Nitriding Treatment Research Articles

Effect of Combined Ion-Plasma Thermocyclic Nitriding and Magnetic Abrasive Treatment on the Fatigue Resistance of the EK61 Alloy

Effect of Combined Ion-Plasma Thermocyclic Nitriding and Magnetic Abrasive Treatment on the Fatigue Resistance of the EK61 Alloy

Technological Processes for Increasing the Cavitation Erosion Resistance of Nimonic 80A Superalloys.

Nickel-based superalloys are frequently used to manufacture the components that operate under cavitation erosion conditions, such as aircraft gas turbine construction, nuclear power systems, steam turbine power plants, and chemical and petrochemical industries. Their poor performance in terms of cavitation erosion leads to a significant reduction in service life. This paper compares four technological treatment methods to improve cavitation erosion resistance. The cavitation erosion experiments were carried out on a vibrating device with piezoceramic crystals in accordance with the prescriptions of the ASTM G32-2016 standard. The maximum depth of surface damage, the erosion rate, and the morphologies of the eroded surfaces during the cavitation erosion tests were characterized. The results indicate that the thermochemical plasma nitriding treatment can reduce mass losses and the erosion rate. The cavitation erosion resistance of the nitrided samples is approximately 2 times higher than that of the remelted TIG surfaces, approximately 2.4 times higher than that of the artificially aged hardened substrate, and 10.6 times higher than that of the solution heat-treated substrate. The improvement in cavitation erosion resistance for Nimonic 80A superalloy is attributed to the finishing of the surface microstructure, graining, and the presence of residual compressive stresses, factors that prevent crack initiation and propagation, thus blocking material removal during cavitation stresses.

Effect of Salt Bath Nitriding and Reoxidation Composite Texture on Frictional Properties of Valve Steel 4Cr10Si2Mo

In order to improve the service life of 4Cr10Si2Mo valve steel, laser processing technology was used to prepare triangular textures with different area occupancies on the surface of 4Cr10Si2Mo, and then 4Cr10Si2Mo was subjected to salt bath nitridation (salt bath temperature 580 °C) and oxidation (oxidation temperature 400 °C). The mechanism of composite surface treatment technology on friction and wear performance of valve steel was explored. The effect of triangular texture on working surface stress and hydrodynamic pressure was explored using simulation technology, and the mechanism of texture in friction was further studied. The XRD test results showed that after salt bath nitriding and reoxidation treatment, the surface of 4Cr10Si2Mo mainly contained Fe2N oxide film and Fe3O4 and other components. The XPS test showed that the nitriding layer contained Cr-N, and the surface hardness reached 710.5 HV0.5. The simulation results showed that introducing surface texture will increase the stress on the contact surface, especially near the texture. However, under lubricating conditions, the flow field in the textured lumen produces a wedge effect, which increases the oil film pressure. After salt bath nitriding composite texture treatment, the wear resistance of 4Cr10Si2Mo significantly improved under the synergistic effect of the nitrided layer dominated by the magnetite phase (Fe3O4) and the microtexture. Fe3O4 can reduce the friction coefficient and resist oxidation reactions. In addition, the texture of the area occupancy of the texture also affects the surface tribological properties. The texture with an area occupancy rate of 11.45% (low × high is 0.3 mm × 0.3 mm) had the best anti-friction effect, and the friction coefficient reduced by 65%.

Tribological Behavior of SINTER30 Steel Subjected to Duplex Treatment

Plasma nitriding has been extensively used to improve materials’ surface and mechanical properties using conventional plasma techniques. However, this process generally results in a nonuniformity of the properties. In the cathodic cage plasma nitriding (CCPN), the plasma is active only on the surface of the cathodic cage, eliminating inherent defects of conventional plasma nitriding. Herein, a duplex treatment, CCPN and TiN deposition, is used on SINTER30 tool steel for the first time. Vickers microhardness tests, X‐ray diffractometry, Raman scattering spectroscopy, and scratching tests characterize the samples. The results show that TiN post‐coating attains higher surface hardness. All the groups increase their microhardness properties when compared with nontreated substrates. The prior treatment of plasma nitriding assists hardening of the substrate surface. The best condition is obtained when the sample is placed inside the titanium cage and positions directly on the sample port, with simultaneous duplex treatment. When the substrate passes through this simultaneous duplex process, peaks corresponding to Fe3N and TiN are observed at Raman spectra. Suitable TiN layers improve the film adhesion, which is correlated to the system's load‐bearing capacity.

