D. Manova - Academia.edu (original) (raw)

Papers by D. Manova

Surface and Coatings Technology, 2014

ABSTRACT The formation of expanded austenite after nitrogen insertion into austenitic stainless s... more ABSTRACT The formation of expanded austenite after nitrogen insertion into austenitic stainless steel, CoCr or Ni base alloys is characterised by an unusually high nitrogen content in solid solution representing a diffusion layer. However, the process is still not completely understood. Using in situ X-ray diffraction (XRD) experiments and additional data from SEM, the phase formation and diffusion after low energy nitrogen ion implantation into commercial Ni80Cr20 (Nichrome) are investigated in the temperature range from 350 to 500 °C. A compound layer consisting of a phase similar to fct Ni4N is formed on the surface, most likely with a composition of (Ni,Cr)4N, followed by a diffusion zone extending about 1 μm into the material. For increasing temperature, the total nitrogen uptake is decreasing. The time evolution shows that a saturation is reached earlier for higher temperatures whereas no saturation has been found for 375 °C and 90 min. A competition exists between nitrogen loss at the surface and nitrogen supply by the ion beam. This loss process is thermally activated and depends on the surface orientation. Additionally, at 500 °C some CrN precipitates are found.

2000 International Conference on Ion Implantation Technology Proceedings. Ion Implantation Technology - 2000 (Cat. No.00EX432), 2000

ABSTRACT In this report the formation of textured and dense TiN films on Si by MePIID at room tem... more ABSTRACT In this report the formation of textured and dense TiN films on Si by MePIID at room temperature is investigated. The high voltage pulses with duty cycles of 9% were varied between 0 and 10 kV. The growth rates of a few nanometers per second, depending on the arc current, were calculated using results from elastic recoil detection analysis (ERDA). Using resonant Rutherford backscattering spectroscopy (RRBS), contamination levels of less than 0.5% oxygen were determined. With X-ray diffraction (XRD) and pole figure measurements a highly oriented TiN phase was observed for all bias voltages. The (200) axis is normal to the surface, whereas the (111) axes of the crystallites are randomly oriented. No amorphisation or tilt of this fibre texture was observed with increasing pulse bias. The homogeneity over 4" is better than 2%. The resistivity of the layers is between 300 and 70 μΩcm, depending on the deposition conditions

Surface and Coatings Technology, 2000

Aluminium nitride (AlN) thin films were deposited under different nitrogen partial and total pres... more Aluminium nitride (AlN) thin films were deposited under different nitrogen partial and total pressures by means of reactive d.c. magnetron sputtering. The investigated films had polycrystalline structure, revealed by electron beam diffraction (EBD). The depth profiles of Al, N and C distributions were registered by a direct emission layer-by-layer analysis in a hollow cathode glow discharge. All data indicated that there are no peculiarities of the element depth profiles in our films. The X-ray photoelectron spectroscopy (XPS) spectrum was used to determine the composition of the films. The spectrum clearly showed peaks from Al, N, O and C atoms present in the films. The electrochemical behaviour of the films was investigated using a d.c. electrochemical test in a 3% NaCl solution. The AlN films grown at a higher nitrogen partial pressure performed with a better electrochemical behaviour. A strong IR absorption band was obtained around 670cm−1, which confirmed that the deposited films were AlN.

Plasma Sources Science and Technology

... This method combines the advantages of plasma treatments, like plasma nitriding [4] and ionim... more ... This method combines the advantages of plasma treatments, like plasma nitriding [4] and ionimplantation [5], in one method: the modification of complex ... Only the upper 50 mm were made of conducting titanium, the lower part consisted of insulating alumina to reduce the total ...

