Fisnik Aliaj | University of Prishtina (original) (raw)

Papers by Fisnik Aliaj

Acta Physica Polonica A

This work is an experimental study of the hardness curve in the zone of diffusion for the gas nit... more This work is an experimental study of the hardness curve in the zone of diffusion for the gas nitriding process of 31CrMoV9 steel. 12 samples were subjected to gas nitriding at three different temperatures-510 • C, 550 • C, and 590 • C-and for each temperature four different nitriding times were used. Hardness was measured with an automatic microhardness tester PCE from LECO with a load of HV0.1 (0.9807N), and the distance between the points was 50 µm. It was found that the hardness of the diffusion layer changed from 602 HV to 787 HV. The maximum surface hardness was found at 510 • C after nitriding for 16 h. Depending on the process parameters, the depth of the diffusion layer ranged from 270 µm to 700 µm. From the results we can draw conclusions for the gradient curve of nitriding parameters, and from each curve we can find the depth of the diffusion of nitrogen in steel.

IJCT Vol.26(4) [July 2019], Jul 1, 2019

This is a numerical and experimental study of the hardness curves in the precipitation layer of g... more This is a numerical and experimental study of the hardness curves in the precipitation layer of gaseous nitrided 31CrMoV9 alloy steel. Hardness has been measured with an automatic micro-hardness meter according to the Vickers method. It is known that gas nitriding as a diffusion process can be described by the differential equation known as Fick's second law. This equation is solved with the Finite Element (FE) method. Modeling is based on the Orowan strengthening theory and the classic Johnson-Mehl-Avrami theory of precipitation. The model is constructed in the ANSYS application in the temperature field and experimental results are compared with theory (the model). The results prove that diffusion processes like nitriding can be modeled with FE methods.

International Journal of Computational and Experimental Science and Engineering, 2021

This study is concerned with experimental curves of: hardness, residual stress and concentration ... more This study is concerned with experimental curves of: hardness, residual stress and concentration of nitrogen at the precipitation layer at alloy steels after gas nitriding. The purpose of this treatment is that through experimental curves to identify the relationship and causality between hardness, on one side, and on the other, residual stress respectively concentration of nitrogen. Comparing the shape and slope of these curves we can conclude that, concentration of diffused nitrogen on the steel lattice, respectively ferrite, is a cause of increased hardness at the precipitation layer. More to the point, as a result of nitrogen diffusion, residual stress emerge which cause increase of hardness. The intensity and slope of the curves of hardness depends on the intensity and slope of the nitrogen concentration respectively residual stress.

Emerging Materials Research, 2022

This research aims to determine the depth of diffusion of nitrogen in steel 16MnCr5 after gas nit... more This research aims to determine the depth of diffusion of nitrogen in steel 16MnCr5 after gas nitriding. Nitriding was performed in the ammonia atmosphere at three temperatures (510, 550 and 590°C), with four different durations for each temperature. The research techniques were metallographic and electron probe micro-analysis (EPMA). According to the first method, with the optical microscope Neophot 30 of the firm Carl Zeiss Jena, the surfaces of all samples were observed. The nitriding layers were photographed with the help of a microscope, from which the depths of nitrogen diffusion were determined. The hardness-depth profiles of nitride specimens were determined with a Vickers automatic micro-hardness tester from LECO, and the distance between two consecutive points was 50 μm. The depth of nitrogen diffusion into the nitride samples was determined from the hardness curves. The nitrogen concentration-depth profiles of the nitrided specimens were determined with EPMA using a Joel ...

International Journal of Computational and Experimental Science and Engineering, 2021

Non-evaporable getter (NEG) materials have become an integral part of many ultrahigh vacuum envir... more Non-evaporable getter (NEG) materials have become an integral part of many ultrahigh vacuum environments mainly due to their unique surface properties which are able to achieving extreme-high vacuum conditions of the order of 10 −12 mbar and lower. NEG materials have to be " activated " after exposure to atmospheric gases. Activation is performed by heating the getter to appropriate temperature in order to remove the adsorbed gas molecules/ atoms (mainly oxygen and carbon) from the getter surface to get atomically clean metal surface of getter alloy. Main mechanism of removal of oxygen and carbon is diffusion from the surface layer into the bulk. The elements in getter alloy shall have high diffusivity and high solubility for oxygen and carbon. Diffusion of oxygen gas has been studied for pure metals, but for getter alloys there is almost no data available. At low temperature the diffusion length may be only of the order of few nm so we used surface sensitive analytical te...

