ORIGINAL ARTICLE
Investigation of the electrochemical dissolution behavior of tungsten
during electrochemical machining
Chuanyun Zhang
1
&
Yongjun Zhang
1,2
&
Xiaolei Chen
1,2
&
Wei Li
1
&
Guixian Liu
1,2
Received: 9 January 2018 /Accepted: 7 May 2018
#
Springer-Verlag London Ltd., part of Springer Nature 2018
Abstract
With the advantageous properties of a high melting point, high strength at high temperatures, low vapor pressure, and good
thermal conductivity, tungsten is widely used in several advanced industrial applications. Micro structures such as micro holes
and grooves are commonly prepared on the tungsten surface to enhance its heat transfer performance. Electrochemical machining
(ECM) is a promising method of generating micro structures on the metal surface. Typically, an alkaline solution is employed as
an electrolyte during tungsten ECM. Unfortunately, significant stray corrosion commonly occurs on the tungsten surface when
high-concentration alkaline solutions (NaOH > 1 wt.%) are used. However, the machining efficiency decreases sharply when the
concentration is less than 0.5 wt.%. In order to improve machining efficiency and accuracy, this paper proposes a novel mixed
electrolyte consisting of NaClO
3
mixed with a low concentration of NaOH for electrochemical machining of tungsten. The
NaClO
3
is used to increase the conductivity as well as to improve the formation of oxide films on the tungsten surface in order to
avoid stray corrosion. NaOH is used to ensure continuous machining by removing the oxide film in the region being machined.
The influence of the electrolyte composition and concentration on electrochemical dissolution of tungsten is analyzed by
measuring the anode polarization curve and open circuit potential, and an optimized electrolyte with of 10 wt.% NaClO
3
and
0.3 wt.% NaOH is identified. This optimized electrolyte enables generation of micro-through holes with inlet and outlet diameters
of 500 and 410 μm, respectively, using a tube electrode with a diameter of 250 μm. The feed rate of the tool reaches 24 μm/min,
which is 4 times faster than in previous studies.
Keywords Tungsten
.
Mixed electrolyte
.
Passive film
.
Electrochemical drilling
1 Introduction
With excellent properties such as a high energy threshold for
physical sputtering (E
th
~200 eV for D), high melting point,
high-temperature strength, low vapor pressure, and good ther-
mal conductivity [1, 2], tungsten and its alloys are widely used
in the radiating components of xenon lamps, diverters, lim-
iters, and the first wall of the international thermonuclear ex-
perimental reactor [3–5]. Micro structures such as micro holes
and grooves are often added to the surfaces of these tungsten
components to further enhance their heat transfer performance.
Since tungsten is difficult to cut, such micro structures are
typically prepared via laser or electro discharge machining.
However, there are some undesirable effects associated with
processing, such as tool wear, heat-affected zones, spatter, and
recast layers [6–10]. Electrochemical machining (ECM) is
another promising method of generating micro structures on
tungsten surfaces. It works regardless of material hardness and
toughness and produces no heat-affected layer, residual stress-
es, cracks, tool wear, burrs, etc. [11–14].
In ECM, the choice of electrolyte is quite important, as it
directly affects the material dissolution behavior. ECM typi-
cally uses a neutral electrolyte [15–19]. However, due to the
unique dissolution behavior of tungsten, a significant oxide
film (WO
3
) is always formed on the tungsten surface in a
neutral electrolyte. This oxide layer prevents the continuous
dissolution of tungsten [20]. Hence, an alkaline electrolyte is
usually employed in electrochemical machining of tungsten.
* Guixian Liu
gxliu@gdut.edu.cn
1
School of Electro-mechanical Engineering, Guangdong University
of Technology, 510016 Guangzhou, People’sRepublicofChina
2
Guangzhou Key Laboratory of Nontraditional Machining and
Equipment, 510006 Guangzhou, People’s Republic of China
The International Journal of Advanced Manufacturing Technology
https://doi.org/10.1007/s00170-018-2142-3
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