The goal of this paper is to create metallic materials with superior functional performances. The layer obtained by electrode vibrator method must have a very good adherence on part surface and a high chemical and thermal compatibility with the substrate, as well as high ware and oxidation quality. So, in this paper Titan coating as interface and Wolfram as exterior layer were studied on ferito-perlitic cast-iron substrate. Pictures were taken with electronic scanning microscope

Anca-Elena LARGEANU

Carmen NEJNERU

Dan-Gelu GALUSCA

Manuela Cristina PERJU

Petrica VIZUREANU

The Annals of “Dunarea de Jos” University of Galati Fascicle IX Metallurgy and Materials Science

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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI. 
FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
N0. 1 – 2009, ISSN 1453 – 083X 
 
 
 
 
ANALYSIS OF TITANIUM INTERFACE AND TUNGSTEN  
EXTERIOR LAYER THICKNESS COATED BY VIBRATOR 
ELECTRODE METHOD  
 
Manuela Cristina PERJU, Dan-Gelu GALUSCA,  
Carmen NEJNERU, Petrica VIZUREANU, Anca-Elena LARGEANU 
Universitatea Tehnica “Gh.Asachi”, Iasi, Romania 
email: cryss_ela@yahoo.com 
 
ABSTRACT 
 
The goal of this paper is to create metallic materials with superior functional 
performances. The layer obtained by electrode vibrator method must have a very 
good adherence on part surface and a high chemical and thermal compatibility with 
the substrate, as well as high ware and oxidation quality. So, in this paper Titan 
coating as interface and Wolfram as exterior layer were studied on ferito-perlitic 
cast-iron substrate. Pictures were taken with electronic scanning microscope. 
 
KEYWORDS: electric spark alloying, layer thickness, metallic surface 
hardening, electronic scanning microscope 
 
1. Introduction 
 
Surface engineering does not refer to choosing 
and applying one of the many technologies available, 
for treating one part with a pre-established 
constructive shape, but in fact, surface engineering 
involves a new vision in fabricating and projecting 
activity.  
Through this concept mechanical parts are 
treated as composite systems, superficial layer – 
sublayer. Specific technologies are applied for 
proprieties modification for each element, to obtain in 
the end the wanted functional performances of the 
part. The life time of a machine, tool or installation is 
determined by the wear of the parts. Wear, fatigue and 
corrosion are the most aggressive factors that destroy 
a part.  
From all coating methods, metallic surfaces 
electro-spark alloying takes a good place because of 
the multitude of its advantages.  
The advantages are high adherence of these 
coatings with the support, possibility to make the 
coating using all metallic materials with electro-
conductive proprieties, the simplicity of the process 
and low energy costs. Electric-spark alloying is very 
simple, and the size of the needed machine is small 
and reliable.  
The pollution effect is low using these 
unconventional technologies, and no toxic composites 
are used (like cyanide).   
 
2. Methodology 
 
Vibrated electrode method belongs to the same 
category of coatings that uses electric arc.  Hardening 
with electric sparks principle consists in that in 
electric sparks discharge, with pulsating recovered 
current, polar transport of electrode material takes 
place (anode) on part surface (cathode). This material 
(electrode) alloys the part surface by chemical mixing 
with atomic nitrogen from the environment and the 
carbon from the part surface. A diffusion hardened 
layer is formed with high ware resistance. In the 
superficial layer, complex chemical compositions are 
formed: nitrides, carbon-nitrides, very stable carbides 
and quenched layers. Electric spark hardening of parts 
and tools submissive to wear, is done by contact, with 
manual vibrator. The process starts by approaching 
the anode with the cathode. After penetrating the 
space between the electrodes and the beginning of 
discharge channel (plasmatic stage of discharge), 
from the part surface vaporization and elimination of 
liquid stage begin. Under the electro ionic action of 
plasma and vapour currents and the liquid stage, on 
the electrodes, in the energetic discharge areas melted 
material micro-volumes are formed. As energetic 
discharge (electro-spark processing specific) develops 
a vapour splash and a liquid stage formed take place 
and lead to pressure increase between the electrodes.  
The high temperature generated by the spark 
leads to partial melting and mixing of the electrode 
material with the surface material.  
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FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
N0. 1 – 2009, ISSN 1453 – 083X 
 
 
Between two sparks, the low quantity of melted 
metal solidifies, developing a protective layer.   
 
