# Knowledge base: Warsaw University of Technology

Back

## Synteza warstw azotkowych w zmodyfikowanych warunkach generacji plazmy impulsowej metodą IPD

### Rafał Chodun

#### Abstract

This doctoral thesis concerns the characterization of the effects of the application of impulse gas concentration variation, carried out by gas injection by impulse valve system, providing gas in individual doses, to the discharge region of impulse plasma coaxial accelerator in the IPD method (Impulse Plasma Deposition) of coatings synthesis. Subject of thesis, which is an element of a broader research topic being developed in a research team led by prof. Krzysztof Zdunek, associated with the concept of impulse gas concentration variation and its actual role in the field of plasma synthesis of coatings by surface engineering methods, focuses on physical - chemical state of the coating/substrate interface forming in the deposition process of “valve” modified IPD method (in previous standard of IPD method, working gas is distributed continuously and dynamic value of the working pressure in the deposition chamber does not vary). The starting point for the formulation of research hypothesis were extremely good results of the durability tests of cutting tools coated with titanium nitride, deposited during the modified IPD process - proved in the test, that the durability of the edges has increased even sixteen-fold compared to the life time of uncoated ones. On this basis, the following research hypothesis was formulated: "The application of the gas injecting in the process of the impulse plasma generation in IPD method leads to an increase of the efficiency of this method for the synthesis of nitrides coatings, concerning for example, the anti-wear properties of these coatings". In scope of the objectives for further researches, were: - the characterization of manifestation of "efficiency" of modified IPD method, which discerned within the parameters of plasma state generated and expanded in the changed conditions of working gas; - effectiveness in terms of formation of the state of deposit and substrate, with a particular focusing on phase boundary region. The plasma dynamics simulation studies showed an increase in the kinetics of spreading the plasmoid under dynamically reducing pressure conditions, what is more, in these conditions, the plasma species acquired higher energies, what also has been confirmed experimentally by the Langmuir probe diagnostics. Based on the diagnostics of electric circuit of modified plasma source the well – optimized operation of erosive regime was observed, which turned out to be a consequence of the applied modification. The advanced spectroscopic studies of impulse plasma showed two - zone structure of spreading plasmoids, which front side was composed mainly from the products of erosion and subsequent excitation of accelerator electrode material, and the back side was composed from product of working gas excitation. As part of these studies, a very energetic plasma emission spectrum has been measured some of the plasma components reached the fourth degree of ionization. In conclusion, the impulse plasma pulse generated and spread in the dynamic conditions of the gas dosing is more energetic in both meanings of energy, kinetic and potential, comparing to the impulse plasma generated under the "standard" conditions. The use of gas injections was also reflected in the process of phase nucleation and the model of coatings growth. Decreasing the pressure during the process of deposition makes the phase to nucleate on the substrate by heterogeneous mechanism, not on the plasma ions as during standard IPD method; while the coating growth mechanism is no longer “cluster mechanism” - as studies have shown, the deposited coatings have a nanocrystalline, amorphous phase devoid structure, dense and compacted, and do not have typical columnar structure. The studies of phase boundary region characterization showed, that the interface has a complex chemical structure. Straight under the nitride coating, the presence of a thin zone of the substrate material, highly enriched by products of erosion of accelerator electrodes was found. In the emission spectra, measured on the substrate surface, exposed to the energetic impact of the plasma pack, the presence of sputtered and excited species were found. On this basis, it has been hypothesized for shallow implantation (subplantation) of plasma ions in the substrate with the presence of the competing phenomena of partial sputtering and subsequent re-condensation. Microhardness tests showed an increase of the mechanical properties at the interface zone. Studies showed that the efficiency of the nitrides coatings synthesis under the modified conditions of the plasma process is the origin in the energy of plasma components increase, which has a significant impact on the properties of the product of synthesis, both in terms of its structure morphology and its high adhesion to the substrate
Record ID
Diploma type
Doctor of Philosophy
Author
Title in Polish
Synteza warstw azotkowych w zmodyfikowanych warunkach generacji plazmy impulsowej metodą IPD
Language
(pl) Polish
Certifying Unit
Faculty of Materials Science and Engineering (FMSE)
Discipline
material sciences and engineering / (technology domain) / (technological sciences)