Tuning Fischer-Tropsch synthesis product distribution toward light olefins over nitrided Fe-Mn bimetallic catalysts

A series of Fe-Mn bimetallic catalysts with various pretreatment atmosphere including H2, CO and alternatively NH3, were employed for the Fischer–Tropsch synthesis (FTS). The structure of Fe-Mn bimetallic catalysts was revealed by using multiple characterization techniques, where Mössbauer spectra was used to define the iron species. With direct pretreatment, the reduction efficiency is in the sequence of H2 > CO > NH3. Fe-Mn bimetallic catalysts pre-reduced by H2 that permit an easy nitrogenation. To correlate the phase compositions of spent catalysts with FTS performance, the individual contribution of Fe, iron carbides (χ-Fe5C2, ε-Fe2(.2)C and θ-Fe3C) and iron nitride (Fe2N) to hydrocarbon selectivity was deconvolved by linear regression. It was discovered that C2=-C4= selectivity was proportional to the content of epsilon-iron carbide, which was promoted by the doping with Mn and further nitriding treatment. Successfully nitrided Fe-Mn bimetallic catalysts exhibit a better stability of C2-C4 O/P along time on stream, while either direct CO treatment or NH3 treatment followed by CO treatment result in a rapid decent of C2-C4 O/P ratio against time. Furthermore, Mn enhances long-chain hydrocarbon selectivity and suppresses CH4 formation, whereas the nitrogenation inhibits the chain growth ability, concentrating the hydrocarbon selectivity into C2-C4 fraction. Hence, the nitrided Fe-Mn catalyst is able to maintain a high light olefin selectivity. This study highlights that nitrogenation could provide an opportunity to tune the C2-C4 olefins by optimizing the phase structure of Fe-Mn catalysts.

Effect of carburizing and nitriding duplex treatment on the friction and wear properties of 20CrNi2Mo steel

In this study, the responses of 20CrNi2Mo steel to carburizing (C) and carburizing-nitriding (C + N) duplex treatment and the effects of these treatments on the friction and wear properties were systematically studied. The 20CrNi2Mo surface layers were characterized by optical microscopy (OM), laser scanning confocal microscopy (LSCM), x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Vickers microhardness tests and high-speed reciprocating friction and wear testing. The results showed that after the carburizing and nitriding duplex treatment, an approximately 5 μm thick compound layer (CL) consisting of the γ′-Fe4N and ε-Fe2-3N phases had formed on the surface, and the diffusion layer depth was approximately 220 μm. The carbides (MC) stored during carburizing were easily converted to nitrides (MN) during the nitriding process. Furthermore, the surface microhardness (879 HV) was increased by a factor of 2 compared with the substrate (420 HV), the surface residual compressive stress (−652 MPa) was increased significantly, and the surface roughness also increased. Wear analyses under different loads showed that specimen C exhibited the worst wear resistance, and its wear mechanism was mainly abrasive wear. The C + N with CL samples showed excellent wear resistance under a 20-N load; after removing the CL samples (C + N with CL), they showed excellent wear resistance under a 40-N load, and the wear mechanism was mainly adhesive wear. This work showed that the wear resistance was improved significantly by the carburizing and nitriding duplex treatment, but the CL had different effects on the wear performance under different loads.

