Plasma Electrolytic Carbonitriding Research Articles

Study on preparation and friction characteristics of steel 1045 modified layer based on plasma electrolytic carbonitriding

The structure and characteristics of steel 1045 with anode plasma electrolytic carbonitriding (PEN/C) have been studied. Taking the 280 V, 20% carbamide, 5% NH 4 Cl and 5 min treatment as basic sample condition, the influence of different voltage, treatment time, and carbamide content on the characteristics of the permeable layer was explored. The modified layer was analyzed by SEM, XRD and hardness tests. The friction performance was evaluated using a ball-disk friction and wear tester. The study found that the modified layer was mainly composed of iron nitride and iron carbide. With the change of the preparation parameters, the main influence was the ratio of the two elements in the iron nitride. Within a certain range, voltage and reaction time were directly proportional to the thickness of the modified layer. Meanwhile, the increase in voltage and the increase in treatment time would increase the martensite content and carbon and nitrogen compounds, which would increase the hardness of the modified layer. The maximum hardness was reached at a reaction time of ten minutes, and the value was 889.5 HV, which was about four times the hardness of the substrate. After treatment, the surface friction coefficient and the degree of wear were greatly reduced. The corresponding friction coefficient of basic sample condition was 0.2, and the loss of wear was 0.3 mg which is 3.3 times less than substrate. • Anode plasma electrolytic saturation has an efficient heating rate and is environmentally friendly. • Anode plasma electrolytic carbonitriding can greatly increase the hardness of the sample surface, thereby greatly reducing friction coefficient. • Voltage and time have a greater impact on the hardness of the modified layer. • Proper experimental parameters can greatly reduce the wear degree of the surface

Study on Preparation and Friction Characteristics of Steel 1045 Modified Layer Based on Plasma Electrolytic Carbonitriding

Study on Preparation and Friction Characteristics of Steel 1045 Modified Layer Based on Plasma Electrolytic Carbonitriding

Phase Composition and Thin Structure of Steel Surface after Plasma Electrolytic Carbonitriding

Using the transmission electron microscopy of thin foils the paper studies the phase composition and fine structure of 0.18С–1Cr–3Ni–1Mo–Fe steel after plasma electrolytic carbonitriding carried out through the surface saturation with nitrogen and carbon. The steel specimens are studied before and after carbonitriding on the surface and at a ~40 μm distance from the surface. It is found that carbonitriding causes significant qualitative and quantitative changes in the steel structure. Thus, the layers of residual austenite appear along the boundaries of martensitic lamellas, and the particles of alloyed cementite and carbonitrides are observed inside the lamellas. The layers of residual austenite locate at a ~40 μm depth along the boundaries of all martensitic crystals, while inside the crystals there are only particles of alloyed cementite and carbonitride M23(C, N)6. The control parameter of changes in the structure and phase composition is the concentration of interstitial atoms of carbon and nitrogen. Changes in this concentration lead to the system deviation from thermodynamic equilibrium. The transition of system to equilibrium or quasi-equilibrium states is considered to be performed through the transition of crystal lattices, which form a gradient structural-unstable state of the matrix, intermetallics and carbonitride compounds, to a low-stability state.

Effect of rare earth elements on plasma electrolytic carbonitriding of Ti–6Al–4V alloy

ABSTRACTThe paper aims to research the effect of rare earth elements on the carbonitriding layer of titanium alloy by establishing a theoretical model between rare earth concentration and atomic diffusion efficiency. It shows that adding rare earth can not only refine the discharge holes, but also reduce surface cracks, which significantly improve the surface quality of the strengthening layer. It is also found that an appropriate amount of rare earth can greatly increase the growth rate of the carbonitriding layer and carbon content near the surface. Furthermore, compared with the conventional plasma electrolytic carbonitriding treatment, adding 2 g L−1 cerium oxide can effectively reduce the activation energy of carbon, so as to improve its diffusion ability.

Investigation of anodic plasma electrolytic carbonitriding on medium carbon steel

In this paper, anodic plasma electrolytic carbonitriding (APEC/N) treatment was employed to fabricate a hardened layer on medium carbon steel. The optical emission spectroscopy (OES) and the acoustical signal characterizations of plasma discharge during APEC/N process were analyzed for the first time. The results showed that the discharge plasma was in a local thermal equilibrium (LTE) state and the electron temperature in discharge zone was 4000K–8000K. The high electron temperature and strong acoustical signal corresponded with the intense discharge process, while the high-frequency noise up to 20KHz related to the discharge taking place. Beneath the oxide layer, there was a 60μm thick carbonitrided layer, which contained Fe3C and Fe4N phases. After APEC/N treatment, the wear resistance of medium carbon steel was improved. The wear rate of treated steel was about 2.61×10−4mm3/N·m, which was only half of the bare steel substrate.

