Velko Rupetsov

Prof. Velko Rupetsov

Plovdiv University, Faculty of Phisics and Technology
orcid

Research Focus & Metrics

Academic Career Length

10Years (2017-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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11 November 2024 in Coatings
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Journal Article
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SRStanislava Rabadzhiyska
Stanislava Rabadzhiyska
DDDimitar Dechev
Dimitar Dechev
NINikolay Ivanov
Nikolay Ivanov
TIT. Ivanova
T. Ivanova
VSVelichka Strijkova
Velichka Strijkova
S. ValkovS. Valkov
S. Valkov
Zirconium nitrides films were synthesized on Ti6Al4V substrates at a bias voltage of −50 V, −80 V, −110 V and −150 V by the direct current (DC) reactive magnetron sputtering technique. The as-deposited coatings were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The wear and corrosion resistance of the obtained ZrN coatings were evaluated to determine the possibility for their implementation in modern biomedical applications. It was found that the intensity of the diffraction peak of the Zr-N phase corresponding to the (1 1 1) crystallographic plane rose as the bias voltage increased, while the ZrN coatings’ thickness reduced from 1.21 µm to 250 nm. The ZrN films’ surface roughness rose up to 75 nm at −150 V. Wear tests showed an increase in the wear rate and wear intensity as the bias voltage increased. Corrosion studies of the ZrN coatings were carried out by three electrochemical methods: open circuit potential (OCP), cyclic voltammetry (polarization measurements) and electrochemical impedance spectroscopy (EIS). All electrochemical measurements confirmed that the highest protection to corrosion is the ZrN coating, which was deposited on the Ti6Al4V substrate at a bias voltage of −150 V.

28 February 2017 in IOP Conference Series: Materials Science and Engineering
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VRVelko Rupetsov
Velko Rupetsov
GMGeorgi Mishev
Georgi Mishev
SDStefan Dishliev
Stefan Dishliev
VKViktor Kopanov
Viktor Kopanov
VCVassiliy Chitanov
Vassiliy Chitanov
CPChavdar Ognyanov Pashinski
Chavdar Ognyanov Pashinski
Injection molds used in production of plastic components are subject of heavy abrasion wear. The increase of their wear resistance significantly reduces the production cost. In the current work are presented research results of the wear resistance of injection molds made of steel 1.2343, coated with Ti/TiN/TiCN/nc-TiCN: a-C/nc-TiC:a -C/a-C. The study of the wear rate was done using the volumetric method and the influence of the trace length was investigated. The coating thickness, nanohardness, elastic modulus and adhesion were also tested. The coating was applied on unhardened ground specimens, hardened ground specimens and hardened polished specimens.

1 May 2019 in IOP Conference Series: Materials Science and Engineering
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Conference Paper
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IRI Radulescu
I Radulescu
ARA V Radulescu
A V Radulescu
SRS Ramalchanov
S Ramalchanov
SYS Yankov
S Yankov
VRVelko Rupetsov
Velko Rupetsov
Cutting fluids are used to reduce the negative effects of the heat and friction on both tool and work piece. The cutting fluids produce three positive effects in the process: heat removal elimination, lubrication on the chip–tool interface and chip removal. This paper proposes to study the rheological properties of four different type of cutting fluids, as function of their chemical and physical characteristics. The tests were performed using a cone and plate Brookfield viscometer, by determining the rheological parameters and the variation of the apparent viscosity with the temperature. This approach has been used to quantify the performance of the tested products and to compare products in the marketplace.

1 October 2019 in IOP Conference Series: Materials Science and Engineering
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VRVelko Rupetsov
Velko Rupetsov
LKLilyana Kolaklieva
Lilyana Kolaklieva
VCVassiliy Chitanov
Vassiliy Chitanov
MAMilko Angelov
Milko Angelov
Raycho Petrov RaychevRaycho Petrov Raychev
Raycho Petrov Raychev
CPChavdar Ognyanov Pashinski
Chavdar Ognyanov Pashinski
The application of Physical Vapor Deposition (PVD) hard coatings is one time-tested practice in the modern industry. Two of the main tendencies that promise a progress in this area are the combination of more chemical elements in one coating and the creation of nanolaminate structures. Since many combinations are possible in the design of the coatings, it could be expected they would have many different properties which are difficult to predict. In an attempt to work simultaneously in both of these directions, one nanolaminate Ti/TiN/AlTiSiN/(AlTiSiN/TiAlSiN)n/AlTiSiN coating was developed and its mechanical properties were tested. The results obtained give a reason to believe that it could be widely practically applied.

9 January 2018 in MATEC Web of Conferences
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Journal Article
Open access
TCTetiana Cholakova
Tetiana Cholakova
VCVasilliy Chitanov
Vasilliy Chitanov
LKLilyana Kolaklieva
Lilyana Kolaklieva
RKRoumen Kakanakov
Roumen Kakanakov
Konstantin BalashevKonstantin Balashev
Konstantin Balashev
GMGeorgi Mishev
Georgi Mishev
TiCrAlN and CrTiAlN multicomponent coatings have been developed using closed-field unbalanced magnetron sputtering technique (CFUBMS) in a gas mixture of Ar + N2. The nitrogen level was varied by using the feedback control of plasma optical emission monitor (OEM). An investigation into the effect of the CFUBMS process parameters on the properties of the coatings was undertaken. The main coatings parameters such as thickness, surface morphology, nanohardness, strength of adhesion and wear resistance were studied by means of ball-cratering method, atomic force microscopy, scanning electron microscopy, scratch tests and nanoindentation measurements. The study revealed strong dependency of the mechanical properties on the nitrogen flow rate. Analysis of the experimental results showed that Cr-based multicomponent coatings possess better mechanical properties than Ti-based coatings at a nitrogen flow rate of 21 sccm: higher value of hardness (≤ 31GPa) and higher scratch resistance (> 30 N).