Serbian society for microscopy Academy of medical sciences SMS LABORATORY

							Serbian society for microscopy                     Academy of medical sciences, SMS


 LABORATORY FOR HEAT TREATMENT AND SURFACE
                      ENGINEERING
    Faculty of Technical Sciences, University of Novi Sad
                       Damir Kakaš, Branko Škorić,
             Tamara Novakov, Lazar Kovačević, Aleksandar Miletić

1. HISTORY

     Laboratory for heat treatment and surface engineering was founded in 1971, first
as the Laboratory for heat treatment and in 1991 surface engineering was added to the
former name as one of the completely new areas and one of the most important courses
of science development in the world. The intensive use of electron microscopy started
in 1978, when the first electron microscope was acquired at the University. Today, the
University possesses high quality equipment which we extensively use for scientific
research as well as for problems solving in matters related to the cooperation with other
companies.
     The staff of the laboratory for heat treatment is: Professor Dr. Damir Kakas (chief
of laboratory), associated professor Branko Skoric, teaching assistant Tamara
Novakov, assistant researchers Lazar Kovacevic, Aleksandar Miletic and Marko
Vilotic. Dragisa Lupuljev, MSc, Rakita Milan MSc and Ljiljana Mazibrada who have
taken up other, more up-and-coming jobs, should be mentioned as well since they have
done a lot of work on the microscope and have published many papers related to those
investigations.
     The laboratory for heat treatment has had a fruitful cooperation with the Institute
of Slovenian Bloomeries from Ljubljana (from 1980-1990), especially regarding the
use of the electronic micro analyser JEOL - with Professor Lado Kosec. We have also
had a long cooperation with our colleague Dr. Natasa Bibic, from the Vinca Institute.
Since 1997, our work has been done in cooperation with the Nikola Tesla Centre from
the Vinca Institute, therefore most of our work is conducted in Belgrade, however,
some of the specific problems have been solved in cooperation with Dr. Wolfgang
Bohne from the Haihn-Meitner Institute in Berlin, Dr. Gregor M from the BIONT, a.s.,
Department of Nanotechnologies in Bratislava, Dr.G. Favaro CSM Instruments SA
Peseux from Switzerland and others.

2. RESEARCH

Investigation the process of aluminium coating

     During the period of 1980-1981 very detailed research has been conducted
regarding the influence of parameters of the aluminium coating process on the effects
of diffusion processes and structural changes within the diffusion layer. The key
research involved the use of the electron micro analyser where results of linear analysis
of the change in Fe, Al and Si composition, within the diffusion layer, and the results

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of the dot analysis of some elements, at the cross section, were obtained (Fig 1). The
analyzed area was 100x100µm and the obtained results were of the vital importance for
optimisation of the aluminium coating process as well as for explaining the behaviour
of obtained coatings after the effect of high temperature corrosion [1], [2].




          Fig. 1. Aluminium coated sample in Al-Si alloy – T=780ºC, t=10min, S=0,4 [2]

     Plasma nitriding

      Plasma nitriding is a method for surface improvement of steel which was at the
peak of development around the globe during the 1980's while we had started to do
research in this area in 1979. Around 20 papers have been published in internationally,
and two papers, [3], [4] stand out. They have been the result of systematic research of
the influence of surface modifications on tool life increase as the function of tool
design parameters, plasma nitriding parameters and the influence of some exploatation
conditions. On of the key problems were investigations of the change in tool geometry
in the areas of maximum pressures and flow processes of raw material over the tool
edges. These phenomena were investigated by measuring of replicas obtained after a
tool had been working for a particular time and by SEM analysis after the use of the
tool. The SEM analysis made it possible for us to clearly comprehend the changes in
tool geometry and quality of the processed samples during the exploitation of the tool,
which had enabled us to optimise the process of tool design and process of plasma
nitriding as well as to solve particular problems of the modern industry.




       Fig. 2. Surface of stamp for backward extrusion [4]: a) macro view of stamp head, b)
        wear traces at upper side of the head, b) wear traces on the side of the head

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Serbian society for microscopy                      Academy of medical sciences, SMS
     Development of heat treatment of the ADI

      Austempered ductile iron is the material which has been extensively investigated
during the 1980 and 1990's. We have done systematic, broad research of correlation of
temperature and duration of heating, temperature and duration of austempering on the
quality of ADI materials, mainly, hardness, structure and toughness. Figures show the
fracture surface of ADI material for three different kinds of heat treatment, as an
illustration of how the quality can be modified only by changing the above mentioned
parameters [5].