Development of dual phase soft magnetic laminate for advanced electric machines

The development of dual phase soft magnetic laminate for advanced electric machines at General Electric is summarized, including alloy development, properties, manufacturing trials, prototype experience, potential applications, and future material development. Dual phase soft magnetic laminates provide the flexibility to tune magnetic/non-magnetic state at the desired locations, using solution nitriding treatment with protective mask/coating. This enabling material technology benefits electric machine performance by reducing flux leakage in the laminates. It also decouples the electromagnetic and mechanical design, which opens up the design space for advanced electric machines. Magnetic and mechanical properties of dual phase laminates were compared to commercial FeSi and FeCo soft magnetic laminates. Driven by the market needs for high power density and high-speed electric machines, a synchronous reluctance (SynRel) machine without PMs using dual phase soft magnetic laminates was assessed in machine electromagnetic performance as well as rotor stress analysis by finite element simulation. Successful prototype build and testing further retired manufacturing risks and advanced the technology maturity level. Future material development with higher mechanical strength, higher saturation magnetization, higher permeability, and lower loss are highly desired for ground and air transportation electrification.

In Situ Electrochemically Oxidative Activation Inducing Ultrahigh Rate Capability of Vanadium Oxynitride/Carbon Cathode for Zinc-Ion Batteries.

As a promising candidate for large-scale energy storage, aqueous zinc-ion batteries (ZIBs) still lack cathode materials with large capacity and high rate capability. Herein, a spherical carbon-confined nanovanadium oxynitride with a polycrystalline feature (VNxOy/C) was synthesized by the solvothermal reaction and following nitridation treatment. As a cathode material for ZIBs, it is interesting that the electrochemical performance of the VNxOy/C cathode is greatly improved after the first charging process viain situ electrochemically oxidative activation. The oxidized VNxOy/C delivers a greatly enhanced reversible capacity of 556 mAh g-1 at 0.2 A g-1 compared to the first discharge capacity of 130 mAh g-1 and a high capacity of 168 mAh g-1 even at 80 A g-1. The ex situ characterizations verify that the insertion/extraction of Zn2+ does not affect the crystal structure of oxidized VNxOy/C to promise a stable cycle life (retain 420 mAh g-1 after 1000 cycles at 10 A g-1). The experimental analysis further elucidates that charging voltage and H2O in the electrolyte are curial factors to activate VNxOy/C in that the oxygen replaces the partial nitrogen and creates abundant vacancies, inducing a conversion from VNxOy/C to VNx-mOy+2m/C and then resulting in considerably strengthened rate performance and improved Zn2+ storage capability. The study broadens the horizons of fast ion transport and is exceptionally desirable to expedite the application of high-rate ZIBs.

Study of Surface Modification of Niobium Caused by Nitriding and Cathodic Cage Deposition

In this work, plasma nitriding (PN) and cathode cage plasma deposition (CCPN) treatments were carried out with temperatures of 400 and 450 °C to evaluate the modifications caused on the surface of pure niobium samples. XRD, SEM, Vickers microhardness, and sphere-disk analyses were used to characterize the coatings’ composition, morphology, hardness, and wear resistance. The results showed that the treated samples increased hardness and wear resistance, with the sample submitted to CCPN at 450 °C presenting the best tribological behavior.

Development of complex hardening technology of cold rolling rolls by plasma surfacing

A comprehensive technology for hardening of mining and metallurgical equipment parts deposited by high-speed alloys is proposed, consisting of plasma surfacing, heat treatment, nitriding processes and ultrasonic treatment. The basis of the technology is the technological process of plasma surfacing in a protective-alloying environment of nitrogen with flux-cored wire, which makes it possible to obtain a deposited layer without cracks, pores and defects in macro- and microstructures with a average surface hardness of 56 HRC. The main contribution to the hardening of the deposited heat-resistant alloy is made by a fourfold tempering at a temperature of 560...580 °C. After surfacing and tempering, the hardness of the alloy increases to 62...64 HRC. The increase in hardness occurs due to the conversion of residual austenite into martensite, the release of carbides and carbonitrides. The contribution of nitriding and ultrasonic treatment processes to the hardening of the deposited alloy after tempering is 1...2 HRC.

To determine the effect of plasma nitriding treatment 56 on screw loosening and surface topography of different 78 implant-abutment screw systems with and without thermocycling: An in vitro study.