Acta Physica Polonica A, 2020

This work presents studies of naturally enhanced ion acoustic lines and the correlation they have... more This work presents studies of naturally enhanced ion acoustic lines and the correlation they have with the electron temperature fluctuations on the eve and after the NEIAL events. The methodology used in this work is based on the analysis of European Incoherent Scatter Scientific Association raw data, archived at Rutherford-Appleton Laboratory (Harwell Oxford Campus) in the United Kingdom. The EISCAT Svalbard radar raw data were analyzed using two specialized programs: the Real Time Graph and the Grand Unified Incoherent Scatter Data Analysis Program, version 8.6. Our findings suggest a strong correlation between the NEIALs phenomenon and plasma parameter fluctuations such as the electron temperature in the Earth ionosphere. Our findings show that the plasma electron temperature progressively increases before the event, and progressively decreases after the event.

Emerging Materials Research, 2020

This paper presents a possibility for the numerical calculation of the profile of nitrogen (N) co... more This paper presents a possibility for the numerical calculation of the profile of nitrogen (N) concentration in 31CrMoV9 steel after gas nitriding. Samples subjected to gas nitriding at three diffe...

International Journal of Thermophysics, 2020

Experimental densities at (293.15, 298.15, 303.15, 308.15, and 313.15) K and refractive indices a... more Experimental densities at (293.15, 298.15, 303.15, 308.15, and 313.15) K and refractive indices at 298.15 K are reported for the binary liquid mixtures of ethanol with benzene and pyridine over the entire range of compositions and atmospheric pressure. From these experimental data, the excess molar volumes V E and deviations in molar refractivity Δ R were derived and fitted by the Redlich–Kister polynomial to determine the adjustable fitting parameters and the standard deviations. The number of adjustable parameters to be included in a Redlich–Kister polynomial for fitting the derived properties was optimized with the F -test. V E values are found to be negative over the entire composition range in ethanol + pyridine mixtures, without considerable changes over the temperature range studied. In the ethanol + benzene mixtures, the V E results show an S-shaped composition dependence, and the temperature contribution was found to be very important. The variation of V E with composition and temperature has been interpreted in terms of molecular interactions between the components of the mixture and structural effects. Δ R values are found to be negative for both mixtures with a minimum located between 0.45 and 0.5 volume fractions of ethanol. Furthermore, several theoretical and empirical mixing rules were applied to predict refractive indices of mixtures in order to test their validity for the present systems.

Acta Physica Polonica A, 2016

The law of growth of nitrided layers produced by gaseous nitriding of 31CrMoV9 alloy steel at dif... more The law of growth of nitrided layers produced by gaseous nitriding of 31CrMoV9 alloy steel at different process parameters is described. 31CrMoV9 steel specimens were subjected to nitriding process in ammonia gas at three different temperatures: 510, 550 and 590 • C, and for each temperature four different nitriding times were used. This way twelve specimens were produced. Nitrided specimens were investigated with optical microscopy, electron probe micro-analysis and x-ray diffraction. The nitrogen depth concentration profiles, deduced from electron probe micro-analysis, in conjunction with results of optical microscopy, were used to determine the thickness of the nitrided layers, i.e. the diffusion depth of nitrogen. From the dependence of the nitrided layer thickness on process parameters (temperature and time) it was possible to deduce the law that governs the growth of the nitrided layer for 31CrMoV9 alloy steel. Through this law, then, it is possible to predetermine the layer thickness for every real process parameter in nitriding of 31CrMoV9 steel, which is very important for technological applications.

Proceedings of The 4th Global Virtual Conference, 2016

Proceedings of The 4th Global Virtual Conference, 2016

AIP Conference Proceedings, 2016

Densities, ρ, and refractive indices, nD, of the ternary liquid mixture benzene (1) + ethanol (2)... more Densities, ρ, and refractive indices, nD, of the ternary liquid mixture benzene (1) + ethanol (2) + hexane (3), have been measured at temperature of 293.15 K and atmospheric pressure. The changes in the refractive indices have also been measured with temperature in the range T = (293.15 to 313.15) K. The mole fraction of the second component (ethanol) was set to 0.4, while the mole fractions of the remaining components were changed so as to cover the whole composition range. Excess molar volumes, VE, and deviations in the refractive indices from the volume fraction average, ΔnD, have been calculated for each investigated temperature and compared with others in literature. In all cases, VE was positive and ΔnD were negative and both showed deviations from ideality. Furthermore, refractive indices of the ternary liquid mixture were predicted by using several theoretical and empirical mixing rules, and the obtained results were discussed in terms of average percentage deviations.