Anti-corrosion layer prepared by plasma electrolytic carbonitriding on pure aluminum

In this paper, plasma electrolytic carbonitriding (PEC/N) method was applied to pure aluminum for the first time. The spectroscopic characterization of plasma discharge during PEC/N process was analyzed and the electron temperature was calculated in terms of optical emission spectroscopy. The results showed the discharge plasma was in local thermal equilibrium (LTE) state. Electron concentration and electron temperature were about 6×1021m−3 and 4000K, respectively. The carbonitrided layer contained Al4C3, AlN and Al7C3N3 phases. After PEC/N treatment, the corrosion resistance of pure aluminum was significantly improved, which was related to the formation of nitride phases. This work expands the application of plasma electrolysis technology on the surface modification of low melting point metal.

Corrosion and bio-tribological properties of Ti(CN)x hard coating on titanium alloy by the pulsed plasma electrolytic carbonitriding process

Ti(CN)x hard coating was deposited on Ti6Al4V alloy by the pulse plasma electrolytic carbonitriding process in formamide electrolyte. The influence of pulse frequency on the corrosion and bio-tribological properties of PEC/N coating was investigated. The results showed that higher pulse frequency (15kHz) provides a denser diffusion layer than low frequency markedly improving the corrosion resistance. The thickness and hardness of diffusion layers increase with decreasing pulse frequency and the wear resistance gets improved under dry friction. Carbonitriding layers greatly improve the bio-tribological behavior of Ti6Al4V alloy under saline and calf serum lubrication. The friction coefficient is reduced to 0.23 under calf serum lubrication and the wear rate decreases by two orders of magnitude compared with titanium alloy.

Characterization of submicron-size layer produced by pulsed bipolar plasma electrolytic carbonitriding

Abstract The feasibility of developing a submicron-size layer on nitriding steel using pulsed bipolar plasma electrolytic techniques was investigated. Plasma electrolysis was performed in duty cycle of 80% and process duration of 600 s, with an electrolyte composition of 85.8 wt% urea, 12 wt% water and 2.2 wt% sodium carbonate. It was found that this technique reduces the grain size in both compound and diffusion layers. The average grain size of about 110 nm was observed in the white layer. The presence of Fe3O4 phase in low frequencies was confirmed by X-ray studies. γ′-Fe4N rather than e-Fe2-3N was found to be the dominant phase at higher frequencies. The results suggest that the size of the cavities formed on the surface is reduced to 300 nm. Characterization of the corrosion behavior of the layer by electrochemical impedance spectroscopy technique revealed that the capacitive properties of the surface layer (Cc) in samples processed at high frequencies were reduced. Hence, it showed better corrosion resistance compared to the samples processed at low frequencies.

Effect of C/N Concentration Fluctuation on Formation of Plasma Electrolytic Carbonitriding Coating on Q235

The plasma electrolytic carbonitriding (PEC/N) on the Q235 steel was investigated in an aqueous solution containing monoethanolamine and KCl in a very short period of time. The microdischarge characteristics of the voltage/current on the Q235 were observed using real-time imaging during the PEC/N. The microstructure and element distribution of the carbonitriding layer were examined using scanning electron microscope (SEM) equipped with energy dispersive spectroscope (EDS). The effect of microdischarge on roughness, thickness and microhardness was evaluated. The formation of the carbonitriding layer was discussed. Research shows that it is similar in the microstructure and properties between the plasma electrolytic carbonitriding and the traditional gas carbonitriding. The formation of the carbonitriding layer results from the carbon and nitrogen fluctuation in PEC/N process. The microhardness and thickness can be up to HV 779 and 0.360 mm in 180 s, respectively, which is close to the results of the gas carbonitriding in the microhardness. Therefore, the plasma electrolytic carbonitriding has a potential to substitute the gas carbonitriding.

