Plasma Nitriding Parameters Research Articles

Investigation of the Combined Effects of Stress Concentrations and Plasma Nitriding Parameters on the Fatigue Performance of AISI 4140 Low Alloy Steel

Investigation of the Combined Effects of Stress Concentrations and Plasma Nitriding Parameters on the Fatigue Performance of AISI 4140 Low Alloy Steel

Study of the Wear Resistance Plasma Nitrided GGG60 by Optimization of Surface Treatment Conditions Using Response Surface Methodology

AbstractIn this study, the wear performance of spheroidal graphite cast iron subjected to plasma nitriding at different temperatures and treatment durations was investigated. The plasma nitriding parameters were optimized by response surface methodology (RSM) due to the output performance. Plasma nitriding was applied at three different temperatures (400, 450, 500 °C) and three different heat treatment durations (0.5, 2, 4 h). Wear tests were performed by ball-on-disk method for 60 minutes and for three different wear loads (10, 20, 30 N). The specimens were investigated for hardness, microstructure and wear performance. The RSM model was then created by using the wear resistance features. Plasma nitriding showed better wear performance than the untreated specimen for all treatment conditions. Hardness, nitrided layer thickness and wear performance remarkably improved with increasing temperature and process duration. The parameter that affects volume loss the most is wear load with 70.66% according to RSM modeling results. The most effective parameter in the wear rate change was found to be treatment duration at 42.85%. The model was able to predict the results with an error of 2.11% for volume loss and 9.14% for wear rate. The prediction results are very close to the experimental results. This clearly shows that the model can be used to determine the plasma nitriding parameters.

Enhanced plasma nitriding efficiency and properties by severe plastic deformation pretreatment for 316L austenitic stainless steel

In order to enhance the plasma nitriding efficiency and improve the hardness and wear resistance of 316L austenitic stainless steel, severe plastic deformation was adopted prior to plasma nitriding. The microstructure, phase constituents, hardness and wear resistance samples after plasma nitriding were determined by metallographic microscope, X-ray diffractometer, microhardness tester and universal friction and wear tester. The results showed that severe plastic deformation had significant enhancement effect on plasma nitriding efficiency. Under the same plasma nitriding parameters of 420 °C and 4 h, the thickness of nitriding layer was increased from 6.36 μm to 14.10 μm, more than twice thicker enhanced by severe plastic deformation. XRD confirmed that the nitriding layer is consisted of S phase. Meanwhile, the surface hardness was improved from 990HV to 1110 HV and with moderated gradient of cross sectional hardness; more valuably, the wear resistance was greatly enhanced by severe plastic deformation.

Enhanced surface properties of M2 steel by plasma nitriding pre-treatment and magnetron sputtered TiN coating

AISI M2 high-speed steels are widely used in cutting/forming tools due to their easy machinability and balanced toughness. Unfortunately, they exhibit severe cutting edge wear, which reduces their useful lifetime. The lifetime of such steels can be improved by titanium nitride hard coating. However, in sliding wear applications having a metal-to-metal contact, such coatings exhibit low adhesion to the substrate due to substantial hardness differences among coating and substrate. Here, plasma nitriding is performed before the deposition of magnetron sputtered-TiN coating using various nitriding parameters to find whether the surface properties of the duplex treated sample can be altered by changing these parameters or not. It is found that the surface hardness and hardening depth can be improved by using the duplex treatment as compared to only TiN coating. A significant decrease in wear rate is attained using the duplex treatment and substantial improvement by altering the plasma nitriding parameters.

Enhanced surface properties of M2 steel by plasma nitriding pre-treatment and magnetron sputtered TiN coating

AISI M2 high-speed steels are widely used in cutting/forming tools due to their easy machinability and balanced toughness. Unfortunately, they exhibit severe cutting edge wear, which reduces their useful lifetime. The lifetime of such steels can be improved by titanium nitride hard coating. However, in sliding wear applications having a metal-to-metal contact, such coatings exhibit low adhesion to the substrate due to substantial hardness differences among coating and substrate. Here, plasma nitriding is performed before the deposition of magnetron sputtered-TiN coating using various nitriding parameters to find whether the surface properties of the duplex treated sample can be altered by changing these parameters or not. It is found that the surface hardness and hardening depth can be improved by using the duplex treatment as compared to only TiN coating. A significant decrease in wear rate is attained using the duplex treatment and substantial improvement by altering the plasma nitriding parameters.