Finite element method (FEM) through ANSYS software package was used to numerically model various ... more Finite element method (FEM) through ANSYS software package was used to numerically model various metallic beams simply supported and subjected to central concentrated static load. The results of the model were compared with experimental investigations and good agreement was found. The material data of the investigated metal beams, like density, modulus of elasticity and Poisson’s ratio, necessary to perform the modeling were taken from literature. From the least square fitting on the maximum deflection of the beam as a function of the applied load, obtained experimentally, and given the geometric data of the beams, it was possible to evaluate the modulus of elasticity of the metals. Moduli of elasticity obtained in this way were within 5% of the values found in literature. Additional experiments based on impulse excitation technique, as per ASTM standard E1876/C1259, were performed to further check the moduli of elasticity of the investigated metal beams.

X-ray diffraction depth profiling using successive material removal was used to characterize the ... more X-ray diffraction depth profiling using successive material removal was used to characterize the nitrided layers produced by gaseous nitriding on 31CrMoV9 steel. The variation of phase composition and residual stresses has been determined in this way as a function of depth. Phase analysis was performed using a Siefert-FPM diffractometer with Co-K radiation operated in Bragg-Brentano geometry. The diffraction patterns were taken by scanning between 2 values of 35 – 105o in steps of 0.05o and counting time of 45s per step. Residual stress measurements were carried out applying the sin2-method using a Huber diffractometer equipped with an Eulerian cradle and Cr-K target. The -Fe (211) reflection was scanned in steps of 0.05o with a counting time of 20s per step. Experimental results reveal the presence of CrN and cementite phases in the precipitation layer and their depth variation. The residual stresses vary with depth and zones of compressive and tensile stresses are distinguished.

The Non-evaporable getter (NEG) materials have become an integral part of many ultrahigh vacuum e... more The Non-evaporable getter (NEG) materials have become an integral part of many ultrahigh vacuum environments mainly due to their unique surface properties which are able to achieving extreme high vacuum conditions of the order of 10-12 mbar and lower. NEG materials have to be “activated” after exposure to atmospheric gases. Activation is performed by heating the getter to appropriate temperature in order to remove the adsorbed gas molecules/ atoms (mainly oxygen and carbon) from the getter surface to get atomically clean metal surface of getter alloy. Main mechanism of removal of oxygen and carbon is diffusion from the surface layer into the bulk. The elements in getter alloy shall have high diffusivity and high solubility for oxygen and carbon. Diffusion of oxygen gas has been studied for pure metals, but for getter alloys there is almost no data available. At low temperature the diffusion length may be only of the order of few nm so we used surface sensitive analytical techniques ...

In this contribution, the residual stresses in the precipitation layer of selected alloy steels a... more In this contribution, the residual stresses in the precipitation layer of selected alloy steels after gaseous nitriding process was investigated. Gaseous nitriding was performed at different temperatures and times, which resulted in different diffusion depth for atomic nitrogen. As a result of diffusion of atomic nitrogen, the crystal lattice of steel deforms, and as a consequence residual stresses in tension and compression appear. These residual stresses affect the strength increase and improvement of other surface properties of steels. Investigation of composition, cross-sectional morphology, hardness and residual stress of nitrided alloy steels (16MnCr5 and 31CrMoV9) was carried out using Electron Probe Micro Analysis (EPMA), Light Optical Microscopy (LOM), micro-hardness according to Vickers and X-ray Diffraction (XRD) techniques. The results show that intensity of stresses and hardness increase depend on the nitrogen diffusion depth, that is on nitriding process parameters.

Gaseous nitriding is a thermochemical surface treatment process, usually performed at temperature... more Gaseous nitriding is a thermochemical surface treatment process, usually performed at temperatures between 500 and 590 oC, which leads to improvements in surface properties of steels such as resistance to wear, fatigue and corrosion. In this contribution the nitrogen depth-concentration profile in precipitation layer of gaseous nitrided 17CrMoV10 alloy steel was investigated both experimentally and numerically. Experimental nitrogen concentration profiles were deduced from EPMA (Electron Probe Micro Analysis) measurements by using a Joel JXA-8900 RL Electron Probe Microanalyzer (U = 20 kV, I = 40 nA). Finite element method (FEM) through ANSYS software package was used to numerically model the nitrogen concentration profiles. The experimental results were compared with the results obtained from FE model, and good agreement was found that is also an indication that our approach in modeling the nitrogen concentration profile is valid. The validity of the proposed model makes it a valua...