3. Results and discussion 
 
The paper, in this context, has the following 
general objectives: 
- Titan coating study as interface wolfram as 
exterior layer;  
- Layer thickness analysis; 
- Coating layer crack analysis;  
Hardening by impulse discharge can be used 
with benefice effect on pumps for desalinization of 
water, which are working in high ware conditions, for 
increasing their lifetime.   
For the experiment was used grey ferito-perlitic 
cast-iron (fig. 1) whose chemical composition is 
presented in table 1. This composition is determined 
with Foundry Master Spectrometer machine.   
Tests were made with Elitron 22 machine and 
titan electrode as interface with wolfram as exterior 
layer was used. 
 
Table 1. Basic material chemical composition, % 
 
C Si Mn P S Cr Ni Cu Mo 
3.97 2.87 0.25 0.06 0.07 0.28 0.126 0.17 0.03 
 
          
 
Fig. 1. Basic material microstructure  
 
Ti as interface and W exterior layer coatings are 
good from metallurgic point of view, and have high 
accuracy.  
In fig. 2 taken with electronic scanning method, 
we can see that heterogeneous coatings with Ti 
interface and W exterior layer. These have a soft look, 
with few asperity and bumps, with small melted 
material drops welded to the exterior. These are the 
wolfram electro erosion micro alloying 
characteristics.
     
a) b) 
Fig. 2. a), b) BSE pictures (back scattered electron) and SE ( scanning electron) for  
Ti interface and W exterior layer coating on ferito-perlitic cast-iron.
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Exterior layer is showing soft cracks and small 
adherence areas. Titan was used as transition layer 
between ferrito-perlitic support and the wolfram layer.  
 
 
Fig. 3. Layer thickness 
 
The intermediary layer levels the coating 
because of a good adherence and a constant thickness 
and a good plasticity at high temperatures. At the 
second layer deposition a low roughness exterior is 
formed (fig. 3).  
Titanium is an important presence not only in 
the interface but on the exterior thanks to metal bath 
dynamics made at double coating, demonstrated by 
the appearance of areas with titanium mainly at 
coating edge drops. Studying the elements 
distribution, a smooth and uniform distribution is 
observed of titanium and wolfram elements, 
mentioning that wolfram agglomerations atoms are 
found mainly in the middle of the drop and on micro-
adherence like plucks, of electrode micro-cracks 
partially melted and welded on the exterior layer. 
From the coating layer thickness point of view it 
is quite important to be between 42,06 – 63,09 µm.  
Because wolfram gives more good results, it 
burns the part surface producing grooves in the 
material (material loss by vaporization), oxides and 
adherences, observing an irregular surface with high 
roughness and uneven layer. To avoid this 
inconvenience an intermediary titan coating layer on 
grey cast iron matrix, then the wolfram layer which 
doesn’t coat but strongly melts the exterior layer. 
Only accidentally small particles from the wolfram 
electrode lands on the part surface because dynamics. 
Titanium’s main effect is decrease of layer roughness 
and increase surface quality by obtaining the layer 
with few cracks, oxides and bumps.  
Studying the pictures with in line analysis we 
observe titanium presence as a relatively compact 
layer covered with a dispersion of the wolfram layer 
(fig.  4). 
 
 
       
 
Fig. 4. In line analysis of Ti interface coating, and W exterior layer  
 
Inside the fracture the part presents a compact 
layer, adherent and with a basic material 
compatibility, evident by the presence of similarities 
such as fibres and composition between coating and 
ferito-perlitic matrix.   
Titanium presents a good distribution on all 
coating area, evident at in line analysis, when titanium 
percent, on section coating, varies between 15 - 100% 
through the whole layer thickness which varies 
between 30 - 40 µm.  
 