Surface and Coatings Technology, 2008

Physical vapour deposition with energetic ions is an established technology for creating function... more Physical vapour deposition with energetic ions is an established technology for creating functional surfaces where changing morphologies are observed with increasing energy deposition. In this presentation, magnetron sputtering (MS) is compared with ion beam sputtering (IBS) and vacuum arc deposition (VAD) for corrosion resistant Mg coatings. With increasing average energy flux along the three methods, a transition from a columnar growth regime towards a layer-by-layer growth at increased energies was observed, while a basal texture with the c-axis normal to the surface was found in all cases. However, the full width at half maximum (FWHM) of the corresponding Mg(002) rocking curves showed a pronounced minimum of 3° for IBS deposited films, apparently caused by the reflected high energy primary Ar + ions. For pure Mg films, no larger differences in the corrosion potential and the corrosion rates were measured.

Surface and Coatings Technology, 2008

Outstanding wear resistance of austenitic stainless steel after nitrogen insertion and formation ... more Outstanding wear resistance of austenitic stainless steel after nitrogen insertion and formation of expanded austenite in the temperature range below 420°C is a well established phenomena. However, detailed information on the wear mechanism for the modified surfaces is still missing. This paper presents the results of wear experiments performed in a dry oscillating geometry against a WC ball (diameter 3 mm, load 3 N), together with metallographic investigations of the resulting cross-sections, both with and without nitriding. Comparisons with calculated stress distributions indicate that those nitrided samples showing a specific wear reduction by a factor of about 100 were subjected to a combination of stress maxima within the surface layer and below the layer in the bulk material.

Martensitic stainless steel samples—1.4021 (X20Cr13), 1.4034 (X46Cr13), 1.4057 (X17CrNi16.2), 1.4... more Martensitic stainless steel samples—1.4021 (X20Cr13), 1.4034 (X46Cr13), 1.4057 (X17CrNi16.2), 1.4104 (X14CrMoS17) and 1.4542(X5CrNiCuNb17.4)—were implanted with nitrogen using plasma immersion ion implantation (PIII) at different temperatures between 320 and 380 °C and at different pulse voltages for up to 3 h. The formation of an expanded martensite layer was found after implantation for all samples with a surface martens hardness of

Applied Surface Science, 2014

ABSTRACT A novel steel 460Li–21Cr belonging to a new generation of superferritic grade steel has ... more ABSTRACT A novel steel 460Li–21Cr belonging to a new generation of superferritic grade steel has been implanted with nitrogen in a low power 13.56 MHz radio frequency plasma by the plasma immersion ion implantation (PIII) technique in order to study its physical and chemical properties under different experimental conditions. We observed improved hardness and wear behavior of 460Li–21Cr steel with a layer thickness between 1.5 and 4.0 μm after 60 min implantation in the temperature range from 350 to 550 °C. The modified surface layer containing nitrogen does not show CrN in X-ray diffraction (XRD). Compared to untreated substrates, the hardness can be increased by a factor of 4, depending on the experimental conditions, and the wear behavior was also improved by two orders of magnitude. The results are very similar to those for austenitic stainless steel with a similar pronounced increase in wear resistance and plateau-like nitrogen depth profiles.

Surface and Coatings Technology, 2008

We report on simultaneous (Al+ N) implantation of Al and N into layers of amorphous thermal silic... more We report on simultaneous (Al+ N) implantation of Al and N into layers of amorphous thermal silica (SiO2) in an attempt to bond Al with N and form the binary compound AlN. As an implantation technique, plasma ion immersion implantation (PIII) is used. The energy ...

Surface & Coatings Technology, 2005

In this work, nitrogen plasma immersion ion implantation (PIII) treatment of austenitic stainless... more In this work, nitrogen plasma immersion ion implantation (PIII) treatment of austenitic stainless steels 1.4301 and 1.4571 was performed to investigate the influence of the process conditions on the corrosion properties. Short treatment, high voltage and high temperature result in a decreased corrosion potential while no correlation to layer thickness, nitrogen concentration or lattice expansion was found. Except for the

Vacuum, 1998

AlN-films prepared by dc reactive magnetron sputtering. AlN in an Ar+N 2 gas mixture have been pr... more AlN-films prepared by dc reactive magnetron sputtering. AlN in an Ar+N 2 gas mixture have been prepared and their microstructure, hardness, refractive index and IR transmittance examined. At l = 640 nm the refractive index was 1.93 and k = 3×10 −3 ; high transmission occurred between [??] structure and oxygen on microhardness is discussed.