Acta Physica Polonica A

This work is an experimental study of the hardness curve in the zone of diffusion for the gas nit... more This work is an experimental study of the hardness curve in the zone of diffusion for the gas nitriding process of 31CrMoV9 steel. 12 samples were subjected to gas nitriding at three different temperatures-510 • C, 550 • C, and 590 • C-and for each temperature four different nitriding times were used. Hardness was measured with an automatic microhardness tester PCE from LECO with a load of HV0.1 (0.9807N), and the distance between the points was 50 µm. It was found that the hardness of the diffusion layer changed from 602 HV to 787 HV. The maximum surface hardness was found at 510 • C after nitriding for 16 h. Depending on the process parameters, the depth of the diffusion layer ranged from 270 µm to 700 µm. From the results we can draw conclusions for the gradient curve of nitriding parameters, and from each curve we can find the depth of the diffusion of nitrogen in steel.

IJCT Vol.26(4) [July 2019], Jul 1, 2019

This is a numerical and experimental study of the hardness curves in the precipitation layer of g... more This is a numerical and experimental study of the hardness curves in the precipitation layer of gaseous nitrided 31CrMoV9 alloy steel. Hardness has been measured with an automatic micro-hardness meter according to the Vickers method. It is known that gas nitriding as a diffusion process can be described by the differential equation known as Fick's second law. This equation is solved with the Finite Element (FE) method. Modeling is based on the Orowan strengthening theory and the classic Johnson-Mehl-Avrami theory of precipitation. The model is constructed in the ANSYS application in the temperature field and experimental results are compared with theory (the model). The results prove that diffusion processes like nitriding can be modeled with FE methods.

International Journal of Computational and Experimental Science and Engineering, 2021

This study is concerned with experimental curves of: hardness, residual stress and concentration ... more This study is concerned with experimental curves of: hardness, residual stress and concentration of nitrogen at the precipitation layer at alloy steels after gas nitriding. The purpose of this treatment is that through experimental curves to identify the relationship and causality between hardness, on one side, and on the other, residual stress respectively concentration of nitrogen. Comparing the shape and slope of these curves we can conclude that, concentration of diffused nitrogen on the steel lattice, respectively ferrite, is a cause of increased hardness at the precipitation layer. More to the point, as a result of nitrogen diffusion, residual stress emerge which cause increase of hardness. The intensity and slope of the curves of hardness depends on the intensity and slope of the nitrogen concentration respectively residual stress.

Emerging Materials Research, 2022

This research aims to determine the depth of diffusion of nitrogen in steel 16MnCr5 after gas nit... more This research aims to determine the depth of diffusion of nitrogen in steel 16MnCr5 after gas nitriding. Nitriding was performed in the ammonia atmosphere at three temperatures (510, 550 and 590°C), with four different durations for each temperature. The research techniques were metallographic and electron probe micro-analysis (EPMA). According to the first method, with the optical microscope Neophot 30 of the firm Carl Zeiss Jena, the surfaces of all samples were observed. The nitriding layers were photographed with the help of a microscope, from which the depths of nitrogen diffusion were determined. The hardness-depth profiles of nitride specimens were determined with a Vickers automatic micro-hardness tester from LECO, and the distance between two consecutive points was 50 μm. The depth of nitrogen diffusion into the nitride samples was determined from the hardness curves. The nitrogen concentration-depth profiles of the nitrided specimens were determined with EPMA using a Joel ...

International Journal of Computational and Experimental Science and Engineering, 2021

Non-evaporable getter (NEG) materials have become an integral part of many ultrahigh vacuum envir... more Non-evaporable getter (NEG) materials have become an integral part of many ultrahigh vacuum environments mainly due to their unique surface properties which are able to achieving extreme-high vacuum conditions of the order of 10 −12 mbar and lower. NEG materials have to be " activated " after exposure to atmospheric gases. Activation is performed by heating the getter to appropriate temperature in order to remove the adsorbed gas molecules/ atoms (mainly oxygen and carbon) from the getter surface to get atomically clean metal surface of getter alloy. Main mechanism of removal of oxygen and carbon is diffusion from the surface layer into the bulk. The elements in getter alloy shall have high diffusivity and high solubility for oxygen and carbon. Diffusion of oxygen gas has been studied for pure metals, but for getter alloys there is almost no data available. At low temperature the diffusion length may be only of the order of few nm so we used surface sensitive analytical te...