Status
Finished
Start date
18-06-2010
Defense Date
15-04-2014
Title date
15-04-2014
Supervisor
Internal reviewers
External reviewers
Jan Walkowicz Jan Walkowicz,, External affiliation of publication: Politechnika Koszalińska
Pages
207
Keywords in English
metoda IPD, plazma impulsowe, Warstwy przeciwzużyciowe, warstwy nanokrystaliczne
Abstract in English
This doctoral thesis concerns the characterization of the effects of the application of impulse gas concentration variation, carried out by gas injection by impulse valve system, providing gas in individual doses, to the discharge region of impulse plasma coaxial accelerator in the IPD method (Impulse Plasma Deposition) of coatings synthesis. Subject of thesis, which is an element of a broader research topic being developed in a research team led by prof. Krzysztof Zdunek, associated with the concept of impulse gas concentration variation and its actual role in the field of plasma synthesis of coatings by surface engineering methods, focuses on physical - chemical state of the coating/substrate interface forming in the deposition process of “valve” modified IPD method (in previous standard of IPD method, working gas is distributed continuously and dynamic value of the working pressure in the deposition chamber does not vary). The starting point for the formulation of research hypothesis were extremely good results of the durability tests of cutting tools coated with titanium nitride, deposited during the modified IPD process - proved in the test, that the durability of the edges has increased even sixteen-fold compared to the life time of uncoated ones. On this basis, the following research hypothesis was formulated: "The application of the gas injecting in the process of the impulse plasma generation in IPD method leads to an increase of the efficiency of this method for the synthesis of nitrides coatings, concerning for example, the anti-wear properties of these coatings". In scope of the objectives for further researches, were: - the characterization of manifestation of "efficiency" of modified IPD method, which discerned within the parameters of plasma state generated and expanded in the changed conditions of working gas; - effectiveness in terms of formation of the state of deposit and substrate, with a particular focusing on phase boundary region. The plasma dynamics simulation studies showed an increase in the kinetics of spreading the plasmoid under dynamically reducing pressure conditions, what is more, in these conditions, the plasma species acquired higher energies, what also has been confirmed experimentally by the Langmuir probe diagnostics. Based on the diagnostics of electric circuit of modified plasma source the well – optimized operation of erosive regime was observed, which turned out to be a consequence of the applied modification. The advanced spectroscopic studies of impulse plasma showed two - zone structure of spreading plasmoids, which front side was composed mainly from the products of erosion and subsequent excitation of accelerator electrode material, and the back side was composed from product of working gas excitation. As part of these studies, a very energetic plasma emission spectrum has been measured some of the plasma components reached the fourth degree of ionization. In conclusion, the impulse plasma pulse generated and spread in the dynamic conditions of the gas dosing is more energetic in both meanings of energy, kinetic and potential, comparing to the impulse plasma generated under the "standard" conditions. The use of gas injections was also reflected in the process of phase nucleation and the model of coatings growth. Decreasing the pressure during the process of deposition makes the phase to nucleate on the substrate by heterogeneous mechanism, not on the plasma ions as during standard IPD method; while the coating growth mechanism is no longer “cluster mechanism” - as studies have shown, the deposited coatings have a nanocrystalline, amorphous phase devoid structure, dense and compacted, and do not have typical columnar structure. The studies of phase boundary region characterization showed, that the interface has a complex chemical structure. Straight under the nitride coating, the presence of a thin zone of the substrate material, highly enriched by products of erosion of accelerator electrodes was found. In the emission spectra, measured on the substrate surface, exposed to the energetic impact of the plasma pack, the presence of sputtered and excited species were found. On this basis, it has been hypothesized for shallow implantation (subplantation) of plasma ions in the substrate with the presence of the competing phenomena of partial sputtering and subsequent re-condensation. Microhardness tests showed an increase of the mechanical properties at the interface zone. Studies showed that the efficiency of the nitrides coatings synthesis under the modified conditions of the plasma process is the origin in the energy of plasma components increase, which has a significant impact on the properties of the product of synthesis, both in terms of its structure morphology and its high adhesion to the substrate
Thesis file
• File: 1
Chodun.pdf
Request a WCAG compliant version
Citation count
2

Uniform Resource Identifier
urn:pw-repo:WUT1bad8803815f4a07adb7dcc8081430d0