Surface and Coatings Technology, 2014

ABSTRACT The formation of expanded austenite after nitrogen insertion into austenitic stainless s... more ABSTRACT The formation of expanded austenite after nitrogen insertion into austenitic stainless steel, CoCr or Ni base alloys is still not completely understood. Ex situ X-ray diffraction (XRD) investigations, which can be very sophisticated nowadays, lack the exact time evolution while additional annealing processes may occur during cooling phases. Furthermore a time resolution of a few minutes is required, necessitating modern detectors. After mastering the challenge of building such equipment, in situ experiments can lead to a multitude of information which can be used to reassess current models. Here, a critical discussion about the topics where these in situ XRD investigations during low energy ion implantation (LEII) can help for further understanding and where they cannot help is presented. Especially, the following subjects are addressed: (i) influence of ion current density and grain orientation on diffusion and phase formation, (ii) decay of expanded austenite, (iii) correlation between lattice expansion and nitrogen content, and (iv) mechanical deformation of expanded austenite. While results on the first two points can be readily obtained, additional, external information on the nitrogen content and the orientation distribution function of grains is necessary for the latter two points, respectively.

Surface and Coatings Technology, 2012

Using a pulse low energy ion implantation with an electronic beam switch operating in the kHz reg... more Using a pulse low energy ion implantation with an electronic beam switch operating in the kHz regime, a more efficient nitriding process is possible than with either pulsed plasma immersion ion implantation (PIII) or continuous low energy ion implantation (LEII). Using such an experimental setup, it is shown that the pulse length modulation (PLM) itself produces a slight beneficial effect on the corrosion behaviour of austenitic stainless steel 316 L at 400°C. However, differences in the diffusion and phase formation exist. For 5% PLM, a lower nitrogen flux resulted in the formation of expanded austenite with a very low lattice expansion, while the highest PLM (40%) led to a reduced layer thickness caused by higher sputtering induced by the increased ion bombardment itself. Nitriding at 400°C increases the corrosion resistance of 316 L stainless steel for all PLM. The effect is more pronounced for 15 and 30% PLM

Surface and Coatings Technology, 2011

By inserting an auxiliary rf plasma source in an experimental setup for depositing TiO 2 thin fil... more By inserting an auxiliary rf plasma source in an experimental setup for depositing TiO 2 thin films with a cathodic vacuum arc and high voltage pulses, i.e. metal plasma immersion ion implantation & deposition (MePIIID), it is shown that this auxiliary plasma source can increase the growth rate at low gas flow ratios only but not increase the oxygen/titanium ratio. It can be surmised that the plasma source creates activated oxygen species which are otherwise supplied from collisions of the titanium plasma stream with the background gas at higher pressures.

Surface and Coatings Technology, 2011

Using a pulse low energy ion implantation with an electronic beam switch operating in the kHz reg... more Using a pulse low energy ion implantation with an electronic beam switch operating in the kHz regime, a more efficient nitriding process is possible than with either pulsed plasma immersion ion implantation (PIII) or continuous low energy ion implantation (LEII). Besides the pulsed mode, a fast and precise external heating system for controlling the substrate temperature is necessary. Using such

Surface and Coatings Technology, 2011

Vegard's law provides a rule of thumb for equilibrium stress-free lattice constants in nitri... more Vegard's law provides a rule of thumb for equilibrium stress-free lattice constants in nitrided austenitic stainless steel and CoCr alloys. However, when taking the austenitic, metallic phase and stoichiometric FeN or CoN phases as endpoints, the resulting calculated expansions are too high compared with experiments. When extrapolating a linear equation taken from literature for very low nitrogen concentrations in steel,