The aim of this study was to evaluate and compare the effect of plasma nitride-treated abutment screws of two different implant systems on screw loosening and surface topography with and without thermocycling. This was an in-vitro experimental study. Fifty-two abutment screws (Group A: 26 Genesis and Group B: 26 Bredent) underwent plasma nitride treatment and were subdivided into two groups, one without thermocycling and one with thermocycling. Dynamic load was applied and detorque values were evaluated for determining the screw loosening using "independent t-test" with the help of IBM SPSS Statistics 20 and scanning electron microscopy was done to check for surface topography. Inter- and intragroup comparisons were done using independent t-test (SPSS: Statistical Package for the Social Sciences software version 20). Plasma nitriding treatment genesis implant system abutment screw showed more screw loosening (P < 0.05) and surface roughness as compared to bredent with and without thermocycling. From the present study, it was shown that plasma nitride-treated abutment screws decreased the occurrence of screw loosening favoring the bredent implant-abutment system more than the genesis implant-abutment system.

Characterization and electrochemical behavior of a multilayer-structured Ti–N layer produced by plasma nitriding of electron beam melting TC4 alloy in Hank's solution

In this work, electron beam melting (EBM) titanium alloy were strengthened by carrying out a hollow cathodic plasma source nitriding treatment. The EBM-TC4 alloys were nitrided at 500 °C for 1, 3, and 5 h in an NH3 atmosphere. X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy was used to evaluate the microstructure and surface morphology of the samples. The nitrided layers formed on the EBM-TC4 alloy were identified as TiN, Ti2N, and nitrogen-stabilized α(N)–Ti phases. Potentiodynamic polarization and electrochemical impedance spectroscopy measurements were carried out to evaluate the electrochemical behavior of the samples in Hank's balanced salt solution. The relationship between the corrosion resistance of the nitrided layer and its microstructure was explored. Thus, the improved properties of the nitrided alloys can be attributed to the formation of a Ti–N layer composed of an outermost nanocrystalline/amorphous TiN layer and a crystalline TiN sub-layer on the top of the Ti2N crystal layer. The novel Ti–N layer structure with improved corrosion resistance provides broad opportunities for the application of commercial Ti alloys and improving their durability.

Investigations of Fatigue Damage in a Nitriding Low-Carbon Bainitic Steel for High-Performance Crankshaft

In the automotive environment, the need to increase the performance of materials requires extra engineering efforts. The possibility of developing new materials is strategically important. Indeed, alternative solutions in terms of material choice allow designers to optimise their projects and keep competitive production costs. Traditional quenched and tempered steels are usually used for highly stressed components, and possible alternatives could be important competitive opportunities. One possible substitute is using bainitic steels to exploit their economic advantages while maintaining acceptable mechanical performances. This paper explores the fatigue life behaviour of a new low-carbon bainitic steel for applications requiring case hardening treatment obtained by the nitriding process. A high-cycle fatigue (HCF) strength assessment is conducted through a test campaign to compare treated and untreated material. The improvement in fatigue strength is evaluated as well as the study of fracture surfaces, residual stress, and microhardness profiles to assess in detail the effectiveness of the nitriding process. It is found that the nitriding leads to an improvement in fatigue life but not as much as expected because of the low ductile behaviour of this steel, the high speed of stress application added, and the embrittlement of the nitriding treatment, as confirmed through fracture surface analysis.

Surface reconstruction and charge distribution enabling Ni/W5N4 Mott-Schottky heterojunction bifunctional electrocatalyst for efficient urea-assisted water electrolysis at a large current density

Urea-assisted water electrolysis is regarded as an energy-efficient strategy for hydrogen production, but its potential use is still limited by sluggish kinetics in both anodic urea oxidation reaction (UOR) and cathodic hydrogen evolution reaction (HER). Herein, we report the facile synthesis of nickel foam (NF) supported Ni/W5N4 Mott-Schottky heterojunction nano-microspheres as a highly active catalyst for both UOR and HER using a hydrothermal method followed by nitridation treatment. The as-prepared Ni/W5N4/NF catalyst with high electrochemically active surface area would reconstruct under oxidizing condition to form nickel tungsten oxyhydroxides to efficiently drive UOR, with a potential of only 1.34 V (versus reversible hydrogen electrode) at 10 mA cm−2. Impressively, thus-prepared catalyst benefited from charge redistribution only required an overpotential of 25 mV at 10 mA cm−2 for HER. In particular, the Ni/W5N4/NF catalyst couple used for urea-assisted water electrolysis just needed a cell voltage of 1.77 V at 1000 mA cm−2.