          Fig. 3. Surface of fractured ADI samples [5]: a) austempered at 400ºC for 1h,
                b) austempered at 300ºC for 1h, c) austempered at 300ºC for 2,2h

     Development of duplex coatings

      Duplex coatings have been investigated in our laboratory since 1990, where we
were one of the first people to start research in this field. First papers date back to
1989, and in this paper we will cite two papers which have been published in leading
international journals in the mid 1990's [6], [7]. The point of duplex coatings is the
combination of the method for increasing load bearing capacity of the surface layer,
but also, obtaining first-class wear resistance of the surface. For example, we have
conducted plasma nitriding of the surface of construction steels where we have raised
the hardness value from 250HV (in austempered condition) to 1100HV (plasma
nitrided). After additional deposition of TiN or TiAlN we got surface hardness in the
range of 2000-3900 HV, depending on the deposition process parameters. These results
enable the use of constructive steels for new generation transmissions.

     Development of IBAD (Ion Beam Assisted Deposition)

     Today, researchers from the laboratory are investigating the development of
IBAD and obtaining of first-class coatings of the highest quality which was not
possible to do until now. In order to get the highest adhesion and resistance to impact
load, we, today, make coatings with nano interfaces and interlayers obtained by the
process of Ion Beam Mixing. As the result of IBAD technology, the surface layer has a
mono orientation regulated by additional bombardment by Ar ions, we obtained a
material which has a hard core (alloyed carburising steel), we managed to get high load
bearing capacity of the surface thanks to the 01-05 mm thick carburized layer while we
have deposited an IBAD coating with the highest adhesion and a remarkably low

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Serbian society for microscopy                           Academy of medical sciences, SMS
friction coefficient [8]. The evidence of the good adhesion are the figures obtained by
SEM which show no delamination at the edges of the scratch test track. Only at the end
of the track, where the load is close to 100N, minimal tracks of coating failure can be
seen. It is important to note that with traditional deposition techniques, coatings with
first signs of spallation between 25 and 40N can be obtained, when deposited on the
same steel.




      Fig. 4. a) the middle of the scratch test, b) the end of the scratch test, c) EDS analysis of
  another sample with significant spallation in order to identify the material at the middle of
                                       the track [in press]

3. REFERENCES:

[1] Kakaš D., Some improvement in aluminium coating, XXIV Seminar of IPM,
    Warsaw, (1984) (invited paper), Proc. - p.87-97
[2] Kakaš D.,Vidojevic N., Novovic-Simovic N., Influence of dimension and
    composition of Ai-Si coating layer on high temperature corrosion resistance of
    steel, 2nd International Congress on Heat Treatment of Metals, Florence, (1982),
    Proceedings p. 391-401.
[3] Kakaš D.,Lupuljev D., Veselinovic C., Zlatanovic M., Influence of ion nitriding
    parameters on cold forming tools quality, 5th Inter.Congress on Heat Treatment of
    Materials, Budapest, (1986) Proceedings .Vol. II - p.998-1005.
[4] Kakaš D., Lupuljev D., Zlatanovic M., Contribution to investigation of plasma
    nitriding on tools for cold working., 1st International Seminar on Plasma Heat
    Treatment, Senlis near Paris, (1987), Proc. - p.353-364
[5] Kakaš D., Bajic V., Šidjanin L., Influence of the heat treatment of ADI on
    structure changes and wear resistance 5. Jugoslovenski Simp. o Term. Obradi, V.
    Banja, (1989). Zbornik str. 190-195.
[6] Zlatanović M., Kakaš D., Mažibrada Lj., Kunosić A., Munz W.D., - Surface and
    Coating Technology, 64 (1994) p.173 – 181.
[7] Škorić B., Kakaš D., Tribologycal behaviour of TiN and TiAlN deposited layers
    on substrates plasma nitrided at low pressure, Materials and Manufacturing
    Processes, Vol 10, 1 ,(1995), 133-138
[8] Kakaš D., Škorić B., Rakita M., Tribological behavior of duplex coating improved
    by ion implantation, Thin Solid Films, Volume 459, Issues 1-2, (2004), 152-155.
[9] D. Kakaš, B. Škorić, T. Novakov, M. Rakita, W. Bohne, M. Gregor, N. Nešković,
    A. Dobrosavljević, Nanomodification of steel surface by krypton, Proceedings of
    1st International Workshop on Nanoscience & nanotechnology, Belgrade, Serbia
    and Montenegro, (2005), p. 186-190

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