Surface and Coatings Technology, 2004

Surface and Coatings Technology, 2014

ABSTRACT The formation of expanded austenite after nitrogen insertion into austenitic stainless s... more ABSTRACT The formation of expanded austenite after nitrogen insertion into austenitic stainless steel, CoCr or Ni base alloys is characterised by an unusually high nitrogen content in solid solution representing a diffusion layer. However, the process is still not completely understood. Using in situ X-ray diffraction (XRD) experiments and additional data from SEM, the phase formation and diffusion after low energy nitrogen ion implantation into commercial Ni80Cr20 (Nichrome) are investigated in the temperature range from 350 to 500 °C. A compound layer consisting of a phase similar to fct Ni4N is formed on the surface, most likely with a composition of (Ni,Cr)4N, followed by a diffusion zone extending about 1 μm into the material. For increasing temperature, the total nitrogen uptake is decreasing. The time evolution shows that a saturation is reached earlier for higher temperatures whereas no saturation has been found for 375 °C and 90 min. A competition exists between nitrogen loss at the surface and nitrogen supply by the ion beam. This loss process is thermally activated and depends on the surface orientation. Additionally, at 500 °C some CrN precipitates are found.

2000 International Conference on Ion Implantation Technology Proceedings. Ion Implantation Technology - 2000 (Cat. No.00EX432), 2000

ABSTRACT In this report the formation of textured and dense TiN films on Si by MePIID at room tem... more ABSTRACT In this report the formation of textured and dense TiN films on Si by MePIID at room temperature is investigated. The high voltage pulses with duty cycles of 9% were varied between 0 and 10 kV. The growth rates of a few nanometers per second, depending on the arc current, were calculated using results from elastic recoil detection analysis (ERDA). Using resonant Rutherford backscattering spectroscopy (RRBS), contamination levels of less than 0.5% oxygen were determined. With X-ray diffraction (XRD) and pole figure measurements a highly oriented TiN phase was observed for all bias voltages. The (200) axis is normal to the surface, whereas the (111) axes of the crystallites are randomly oriented. No amorphisation or tilt of this fibre texture was observed with increasing pulse bias. The homogeneity over 4" is better than 2%. The resistivity of the layers is between 300 and 70 μΩcm, depending on the deposition conditions

Surface and Coatings Technology, 2000

Aluminium nitride (AlN) thin films were deposited under different nitrogen partial and total pres... more Aluminium nitride (AlN) thin films were deposited under different nitrogen partial and total pressures by means of reactive d.c. magnetron sputtering. The investigated films had polycrystalline structure, revealed by electron beam diffraction (EBD). The depth profiles of Al, N and C distributions were registered by a direct emission layer-by-layer analysis in a hollow cathode glow discharge. All data indicated that there are no peculiarities of the element depth profiles in our films. The X-ray photoelectron spectroscopy (XPS) spectrum was used to determine the composition of the films. The spectrum clearly showed peaks from Al, N, O and C atoms present in the films. The electrochemical behaviour of the films was investigated using a d.c. electrochemical test in a 3% NaCl solution. The AlN films grown at a higher nitrogen partial pressure performed with a better electrochemical behaviour. A strong IR absorption band was obtained around 670cm−1, which confirmed that the deposited films were AlN.

Plasma Sources Science and Technology

... This method combines the advantages of plasma treatments, like plasma nitriding [4] and ionim... more ... This method combines the advantages of plasma treatments, like plasma nitriding [4] and ionimplantation [5], in one method: the modification of complex ... Only the upper 50 mm were made of conducting titanium, the lower part consisted of insulating alumina to reduce the total ...