Achieving highly efficient pH-universal hydrogen evolution by Mott-Schottky heterojunction of Co2P/Co4N

A vital step towards sustainable hydrogen production is to develop high-efficiency electrocatalysts for pH-universal hydrogen evolution reaction (HER). Modulation of the electronic structure of electrocatalysts by constructing Mott-Schottky heterojunction could be regarded as an effective strategy to promote the electrochemical performances. Herein, we report hybrid Mott-Schottky electrocatalyst composed of metallic Co4N and n-type semiconducting Co2P,fabricated via the hydrothermal method followed by the subsequent phosphating and nitriding treatment. Due to the Mott-Schottky effect, the self-driven charge carriers transfer occurs at the heterointerfaces of Co2P/Co4N, leading to a built-in electric field, accelerated charge transfer rate, and improved chemisorption free energies of the reaction intermediates, ultimately boosting the dissociation of water molecules. Therefore, the as-prepared Co2P/Co4N electrocatalyst exhibits outstanding pH-universal HER performance with extremely low overpotentials of 53, 19, and 32 mV at a current density of 10 mA cm−2 in 0.5 M H2SO4, 1 M phosphate buffer solution (PBS), and 1 M KOH electrolytes, respectively. Further, the electrocatalyst reveals low Tafel slopes of 38, 26, and 50 mV dec−1, which outperform those of the previously reported Co-based catalysts. Density functional theory (DFT) calculations clarify that the Schottky contact can regulate the adsorption energy of water, and the electronic structure at interface of the heterojunction weakens the hydrogen adsorption free energy (ΔGH*) of Co2P/Co4N to nearly zero, which is the reason for the addressed splendid HER performance.

Electrical Performance of 28 nm-Node Varying Channel-Width nMOSFETs under DPN Process Treatments.

The decoupled-plasma nitridation treatment process is an effective recipe for repairing the trap issues when depositing high-k gate dielectric. Because of this effect, electrical performance is not only increased with the relative dielectric constant, but there is also a reduction in gate leakage. In the past, the effect of nitridation treatment on channel-length was revealed, but a channel-width effect with that treatment was not found. Sensing the different nano-node channel-width n-channel MOSFETs, the electrical characteristics of these test devices with nitridation treatments were studied and the relationship among them was analyzed. Based on measurement of the VT, SS, Gm, ION, and IOFF values of the tested devices, the electrical performance of them related to process treatment is improved, including the roll-off effect of channel-width devices. On the whole, the lower thermal budget in nitridation treatment shows better electrical performance for the tested channel-width devices.

Investigation on the machinability of nitriding mold steel by applying in-situ laser assisted diamond cutting

Mold steel is a typical material in precision molding for the massive production of optical lenses. It has the outstanding mechanical properties and superior corrosion resistance. However, it is a huge challenge for ultra-precision diamond cutting mold steel due to the active chemical affinity between the diamond tool and steel, which causes the deteriorated surface integrity and catastrophic tool wear. In this research, we adopted a novel hybrid machining technology, which is in-situ laser assisted diamond cutting (In-situ LADC), for ultra-precision machining nitriding mold steel. Pulsed plasma nitriding treatment provides a dense nitrided compounds layer in workpiece surface to suppress the chemical reaction between the iron atom of steel and carbon atom of diamond. Furthermore, the surface nitriding layer is softened by the laser radiating to improve the machinability of workpiece. Experimental results showed that the laser thermal effect obviously decreased the hardness and elastic modulus of nitrided layer, which enhanced the material removing in ductile mode. Compared with the ordinary cutting (OC), the machined surface roughness Ra is decreased from 29 nm to 12 nm. The maximum profile error PV is also decreased from 161 nm to 64 nm. The mechanism of tool wear was changed from the rapidly abrasive wear to mildly adhesive wear, which significantly increased working life by 29 %.