Effects of shot peening pre-treatment and plasma nitriding parameters on the structural, mechanical and tribological properties of AISI 4140 low-alloy steel

In recent years, hybrid surface treatments which include plasma nitriding combined with pre-shot peening operations have been proposed for the improvement of nitriding efficiency. The main objective of this study is to characterize the effects of dual process on the friction and wear behavior of metallic materials. For this purpose, AISI 4140 steel samples were shot peened at various densities of 16, 20 and 24 A. The pre-treated samples were plasma nitrided at a temperature of 500 °C for 1 and 4 h. The structural and mechanical properties of samples were analyzed by XRD, SEM and microhardness tester. Wear tests were performed under dry sliding conditions to determine the tribological properties of the samples. This study showed that the shot peening treatment formed finer grains, compressive residual stresses on the surface and increased the diffusion kinetics of the samples. The surface hardness and residual stresses increased with increasing shot peening density. It was evidence that the finer grains, increased dislocation density and surface defects increased the case depth obtained from plasma nitriding by enabling easier diffusion of nitrogen. The depth of the diffusion zones in shot peened plus plasma nitrided specimens was found almost two times thicker than that of the diffusion zones in specimens treated only by plasma nitriding. The highest surface hardness values were obtained from pre shot peened and plasma nitrided samples in consequence of the interactive effect from nitride phases/layers and increased surface compressive residual stress. As a result, pre-shot peened plus plasma nitrided samples exhibited higher wear resistance than specimens treated only by shoot peening and hybrid treating in glow a discharge atmosphere.

Influence of plasma glow discharge on nitriding process of technical titanium

Purpose: This article compares selected properties of surface layers produced by plasma nitriding. Additionally, the temperature at the onset of the production of surface layers with uniform characteristics over the entire sample surface was determined. Design/methodology/approach: The selected properties of the surface layers were compared using the following test methods: microhardness measurement by the Knoop method, GDEOS profile analysis, XRD analysis, topography analysis. Findings: It was found that nitriding in plasma glow discharge at 700°C results in obtaining homogeneous surface layers over the entire surface of the sample Research limitations/implications: The ion nitride processes did not allow a complete reduction in the oxygen content. Practical implications: The adopted plasma nitriding parameters will allow homogeneous properties of the surface layers over the entire surface of the sample to be obtained. Originality/value: The effect of plasma glow discharge on the properties of surface layers was determined.

Effect of plasma nitriding parameters on corrosion performance of 17-4 PH stainless steel

ABSTRACTThis study investigates the effect of plasma nitriding parameters on corrosion susceptibility of 17-4 PH stainless steel in 3.5 wt-% NaCl solution. In this regard, 17-4 PH stainless steel was plasma nitrided at 400°C for 5 and 10 h, 450°C for 5 h and 500°C for 5 h. Cross-sectional images after nitriding process showed that a uniform nitrided layer has been formed on steel substrate. Depending on the temperature and time of the nitriding process, different phases were formed in the nitrided layer. This affected general corrosion and pitting corrosion performance of 17-4 PH stainless steel in 3.5 wt-% NaCl solution. While precipitation of chromium nitrides for nitrided specimens at 450°C and higher increased the susceptibility to pitting and general corrosion, formation of expanded martensite (EM) in nitriding at 400°C improved the pitting corrosion resistance of 17-4 PH stainless steel. This is believed to be due to the release of nitrogen atoms from EM phase to form ammonium ions and increase the pH of the solution, supressing pit growth.