Surface and Coatings Technology, 2008

Physical vapour deposition with energetic ions is an established technology for creating function... more Physical vapour deposition with energetic ions is an established technology for creating functional surfaces where changing morphologies are observed with increasing energy deposition. In this presentation, magnetron sputtering (MS) is compared with ion beam sputtering (IBS) and vacuum arc deposition (VAD) for corrosion resistant Mg coatings. With increasing average energy flux along the three methods, a transition from a columnar growth regime towards a layer-by-layer growth at increased energies was observed, while a basal texture with the c-axis normal to the surface was found in all cases. However, the full width at half maximum (FWHM) of the corresponding Mg(002) rocking curves showed a pronounced minimum of 3° for IBS deposited films, apparently caused by the reflected high energy primary Ar + ions. For pure Mg films, no larger differences in the corrosion potential and the corrosion rates were measured.

Surface and Coatings Technology, 2008

Outstanding wear resistance of austenitic stainless steel after nitrogen insertion and formation ... more Outstanding wear resistance of austenitic stainless steel after nitrogen insertion and formation of expanded austenite in the temperature range below 420°C is a well established phenomena. However, detailed information on the wear mechanism for the modified surfaces is still missing. This paper presents the results of wear experiments performed in a dry oscillating geometry against a WC ball (diameter 3 mm, load 3 N), together with metallographic investigations of the resulting cross-sections, both with and without nitriding. Comparisons with calculated stress distributions indicate that those nitrided samples showing a specific wear reduction by a factor of about 100 were subjected to a combination of stress maxima within the surface layer and below the layer in the bulk material.

Martensitic stainless steel samples—1.4021 (X20Cr13), 1.4034 (X46Cr13), 1.4057 (X17CrNi16.2), 1.4... more Martensitic stainless steel samples—1.4021 (X20Cr13), 1.4034 (X46Cr13), 1.4057 (X17CrNi16.2), 1.4104 (X14CrMoS17) and 1.4542(X5CrNiCuNb17.4)—were implanted with nitrogen using plasma immersion ion implantation (PIII) at different temperatures between 320 and 380 °C and at different pulse voltages for up to 3 h. The formation of an expanded martensite layer was found after implantation for all samples with a surface martens hardness of

Applied Surface Science, 2014

ABSTRACT A novel steel 460Li–21Cr belonging to a new generation of superferritic grade steel has ... more ABSTRACT A novel steel 460Li–21Cr belonging to a new generation of superferritic grade steel has been implanted with nitrogen in a low power 13.56 MHz radio frequency plasma by the plasma immersion ion implantation (PIII) technique in order to study its physical and chemical properties under different experimental conditions. We observed improved hardness and wear behavior of 460Li–21Cr steel with a layer thickness between 1.5 and 4.0 μm after 60 min implantation in the temperature range from 350 to 550 °C. The modified surface layer containing nitrogen does not show CrN in X-ray diffraction (XRD). Compared to untreated substrates, the hardness can be increased by a factor of 4, depending on the experimental conditions, and the wear behavior was also improved by two orders of magnitude. The results are very similar to those for austenitic stainless steel with a similar pronounced increase in wear resistance and plateau-like nitrogen depth profiles.

Surface and Coatings Technology, 2008

We report on simultaneous (Al+ N) implantation of Al and N into layers of amorphous thermal silic... more We report on simultaneous (Al+ N) implantation of Al and N into layers of amorphous thermal silica (SiO2) in an attempt to bond Al with N and form the binary compound AlN. As an implantation technique, plasma ion immersion implantation (PIII) is used. The energy ...

Surface & Coatings Technology, 2005

In this work, nitrogen plasma immersion ion implantation (PIII) treatment of austenitic stainless... more In this work, nitrogen plasma immersion ion implantation (PIII) treatment of austenitic stainless steels 1.4301 and 1.4571 was performed to investigate the influence of the process conditions on the corrosion properties. Short treatment, high voltage and high temperature result in a decreased corrosion potential while no correlation to layer thickness, nitrogen concentration or lattice expansion was found. Except for the

Vacuum, 1998

AlN-films prepared by dc reactive magnetron sputtering. AlN in an Ar+N 2 gas mixture have been pr... more AlN-films prepared by dc reactive magnetron sputtering. AlN in an Ar+N 2 gas mixture have been prepared and their microstructure, hardness, refractive index and IR transmittance examined. At l = 640 nm the refractive index was 1.93 and k = 3×10 −3 ; high transmission occurred between [??] structure and oxygen on microhardness is discussed.