Acta Physica Polonica A, 2020

This work presents studies of naturally enhanced ion acoustic lines and the correlation they have... more This work presents studies of naturally enhanced ion acoustic lines and the correlation they have with the electron temperature fluctuations on the eve and after the NEIAL events. The methodology used in this work is based on the analysis of European Incoherent Scatter Scientific Association raw data, archived at Rutherford-Appleton Laboratory (Harwell Oxford Campus) in the United Kingdom. The EISCAT Svalbard radar raw data were analyzed using two specialized programs: the Real Time Graph and the Grand Unified Incoherent Scatter Data Analysis Program, version 8.6. Our findings suggest a strong correlation between the NEIALs phenomenon and plasma parameter fluctuations such as the electron temperature in the Earth ionosphere. Our findings show that the plasma electron temperature progressively increases before the event, and progressively decreases after the event.

Emerging Materials Research, 2020

This paper presents a possibility for the numerical calculation of the profile of nitrogen (N) co... more This paper presents a possibility for the numerical calculation of the profile of nitrogen (N) concentration in 31CrMoV9 steel after gas nitriding. Samples subjected to gas nitriding at three diffe...

International Journal of Thermophysics, 2020

Experimental densities at (293.15, 298.15, 303.15, 308.15, and 313.15) K and refractive indices a... more Experimental densities at (293.15, 298.15, 303.15, 308.15, and 313.15) K and refractive indices at 298.15 K are reported for the binary liquid mixtures of ethanol with benzene and pyridine over the entire range of compositions and atmospheric pressure. From these experimental data, the excess molar volumes V E and deviations in molar refractivity Δ R were derived and fitted by the Redlich–Kister polynomial to determine the adjustable fitting parameters and the standard deviations. The number of adjustable parameters to be included in a Redlich–Kister polynomial for fitting the derived properties was optimized with the F -test. V E values are found to be negative over the entire composition range in ethanol + pyridine mixtures, without considerable changes over the temperature range studied. In the ethanol + benzene mixtures, the V E results show an S-shaped composition dependence, and the temperature contribution was found to be very important. The variation of V E with composition and temperature has been interpreted in terms of molecular interactions between the components of the mixture and structural effects. Δ R values are found to be negative for both mixtures with a minimum located between 0.45 and 0.5 volume fractions of ethanol. Furthermore, several theoretical and empirical mixing rules were applied to predict refractive indices of mixtures in order to test their validity for the present systems.

Acta Physica Polonica A, 2016

The law of growth of nitrided layers produced by gaseous nitriding of 31CrMoV9 alloy steel at dif... more The law of growth of nitrided layers produced by gaseous nitriding of 31CrMoV9 alloy steel at different process parameters is described. 31CrMoV9 steel specimens were subjected to nitriding process in ammonia gas at three different temperatures: 510, 550 and 590 • C, and for each temperature four different nitriding times were used. This way twelve specimens were produced. Nitrided specimens were investigated with optical microscopy, electron probe micro-analysis and x-ray diffraction. The nitrogen depth concentration profiles, deduced from electron probe micro-analysis, in conjunction with results of optical microscopy, were used to determine the thickness of the nitrided layers, i.e. the diffusion depth of nitrogen. From the dependence of the nitrided layer thickness on process parameters (temperature and time) it was possible to deduce the law that governs the growth of the nitrided layer for 31CrMoV9 alloy steel. Through this law, then, it is possible to predetermine the layer thickness for every real process parameter in nitriding of 31CrMoV9 steel, which is very important for technological applications.

Proceedings of The 4th Global Virtual Conference, 2016

Proceedings of The 4th Global Virtual Conference, 2016

AIP Conference Proceedings, 2016

Densities, ρ, and refractive indices, nD, of the ternary liquid mixture benzene (1) + ethanol (2)... more Densities, ρ, and refractive indices, nD, of the ternary liquid mixture benzene (1) + ethanol (2) + hexane (3), have been measured at temperature of 293.15 K and atmospheric pressure. The changes in the refractive indices have also been measured with temperature in the range T = (293.15 to 313.15) K. The mole fraction of the second component (ethanol) was set to 0.4, while the mole fractions of the remaining components were changed so as to cover the whole composition range. Excess molar volumes, VE, and deviations in the refractive indices from the volume fraction average, ΔnD, have been calculated for each investigated temperature and compared with others in literature. In all cases, VE was positive and ΔnD were negative and both showed deviations from ideality. Furthermore, refractive indices of the ternary liquid mixture were predicted by using several theoretical and empirical mixing rules, and the obtained results were discussed in terms of average percentage deviations.