Evaluation of the Effect of Different Plasma-Nitriding Parameters on the Properties of Low-Alloy Steel

This work is concerned with the surface treatment (ion nitriding) of different plasma-nitriding parameters on the characteristics of DIN 1.8519 low-alloy steel. The samples were nitrided from 500 to 570 °C for 5–40 h using a constant 25% N2-75% H2 gaseous mixture. Lower temperature (500–520 °C) favors the formation of compound layers of γ′ and e iron nitrides in the surface layers, whereas a monophase γ′-Fe4 N layer can be obtained at a higher temperature. The hardness of this layer can be obtained when nitriding is performed at a higher temperature, and the hardness decreases when the temperature increases to 570 °C. These results indicate that pulsed plasma nitriding is highly efficient at 550 °C and can form thick and hard nitrided layers with satisfactory mechanical properties. The results show the optimized nitriding process at 540 °C for 20 h. This process can be an interesting means of enhancing the surface hardness of tool steels to forge dies compared to stamped steels with zinc coating with a reduced coefficient of friction and improving the anti-sticking properties of the tool surface.

Repairing the cracks network of hard chromium electroplated layers using plasma nitriding technique

The use of hard chromium electroplated coatings for industrial and decorative applications is widespread. However, there seem to be some defects like the existence of an extensive micro-cracks network that restrict their applications. They affect corrosion resistance due to formation of direct routes to the substrate through which corrosive agents could reach the main metal. Plasma nitriding process is proved an effective technique to overcome such problems. The objective of this study is to investigate the effect of plasma nitriding parameters namely, time and temperature, on the closure of the cracks. Samples of a hard chromium electroplated hot work tool steel were heat-treated via conventional plasma nitriding (CPN) and active screen plasma nitriding processes (ASPN) at 500 and 550 °C for 5 and 10 h, and at 550 and 600 °C for 10 and 15 h, respectively. The morphology and microstructure of the samples were characterized by the scanning electron microscopy (SEM) imaging. The coating phases were determined by the X-ray diffraction (XRD) method. The corrosion properties of samples were evaluated using anodic polarization tests in a 3.5 wt% NaCl solution at 25 °C. The results showed that both techniques filled up the cracks. However, the closure mechanisms were different. In CPN method, the cracks were disappeared due to the transformation of chromium to its nitrides, which occur with volume expansion. It is worth noting that this phenomenon occurs at lower temperatures and shorter times compared to ASPN method. In ASPN method, the iron nitrides detached from active screen were deposited inside the cracks to fill them up. Moreover, it was found that the corrosion resistances of the samples modified by the CPN process were superior to the ASPN samples.

The Effect of Plasma Nitriding Parameters on the Thickness of Nitrided Layers

This paper is aimed at chemical-heat treatment of a selected material. The plasma nitriding layers were applied on the 41CrAlMo7-10 steel. The influence of plasma nitriding parameters on the thickness and microhardness of nitrided layers were investigated. Plasma nitriding was performed at 500°C with a mixture atmosphere of H2 and N2 in the plasma nitriding equipment. The pressure of plasma nitriding process was determined to be 280 Pa. The period of the plasma nitriding process was changeable from 5 to 30 hours. The microstructure and mechanical properties of the nitrided layers were studied by using GDOES spectrometry, optical microscopy, and hardness testing. The depths of the plasma nitriding layers were also estimated using cross-sectional microhardness profiles. Microhardness and surface hardness of mentioned samples were significantly increased. The measurements have shown that the period of plasma nitriding process has a significant influence on the depth of nitriding.

Plasma Ion Nitriding of Low Carbon Stainless Maraging Steel

Low carbon stainless maraging steel (0.03%C-12%Cr-10Ni-0.6Mo-0.2Ti) is being used widely for various components of the aerospace engines. To improve the wear resistance of the steel various surface hardening processes are being utilized to improve the surface hardness above 900HV. In this present research, plasma nitriding was carried out at two different temperatures of 450 °C and 475 °C for the holding duration of 10 hrs. Temperature of the nitrding process was ensured below the ageing temperature (500 °C) of the steel to avoid lowering of mechanical properties. Effect of plasma nitriding parameters on the surface hardness, case depth, microstructure and phases present in the nitrided layer were investigated in detail using microhardness analysis across the nitrided layer, X-ray diffraction (XRD), optical microscopy and scanning electron microscopy (SEM). It was observed that increase in nitriding temperature increased the surface hardness and case depth. In addition, the presence of Fe3N and Fe4N phases in the nitrided layer were observed using X-ray diffraction technique.

