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Wyszukujesz frazę "Gospodinov, D. D." wg kryterium: Autor


Wyświetlanie 1-3 z 3
Tytuł:
Hardfacing of metal-cutting tools by arc welding in vacuum
Autorzy:
Ferdinandov, N. V.
Gospodinov, D. D.
Powiązania:
https://bibliotekanauki.pl/articles/368817.pdf
Data publikacji:
2020
Wydawca:
Stowarzyszenie Komputerowej Nauki o Materiałach i Inżynierii Powierzchni w Gliwicach
Tematy:
tool materials
wear resistance
hardfacing
heat treatment
hollow cathode arc
materiały narzędziowe
odporność na zużycie
napawanie
obróbka cieplna
katoda wnękowa łukowa
Opis:
Purpose: To present a technology for hardfacing of metal-cutting tools by arc welding in vacuum. Design/methodology/approach: The experiments were carried out using an installation for arc welding in vacuum. Objects of research were metal cutting tools (lathe knives), made of high-speed steel HS6-5-2 on a base metal of structural steel C45. The structure, hardness and wear resistance after hardfacing and after a triple tempering at 560°C have been determined. The heat resistance of the obtained instruments has been examined. Findings: The microstructural analysis showed that the structure of the built-up layer consisted of martensite, retained austenite and carbides. This was confirmed by the values of measured hardness after welding which were about 63-64 HRC. The triple tempering led to an increase in hardness by 3-4 HRC. It was found that the built-up layers (cutting edges of tools) retain their hardness (HRC=63-65) up to a temperature of 615-620°C, which shows that the heat resistance of the build-up layers was similar to that of the hardened and tempered tools of the same steel. The built-up work-pieces (excluding heat treated) and the reference knife showed the same cutting qualities at cutting speeds in the range of 55 to 120 m/min. It has been found that triple tempering after hardfacing led to increased wear resistance and consequently the durability of the tool also increased due to the higher hardness. Practical implications: The practical application is related to the production of metalcutting tools. Originality/value: The proposed technological method allows to produce defects free built-up layers. The cutting properties of the built-up in vacuum layers are comparable to or better than those of new tools made of steel HS 6-5-2.
Źródło:
Journal of Achievements in Materials and Manufacturing Engineering; 2020, 99, 2; 49-56
1734-8412
Pojawia się w:
Journal of Achievements in Materials and Manufacturing Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Structure and electrochemical behaviour of weldments of titanium Grade 1 in a bromine-containing solution
Autorzy:
Ilieva, M.D.
Ferdinandov, N.V.
Gospodinov, D.D.
Radev, R.H.
Powiązania:
https://bibliotekanauki.pl/articles/2175743.pdf
Data publikacji:
2021
Wydawca:
Stowarzyszenie Komputerowej Nauki o Materiałach i Inżynierii Powierzchni w Gliwicach
Tematy:
titanium Grade 1
hollow cathode arc discharge welding
electrochemical corrosion
cathodic loop
tytan Grade 1
spawanie łukowe z pustą katodą
korozja elektrochemiczna
pętla katodowa
Opis:
Purpose: The presented research aims to determine the microstructural changes in weldments of commercially pure titanium Grade 1 after welding by hollow cathode arc discharge in vacuum and related changes in the corrosion behaviour of the weldments. Design/methodology/approach: Macro and microstructure of weldments were studied using optical microscopy. Corrosion behaviour of untreated Grade 1 and heat-affected zone of weldments of Grade 1 was investigated using electrochemical testing, including open circuit potential measurements and potentiodynamic polarisation. As an aggressive environment, 1 M KBr water solution was used. Findings: Welding by hollow cathode arc discharge in vacuum leads to the formation of a coarse Widmanstätten structure in the heat-affected zone. This imperfect structure results in a passive layer with worsened protective properties, thus increasing the corrosion rate of weldments by up to two orders of magnitude compared to Grade 1 in as-received condition. The passive layer on the welded surfaces did not allow Grade 1 to acquire a stable corrosion potential during potenitodynamic polarization. Research limitations/implications: Titanium and its alloys are passivating metallic materials, and their corrosion resistance depends on the properties of a thin protective surface layer. Changes in the underlying metal microstructure can affect the passivation behaviour of titanium and the properties of this layer. Welding by hollow cathode arc discharge in vacuum alters the microstructure of heat-affected zone, thereby causing Widmanstätten microstructure to form. As the passive layer over that microstructure has worsened protective properties, we suggest additional heat treatment after welding to be applied. Future experimental research on this topic is needed. Originality/value: Welding by hollow cathode arc discharge in vacuum is a welding method allowing weldments to be done in a clean environment and even in space. In the specialised literature, information on the structure and corrosion resistance of weldments of commercially pure titanium Grade 1 welded by hollow cathode arc discharge in vacuum is missing. The present research fills in a tiny part of this gap in our knowledge.
Źródło:
Archives of Materials Science and Engineering; 2021, 112, 1; 5--12
1897-2764
Pojawia się w:
Archives of Materials Science and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Geodynamics of the South Balkans - seismotectonic model, fractality and nonlinear properties
Autorzy:
Ranguelov, B.
Dimitrova, S.
Gospodinov, D.
Lamykina, G.
Powiązania:
https://bibliotekanauki.pl/articles/224624.pdf
Data publikacji:
2006
Wydawca:
Politechnika Warszawska. Wydział Geodezji i Kartografii
Tematy:
geodynamika
sejsmika
Półwysep Bałkański
geodynamics
seismic
Balkan Peninsula
Źródło:
Reports on Geodesy; 2006, z. 5/80; 609-625
0867-3179
Pojawia się w:
Reports on Geodesy
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-3 z 3

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