First-principles analysis on the nitrogen adsorption and diffusion in Ti alloy towards clarified diffusion mechanism in nitriding

Based on first-principles calculations, the adsorption and diffusion of the nitrogen atoms in Ti bulk and Ti surface layer were studied. Al doping is considered in the study of the surface layer. We first calculated and studied N in bulk Ti and obtained that the N atom preferentially occupies the octahedron(O) interstice of the α-Ti bulk, which behaves as a metallic N-containing solid solution at a lower N concentration. And the diffusion energy barrier is the lowest in the α-Ti bulk when it diffuses between two O sites along with the （1¯ 2 1¯ 0）direction. Then we studied N adsorption and diffusion of N on the α-Ti(0 0 0 1) surface. The N atoms are predicted to be adsorbed on the FCC and HCP sites of the Ti(0 0 0 1) surface, where the FCC site has lower Ead (adsorption energy). In addition, after doping Al atoms on the Ti surface and sub-surface, the adsorption capacity of the N atom decreases. Especially when the Al atom exists on the Ti surface, this effect is very significant. And the Al atom also reduces the stability of the N atom in the subsurface O site at the same time. Finally, the diffusion process of N atoms from the surface to the subsurface was calculated and compared with and without Al doping. This paper provides fundamental insights into the diffusion mechanism in the nitriding treatment of titanium alloys. These calculation results can infer which titanium alloy is more suitable for nitriding.

Influence of plasma nitriding treatment on the micro-scale abrasive wear behavior of AISI 4140 steel

• Nitriding treatment leads to a reduction in the volume of wear and the specific wear coefficient. • Nano nitrides phases formed on the surface of the material. • Microstructural parameters and the number of phases influence the micro-abrasive wear behavior. • The hard layer of nitrides increased the AISI 4140 steel hardness more than 2.5 twice. Plasma nitriding was performed on AISI 4140 steel for various times. Untreated and plasma nitrided AISI 4140 steel were microstructurally, mechanically and tribologically characterized. The nitrided compound layer, consisting of ε-Fe 2-3 N and λ-Fe 4 N phases, was approximately of 5.0 μm thick. Microhardness of treated steel for 3 h was significantly higher than that of the untreated. The ball cratering test revealed that abrasivity of the treated samples decreased with the nitriding time due to an increasing in micro-strain values, quantify of nitrided phases, and the formation of nanocrystalline size of nitrides.

The influence of plasma nitriding hardness treatment on the dynamic compressive behavior of the Hardox 400 at a wide temperature range

This paper aims to study the effect of hardness nitriding treatment on the overall mechanical behavior of Hardox 400 steel. A Plasma Immersion Ion Implantation (PIII) technique was used for material nitriding while a split Hopkinson pressure bar equipped with an electromagnetic heating system was used for the thermomechanical characterization of the studied steel. The collected data are analyzed to identify the combined effect of the high strain rates and elevated temperatures on the flow stress and ductility. The microstructure and the physical properties of the nitrided Hardox 400 were studied using scanning electron microscopy (SEM), X-ray diffraction, and nano-indentation tests. Although the increase of the surface hardness by 37%, the quasistatic and dynamic compression tests showed a decrease in the flow stress due to the microstructure modification caused by the increase of the temperature during the plasma nitriding process. For a better assessment of the experimental results, reduction factors for the main mechanical properties are reported. The test data from SHPB indicated a dependency of the strain rate to the temperature of untreated un-nitrided Hardox 400. Finally, a critical review of the well-known Johnson-Cook constitutive model is highlighted, where material parameters are calibrated with special attention to the thermal softening parameter. The obtained results could be of great interest for the assessment of structural components’ robustness where the combined strain rate and temperature for Hardox 400 are met.