The effect of plasma nitriding on the fatigue behavior of DIN 1.2210 cold work tool steel

Plasma nitriding is an important thermo-chemical surface treatment which is widely used in order to enhance the surface hardness, fatigue strength and wear and corrosion resistance of steels. In this research, the effects of plasma nitriding parameters including temperature and time on the microstructure and fatigue strength of quenched and tempered DIN 1.2210 cold work tool steel were investigated. The microstructures of base material and nitrided layer were examined in details by optical microscopy and X-ray diffraction (XRD) analysis. Micro-hardness measurements were used to determine surface hardness and case depth. Fatigue tests were performed using a rotating bending machine. The results indicated that the plasma nitriding process led to a considerable increase in the micro-hardness and fatigue strength values. Furthermore, the maximum fatigue strength was attained after plasma nitriding at 550°C for 6h, which increased the fatigue life of the specimens by about 67%. It was also found that the dominant fatigue crack initiation mechanism in the plasma nitrided specimens was subsurface ‘fish eye’ type crack formation originated from internal nonmetallic inclusions.

Effects of DC plasma nitriding parameters on microstructure and properties of 304L stainless steel

A wear-resistant nitrided layer was formed on a 304L austenitic stainless steel substrate by DC plasma nitriding. Effects of DC plasma nitriding parameters on the structural phases, micro-hardness and dry-sliding wear behavior of the nitrided layer were investigated by optical microscopy, X-ray diffraction, scanning electron microscopy, micro-hardness testing and ring-on-block wear testing. The results show that the highest surface hardness over a case depth of about 10 µm is obtained after nitriding at 460 °C. XRD indicated a single expanded austenite phase and a single CrN nitride phase were formed at 350 °C and 480 °C, respectively. In addition, the S-phase layers formed on the samples provided the best dry-sliding wear resistance under the ring-on-block contact configuration test.

An in-situ study of plasma nitriding

Direct in-situ observation of phase generation and growth during heat treatment cycles gives information independent e.g. of effects resulting from cooling and atmospheric changes of properties. In this investigation time resolved in-situ X-ray diffraction (XRD) analysis of growing nitride layers during plasma nitriding was conducted to gain experimental data of growing compound layers for different plasma nitriding parameters. With two gas mixtures of 5% N 2–95% H 2 and 25% N 2–75% H 2. plasma nitriding of an AISI 1045 steel was performed in the temperature range of 450 °C < T < 560 °C. The in-situ XRD-observation consisted of series of 50 to 60 single runs of phase analysis during a 3-h plasma nitriding treatment. Nitriding with the formation of nitride phases starts at different times, depending on the nitriding temperature and the gas composition in the plasma for the given plasma parameters pressure, voltage and current density. The higher the nitriding temperature and the higher the nitrogen content in the process gas the shorter is the time for the first detection of the γ′-Fe 4N-phase. Single phase γ′nitride layers were detected for the 5% N 2–95% H 2 gas mixture in a temperature range 450 °C < T < 560 °C. For the highest temperatures 540 °C and 560 °C and the gas mixture 25% N 2–75% H 2 the ε-Fe 2–3N phase occurred later in the plasma nitriding process. Assuming that nitride layers in plasma nitriding also grow by nucleation of small γ′ particles up to a complete layer, the experimental data fitted in a reasonable way in plots calculated for the incubation time of the γ′-phase during gas nitriding.

Determining Nitriding Parameters with Neural Networks

Abstract The choice of correct plasma nitriding parameters is usually experience-based. There are no successful mathematical models for the nitriding process simulation. An attempt has been made to accurately determine required nitriding time for the specified effective nitriding layer thickness, sum of weight contents of nitride forming elements in steel, and nitriding temperature. Two methods were used to solve this problem: the statistical multiple regression and the artificial neural network. It is not possible to find a regression model that would relate the three variables to nitriding time, whereas good results were achieved with neural networks. The second problem that was investigated was the determination of post-nitriding surface hardness on the basis of three known parameters: nitriding time and temperature, and the sum of weight contents of nitride forming elements in steel. Again, a general regression model was not found, and the neural networks produced very good results.