Finite element method (FEM) through ANSYS software package was used to numerically model various ... more Finite element method (FEM) through ANSYS software package was used to numerically model various metallic beams simply supported and subjected to central concentrated static load. The results of the model were compared with experimental investigations and good agreement was found. The material data of the investigated metal beams, like density, modulus of elasticity and Poisson’s ratio, necessary to perform the modeling were taken from literature. From the least square fitting on the maximum deflection of the beam as a function of the applied load, obtained experimentally, and given the geometric data of the beams, it was possible to evaluate the modulus of elasticity of the metals. Moduli of elasticity obtained in this way were within 5% of the values found in literature. Additional experiments based on impulse excitation technique, as per ASTM standard E1876/C1259, were performed to further check the moduli of elasticity of the investigated metal beams.

X-ray diffraction depth profiling using successive material removal was used to characterize the ... more X-ray diffraction depth profiling using successive material removal was used to characterize the nitrided layers produced by gaseous nitriding on 31CrMoV9 steel. The variation of phase composition and residual stresses has been determined in this way as a function of depth. Phase analysis was performed using a Siefert-FPM diffractometer with Co-K radiation operated in Bragg-Brentano geometry. The diffraction patterns were taken by scanning between 2 values of 35 – 105o in steps of 0.05o and counting time of 45s per step. Residual stress measurements were carried out applying the sin2-method using a Huber diffractometer equipped with an Eulerian cradle and Cr-K target. The -Fe (211) reflection was scanned in steps of 0.05o with a counting time of 20s per step. Experimental results reveal the presence of CrN and cementite phases in the precipitation layer and their depth variation. The residual stresses vary with depth and zones of compressive and tensile stresses are distinguished.

The Non-evaporable getter (NEG) materials have become an integral part of many ultrahigh vacuum e... more The Non-evaporable getter (NEG) materials have become an integral part of many ultrahigh vacuum environments mainly due to their unique surface properties which are able to achieving extreme high vacuum conditions of the order of 10-12 mbar and lower. NEG materials have to be “activated” after exposure to atmospheric gases. Activation is performed by heating the getter to appropriate temperature in order to remove the adsorbed gas molecules/ atoms (mainly oxygen and carbon) from the getter surface to get atomically clean metal surface of getter alloy. Main mechanism of removal of oxygen and carbon is diffusion from the surface layer into the bulk. The elements in getter alloy shall have high diffusivity and high solubility for oxygen and carbon. Diffusion of oxygen gas has been studied for pure metals, but for getter alloys there is almost no data available. At low temperature the diffusion length may be only of the order of few nm so we used surface sensitive analytical techniques ...

In this contribution, the residual stresses in the precipitation layer of selected alloy steels a... more In this contribution, the residual stresses in the precipitation layer of selected alloy steels after gaseous nitriding process was investigated. Gaseous nitriding was performed at different temperatures and times, which resulted in different diffusion depth for atomic nitrogen. As a result of diffusion of atomic nitrogen, the crystal lattice of steel deforms, and as a consequence residual stresses in tension and compression appear. These residual stresses affect the strength increase and improvement of other surface properties of steels. Investigation of composition, cross-sectional morphology, hardness and residual stress of nitrided alloy steels (16MnCr5 and 31CrMoV9) was carried out using Electron Probe Micro Analysis (EPMA), Light Optical Microscopy (LOM), micro-hardness according to Vickers and X-ray Diffraction (XRD) techniques. The results show that intensity of stresses and hardness increase depend on the nitrogen diffusion depth, that is on nitriding process parameters.

Gaseous nitriding is a thermochemical surface treatment process, usually performed at temperature... more Gaseous nitriding is a thermochemical surface treatment process, usually performed at temperatures between 500 and 590 oC, which leads to improvements in surface properties of steels such as resistance to wear, fatigue and corrosion. In this contribution the nitrogen depth-concentration profile in precipitation layer of gaseous nitrided 17CrMoV10 alloy steel was investigated both experimentally and numerically. Experimental nitrogen concentration profiles were deduced from EPMA (Electron Probe Micro Analysis) measurements by using a Joel JXA-8900 RL Electron Probe Microanalyzer (U = 20 kV, I = 40 nA). Finite element method (FEM) through ANSYS software package was used to numerically model the nitrogen concentration profiles. The experimental results were compared with the results obtained from FE model, and good agreement was found that is also an indication that our approach in modeling the nitrogen concentration profile is valid. The validity of the proposed model makes it a valua...