Characterization of Pure Titanium and Ti6Al4V Alloy Modified by Plasma Electrolytic Carbonitriding Process

Porous nanocrystalline thick Ti (CxN1-x) films which bond firmly to the substrate are obtained on commercially pure titanium and Ti6Al4V alloy by plasma electrolytic carbonitriding (PECN) treatment. The microstructures and compositions of the modified layer on different substrates were compared. The results showed that the modified layer is composed of the outer Ti (CxN1-x) film and the diffusion layer. When discharge-treated for 150 min, the thickness of the Ti (CxN1-x) film is ~15μm, irrespective of the different substrate. The TiH2 riched diffusion layer which is 40-45μm thick is located beneath the Ti (CxN1-x) film for the pure titanium substrate, while for Ti6Al4V alloy it is the β-Ti-riched layer which is ~100 μm thick.

Preparation and properties of TiCxN1 − x coatings containing calcium on titanium surface by plasma electrolytic carbonitriding

The TiCxN1−x coatings containing calcium (Ca–TiCxN1−x) were prepared on the surface of titanium through plasma electrolytic carbonitriding (PEC/N) technique in a certain concentration of electrolyte solution of triethanolamine, urea and calcium nitrate. The effects of parameters, such as discharge time, on the Ca–TiCxN1−x coatings were investigated, and the phase composition, morphologies, surface chemical components, anticorrosion and hardness were also examined, respectively. The results show that the plasma discharge time significantly affects the microstructure and composition of the coatings. In addition, introduction of the Ca–TiCxN1−x coatings into the Ti surface can clearly improve the wear resistance and anticorrosion. Moreover, MTT assay demonstrates that the Ca–TiCxN1−x coatings can improve the cell viability, showing excellent cytocompatibility.

Mechanical Performances of Carbonitriding Films on Cast Iron by Plasma Electrolytic Carbonitriding

The plasma electrolytic carbonitriding (PEC/N) process is applied to cast iron using an aqueous solution of acetamide and glycerin as the electrolyte. Mechanical properties of the carbonitriding layers on cast iron are investigated. After the PEC/N treatment, the microhardness and wear resistance of cast iron are improved significantly compared to the untreated substrate. When the substrate is processed at 350 V for 60s, the coating presents the highest microhardness and it is about 554.14HK0.02, and the coating with the highest hardness has the best wear resistance.

Plasma Electrolytic Carbonitriding of 20CrMnTi Steel

A carbontirided layer was produced on 20CrMnTi steel by plasma electrolytic carbonitriding (PEC/N). Scanning electron microscopy with an energy dispersive X-ray analysis was employed to study the morphology and chemical composition of the carbonitrided layer. Hardness of the layer was measured using a microhardness tester, and the phase structure was determined by X-ray diffraction. The results show that a compact carbonitrided layer can be obtained on the surface of 20CrMnTi steel. The thickness of the layer increases with carbontriding time. When the sample was treated at 120V for 20min, the thickness is 45μm and the highest microhardness is 766HV0.05. The carbontrided layers are composed of Fe3C, Fe5C2, ε-Fe3N and α-Fe.

Study of anodic voltage on properties of complex nanocrystalline carbonitrided titanium fabricated by duplex treatments

Up to the fourth moment distribution of carbonitride nanocrystallites produced by duplex treatments of surface nanocrystallisation and bipolar pulsed plasma electrolytic carbonitriding on commercially pure titanium was investigated by means of high precision figure analysis. Skewness and kurtosis of Gussian distribution curves have been studied, and the effect of anodic voltage peak has been determined. The usage of lower peaks of anodic voltage is more suitable for achieving lower sizes of carbonitride nanocrystallites. Surface roughness of treated samples was measured, and it has been observed that there is an optimum level of anodic voltage peak for surface roughness increasing (difference between two measured data).

Effect of electrolyte temperature on the nano-carbonitride layer fabricated by surface nanocrystallization and plasma treatment on a γ-TiAl alloy

The distribution of nano-carbonitrides produced by the treatments of surface nanocrystallization and plasma electrolytic carbonitriding on a γ-TiAl was investigated by means of figure analysis. The skewness and kurtosis of Gaussian shape distribution curves were studied and the effect of electrolyte temperature was determined. The usage of lower temperatures of the electrolyte is more suitable for achieving lower sizes of complex nano-carbonitrides. The surface roughness of treated samples was measured and it was observed that there is an optimum level of electrolyte temperature for surface roughness increase (difference between two measured data).