Tribological behaviour of plasma nitrided and plasma sulfonitrided cold work steels

Many different nitriding processes have been used for reducing the wear of iron based and non-iron based materials. In the present work, the efficiency of plasma nitriding of cold work steels for reducing wear was investigated. Ball on disc tests were conducted at room temperature and200°C using austenitic stainless steel balls and different nitrided cold work steel discs. The thickness of both compound and diffusion layer and the composition of the compound layer were varied by changing the plasma nitriding parameters. Wear tracks on the discs and balls were characterisedusing both SEM and optical profiling. The results show that a thinner nitrided layer reduces wear more efficiently. Higher carbide content seems to be advantageous because the nitrided layer is mechanically better supported.

Inductively coupled plasma nitriding of aluminium

Substrates of aluminium alloy 2011 were plasma nitrided using an inductively coupled plasma source. The plasma nitriding parameters of temperature, length of nitriding and negative dc bias of the substrates were varied in order to optimise the plasma nitriding process. Substrates were characterised by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). All nitriding was carried out at a rf power level of 100 W and pressure of 6.5×10 −3 Torr N 2 . AlN was detected by XPS on all plasma nitrided Al substrates but the relative contribution of AlN to the total Al photoelectron signal was not significant (<15%) for Al substrates treated at low temperatures (50 and 450 °C) and low negative dc bias (100 and 150 V, respectively). AlN was not detected by XRD in these instances. Significant formation of AlN was observed both by XPS and XRD after nitriding for 180 min at a temperature of 575 °C whilst the substrate was biased with a negative dc voltage of 400 V. AlN formed at 575 °C both with and without prior Ar sputtering of the naturally occurring aluminium oxide over layer giving rise to an AlN contribution to the total Al photoelectron signal of 49 and 21%, respectively. XRD analysis confirmed the presence of a surface polycrystalline AlN layer. Both AlN and Al 2 O 3 were also observed by XPS on the surface of the nitrided Al substrates. SEM revealed a nodular morphology of the nitrided surfaces which were black in colour and exhibited a 2–3 μm thick surface layer. Nitriding of an Al substrate at 485 °C with dc bias of −400 V gave rise to a 35% AlN contribution to the total Al photoelectron signal. However, no AlN XRD pattern was observed. This indicates formation of a thin AlN layer only.

Microstructure and residual stresses of a plasma-nitrided M2 tool steel

Abstract Nitriding leads to improved tribological and corrosive properties of iron-alloy components. In order to study the effect of plasma-nitriding parameters on the structure of the compound layer and diffusion zone, a systematic variation of process parameters, temperature and process gas atmosphere has been carried out. Metallographic inspection, X-ray diffraction and glow discharge optical spectroscopy analysis were used in the investigation. The results revealed that, depending on the amount of nitrogen in the gas atmosphere, nitrided layers with and without a compound layer can be generated in the surface of M2 tool steel for temperatures ranging from 350 to 500°C. For plasma nitriding in 5 vol.% nitrogen and 95 vol.% hydrogen, no compact compound layer was formed. The gas mixture of 76 vol.% nitrogen resulted in compound layer formation for all temperatures from 350 to 500°C. X-ray phase analysis indicated an almost 100% ϵ-(carbo)nitride phase, but the existence of the γ′-(carbo)nitride could not be excluded completely from the X-ray phase diagrams. After corrections had been made according to the nitrogen gradient, high compressive surface residual stresses were measured in the diffusion zone and were found to increase with temperature. After a qualitative correction for chemical composition gradients, high tensile residual stresses were found, probably existing in the ϵ-(carbo)nitride phase for the investigated plasma-nitrided tool-steel samples.

An Assessment Of The Effect Of Plasma NitridingAnd Nitrocarburizing Parameters On TheCorrosion Resistance Of Sintered Steel Using TheResponse Surface Method

The Response Surface Method is an effective means of addressing the combined effect of plasma nitriding parameters on the corrosion resistance of materials. In this work, sintered steel was nitrided under different atmospheres: 75%N: 25%H2, and 25%N: 75%Hi. In addition, a series of samples was also nitrocarburized by adding CH4 to the nitrogen-enriched atmosphere. The thickness and composition of the resulting compound layers were determined, along with the resulting microhardness profiles. Finally, the corrosion resistance of the plasma-treated materials was evaluated by potentiodynamic polarization technique. The results indicated that the addition of CH^ to the plasma atmosphere increased the hardening depth and improved the corrosion rate of the resulting material.