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FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
N0. 1 – 2009, ISSN 1453 – 083X 
 
 
           
 
Fig. 5. Coating layer cracked areas highlighted in pictures taken through  
electronic scanning microscope   
 
Wolfram has a very low percent in section (8 – 
12%) and distributed in the middle area, that is 
justified by the high temperature used for its melting, 
that means it is absent from the alloying bath but as 
accidentally extracted particles from the top of the  
electrode, because of thermo-electrical flux dynamics. 
The same thing is checked by point EDX analysis in 
the coating material, when analyzed areas present a 
titan concentricity of 24.47%, 24.46% and wolfram 
9.91%, 21% (in the measured points).    
 
 
 
Fig. 6. Coating layer crack point analysis.    
 
 
 
 
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FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
N0. 1 – 2009, ISSN 1453 – 083X 
 
 
Table 2. Point analysis of chemical composition inside Crack area, % 
 
Element AN Net [wt.%] [norm. wt.%] 
[norm. 
at.%] Error in % 
Oxygen 8 2523 39.50027 36.58712 62.08326 64.40004 
Titanium 22 67228 26.42008 24.47159 13.8758 0.757145 
Iron 26 44113 25.37151 23.50035 11.42417 0.678102 
Tungsten 74 9297 10.70124 9.912021 1.463688 0.311983 
Nitrogen 7 1265 4.505784 4.173481 8.089333 7.442224 
Carbon 6 2040 1.46337 1.355446 3.063748 0.300936 
 
4. Conclusions 
 
1. Ferrito-perlitic cast-iron hardening, with titan 
electrode as interface and W as exterior layer using 
vibrator electrode method, is done, mainly, because of 
hard white cast-iron layer developing, superficial 
quenching specific.   
2. Hardened layer thickness, by Ti interface and 
W exterior layer coating, has a thickness between 31 
μm and 63 μm.  
3. Inside the fracture we observe that the 
hardened layer has a good coherence with basic 
matrix. This thing leads to exfoliation absence. 
 
 
 
 
 
 
References 
 
[1]. Alexandru, A. - Teza de doctorat, Contributii privind alierea si 
depunerea superficiala prin scanteiere electrica si influenta 
tratamentelor termice asupra caracteristicilor straturilor obtinute 
ale materialelor metalice, Iasi, 2002 
[2]. Manuela Cristina Perju, Dan Gelu Galusca, Carmen 
Nejneru, Andrei Victor Sandu, Roxana-Gabriela Carabet -
Determinarea caracteristicilor mecanice ale straturilor prin 
depunere, pe suport de fonta, cu electrozi de TiC si W, prin metoda 
electrodului vibrator, Simpozionul national al tinerilor cercetatori 
in domeniul ingineriei materialelor, Bucuresti, 2008, ISSN 978-
606-521-018-9 
[3]. Manuela Perju, Carmen Nejneru , Tudor Răileanu , Mihai 
Axinte, Ion Hopulele - Researches concerning the hardening of 
the grey cast iron through the vibrating electrode method using a 
WC electrode and in combination with TiC and Ti electrode, The 
Annals of “Dunarea de Jos” University of Galati, Fascicle IX. 
Metallurgy And Materials Science N0. 1, 2008, ISSN 1453-083X 
[4]. Vermesan, G.; Vermesan, E.; Jichisan-Matiesan, D.; Cretu, 
A.; Negrea, G.; Vermesan, H.;Vlad, M. - Introducere în ingineria 
suprafeţelor, Editura Dacia, 1999, ISBN 973-35-0922-1. 
 
 
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Analysis of Titanium Interface and Tungsten Exterior Layer Thickness Coated by Vibrator Electrode Method

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Analysis of Titanium Interface and Tungsten Exterior Layer Thickness Coated by Vibrator Electrode Method

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