Microstructure and Corrosion Performance of Carbonitriding Layers on Cast Iron by Plasma Electrolytic Carbonitriding

The surface carbonitriding of cast iron is investigated in an aqueous solution of acetamide and glycerin. Microstructure, chemical and phase composition and corrosion performance of the carbonitriding layers are investigated by scanning electron microscopy, energy dispersive spectroscopy and x-ray diffraction, as well as potentiodynamic polarization testing. X-ray diffraction results show that the carbonitriding coatings are composed of martensite, austenite(γ-Fe), Fe2C, Fe3C, Fe5C2, FeN and ∊-Fe2−3N. After the plasma electrolytic carbonitriding treatment the corrosion resistance of cast iron is clearly improved compared to the substrate, and the coatings produced at 350 V for 30s give the best corrosion resistance.

Improvement of Surface Characteristics by Electroplating Hard Chromium Coating Post Treated by Nanocrystalline Plasma Electrolytic Carbonitriding

AbstractNanocrystalline carbonitrides were performed by pulsed plasma electrolytic carbonitriding on hard chromium coating deposited on AISI 1035 substrate by electroplating. The electroplated samples were connected cathodically to a high‐current pulsed power supply and biased to a negative voltage. The treatment times were 30, 60 and 60 min. A thick compound layer was formed on the surface of Cr coating with microhardness of about 1 200 HV0.15. The nanostructure of the treated layers depends strongly on the applied voltage. The wear resistance of the treated layers depended on process parameters. Overall mechanical properties of treated samples show strong relation to morphology and distribution of complex carbonitride nanocrystallites.

EFFECT OF PULSE DUTY CYCLE ON PROPERTIES OF HARD NANOCRYSTALLINE SURFACE FABRICATED BY DUPLEX TREATMENTS

Up to fourth moment distribution of carbide nanocrystallites produced by duplex treatments of surface nanocrystallization and pulsed plasma electrolytic carbonitriding on AISI 1010 mild steel was investigated by the means of figure analysis with high precision. Skewness and kurtosis study of the Gaussian distribution have been studied and the effect of duty cycle of pulsed current has been determined. The usage of lower duty cycles of pulsed current is more suitable for achieving lower sizes of carbide nanocrystallites. Surface roughness of treated samples was measured and it has been observed that there is an optimum level of duty cycle of pulsed current for surface roughness increasing (difference between two measured data).

Corrosion protection study of nanocrystalline plasma-electrolytic carbonitriding process for CP-Ti

The effect of various nanocrystalline plasma-electrolytic carbonitriding of a commercially pure titanium in a glycerol bath with various additives, such as carbamide, sodium nitrate, and triethanolamine, was studied. Effects of the bath composition on chemical composition and corrosion resistance of the PEC/N films were examined by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) in Ringer solution. The results showed that the films obtained in solutions with triethanolamine (T-film) had better corrosion resistance. A design of experiment (DOE) technique according to the Taguchi method, was used to optimize the process. The design was constituted of four factors, namely, triethanolamine concentration, electric conductivity of the bath, applied voltage, and duration of the process), each containing three levels.An analysis of the mean of signal-to-noise (S/N) ratio indicated that the corrosion resistance of plasma-electrolytically carbonitrided (commercially pure) Titanium was influenced significantly by the levels in the Taguchi orthogonal array. The optimized coating parameters for corrosion resistance are 1060 g/l for triethanolamine concentration, 360 mS/Cm for electric conductivity of the electrolyte, 260 Volts for applied voltage, and 9 minutes for treatment time. The percentage of contribution for each factor was determined by the analysis of variance (ANOVA). The results showed that the applied voltage is the most significant factor affecting the corrosion resistance of the coatings.

STUDY OF PULSE ON PULSED NANOCRYSTALLINE PLASMA ELECTROLYTIC CARBONITRIDING ON THE NANOSTRUCTURE OF COMPOUND LAYER

Surface hardening of commercially pure titanium by using pulse on pulsed nanocrystalline plasma electrolytic carbonitriding has been studied in this investigation. Coating process has been performed on Triethanolamine-based electrolyte by cooling bath. Nanostructure of obtained compound layer was examined with figure analysis of SEM nanographs. The effects of process variables, i.e., Triethanolamine concentration, electrical conductivity of electrolyte, applied voltage, and treatment time, have been experimentally studied. Statistical methods were used to achieve the optimum size of nanocrystals. Finally the contribution percentage of effective factors of pulsed current was revealed and confirmation run show the validity of obtained results.