electrical, optical, morphological, and structural properties of sputtered NiO x thin films deposited under varied process oxygen gas condition are scrutinized. In particular, this study demonstrates that the properties of NiO x thin film with Ni3+/Ni2+ ratio are dependent on process oxygen gas condition. The influence of Ni vacancies on the chemistry and electronic structure of NiO x thin films is investigated using X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS). The sputtered NiO x thin film with lower Ni3+/Ni2+ ratio exhibits appropriate conductivity, hole mobility, high transmittance, and uniform surface morphology as well as a preferred in-plane orientation of the (220) plane under pure Ar gas atmosphere. When 5% (Ar:O2=19:1) or 10% (Ar:O2=18:2) oxygen is injected during the process, the conductivity of NiO x thin films with higher Ni3+/Ni2+ ratio is higher, but at the expense of optical transmittance. Additionally, this work exhibits the effect of perovskite active layer crystallinity and device performance using sputtered NiO x thin film under different oxygen partial pressures (Ar:O2 ratio) as hole transport layer for PSCs. The power conversion efficiency (PCE) of PSC obtains the highest PCE of 15.74% at the optimized NiO x thin film under pure Ar atmosphere. Compared to that, the efficiencies of the PSCs using the NiO x thin films processed at 5% and 10% oxygen partial pressure is 4.17% and 1.39%, respectively. Therefore, this study elucidate the effect of NiO x thin films deposited under different oxygen partial (Ar:O2 ratio) pressures on the performance of PSCs.

In-situ synthesis of oxides by reactive process atmospheres during L-PBF of stainless steel

Traditionally, reactive gases such as oxygen (O2) and carbon dioxide (CO2) have been avoided during laser powder bed fusion (L-PBF) of metals and alloys based on the notion that it may lead to defect formation and poor properties. Here we show that instead, these gases can be used to form sub-μm-sized oxide particles in-situ during the L-PBF process in an Fe-Cr-Al-Ti stainless steel and lead to improved room temperature and high-temperature mechanical properties. We manufactured cube samples using pure Ar and various reactive gas atmospheres, namely an O2/Argon (Ar) mixture containing 0.2 % O2 and CO2/Ar mixtures containing up to 100 % CO2. Co-axial measurements of infrared radiation emitted from the melt pool showed correlation to the presence of O2 or CO2 in the gas mixture. Builds produced under CO2-containing atmosphere contained complex oxides with an average diameter of ∼40 nm, an Al-rich core and a Ti-rich shell. Due to the high cooling rates typical to L-PBF, agglomeration of oxides and slag formation on the surface of the samples could almost be entirely avoided. Compression tests at temperatures up to 800 °C showed that the samples produced in 100 % CO2 have about 20 % higher yield stress compared to samples produced in Ar. The paper concludes with a discussion of the formation mechanism of the observed oxides. Our results show that in-situ reactions during additive manufacturing processes are a promising pathway to the synthesis of particle-reinforced alloys.

The evolution of microstructure and intergranular corrosion resistance of duplex stainless steel joint in multi-pass welding

Abstract This work focused on the microstructure and intergranular corrosion resistance of duplex stainless steel at different periods of multi-pass welding. Roots protected with pure Ar and Ar-N2 mixing gas were investigated. The austenite content of the root shielded by pure Ar raised with the increasing of welding layers, but its intergranular corrosion resistance was significantly deteriorated. The microstructure showed that much secondary austenite (γ2) formed after the root was reheated by the subsequent welding layer and in the final joint. Meanwhile, the results of the root shielded with Ar-3% N2 showed that its austenite content in the root of final joint was similar to the pure Ar shielded root, but its intergranular corrosion resistance was not obviously deteriorated in multi-pass welding process. It is suggested that a suitable austenite-ferrite phase ratio in the final DSS multi-pass joint cannot guarantee a good intergranular corrosion performance, the microstructural evolution process, e.g., the precipitation of chromium nitride and the formation of γ2, also affect the corrosion resistance.