Surface and Coatings Technology, 2014

ABSTRACT The formation of expanded austenite after nitrogen insertion into austenitic stainless s... more ABSTRACT The formation of expanded austenite after nitrogen insertion into austenitic stainless steel, CoCr or Ni base alloys is still not completely understood. Ex situ X-ray diffraction (XRD) investigations, which can be very sophisticated nowadays, lack the exact time evolution while additional annealing processes may occur during cooling phases. Furthermore a time resolution of a few minutes is required, necessitating modern detectors. After mastering the challenge of building such equipment, in situ experiments can lead to a multitude of information which can be used to reassess current models. Here, a critical discussion about the topics where these in situ XRD investigations during low energy ion implantation (LEII) can help for further understanding and where they cannot help is presented. Especially, the following subjects are addressed: (i) influence of ion current density and grain orientation on diffusion and phase formation, (ii) decay of expanded austenite, (iii) correlation between lattice expansion and nitrogen content, and (iv) mechanical deformation of expanded austenite. While results on the first two points can be readily obtained, additional, external information on the nitrogen content and the orientation distribution function of grains is necessary for the latter two points, respectively.

Surface and Coatings Technology, 2012

Using a pulse low energy ion implantation with an electronic beam switch operating in the kHz reg... more Using a pulse low energy ion implantation with an electronic beam switch operating in the kHz regime, a more efficient nitriding process is possible than with either pulsed plasma immersion ion implantation (PIII) or continuous low energy ion implantation (LEII). Using such an experimental setup, it is shown that the pulse length modulation (PLM) itself produces a slight beneficial effect on the corrosion behaviour of austenitic stainless steel 316 L at 400°C. However, differences in the diffusion and phase formation exist. For 5% PLM, a lower nitrogen flux resulted in the formation of expanded austenite with a very low lattice expansion, while the highest PLM (40%) led to a reduced layer thickness caused by higher sputtering induced by the increased ion bombardment itself. Nitriding at 400°C increases the corrosion resistance of 316 L stainless steel for all PLM. The effect is more pronounced for 15 and 30% PLM

Surface and Coatings Technology, 2011

By inserting an auxiliary rf plasma source in an experimental setup for depositing TiO 2 thin fil... more By inserting an auxiliary rf plasma source in an experimental setup for depositing TiO 2 thin films with a cathodic vacuum arc and high voltage pulses, i.e. metal plasma immersion ion implantation & deposition (MePIIID), it is shown that this auxiliary plasma source can increase the growth rate at low gas flow ratios only but not increase the oxygen/titanium ratio. It can be surmised that the plasma source creates activated oxygen species which are otherwise supplied from collisions of the titanium plasma stream with the background gas at higher pressures.

Surface and Coatings Technology, 2011

Using a pulse low energy ion implantation with an electronic beam switch operating in the kHz reg... more Using a pulse low energy ion implantation with an electronic beam switch operating in the kHz regime, a more efficient nitriding process is possible than with either pulsed plasma immersion ion implantation (PIII) or continuous low energy ion implantation (LEII). Besides the pulsed mode, a fast and precise external heating system for controlling the substrate temperature is necessary. Using such

Surface and Coatings Technology, 2011

Vegard's law provides a rule of thumb for equilibrium stress-free lattice constants in nitri... more Vegard's law provides a rule of thumb for equilibrium stress-free lattice constants in nitrided austenitic stainless steel and CoCr alloys. However, when taking the austenitic, metallic phase and stoichiometric FeN or CoN phases as endpoints, the resulting calculated expansions are too high compared with experiments. When extrapolating a linear equation taken from literature for very low nitrogen concentrations in steel,

Surface and Coatings Technology, 2004