H. KUANG et al.: MECHANISM OF MULTI-LAYER COMPOSITE COATINGS IN THE ZINC PROCESS ...
997–1003
MECHANISM OF MULTI-LAYER COMPOSITE COATINGS IN THE
ZINC PROCESS OF RECYCLING COATED WC-Co
CEMENTED-CARBIDE SCRAP
MEHANIZEM VE^PLASTNIH KOMPOZITNIH PREMAZOV V
PROCESU CINKANJA ZA RECIKLIRANJE ODPADKOV
OPLA[^ENIH WC-Co KARBIDNIH TRDIN
Hai Kuang1,2, Dunqiang Tan1, Wen He1, Xiaoru Wang1, Jun Zhong1,
Huajian Wang1, Chenghui Yang1
1Nanchang University, School of Materials Science and Engineering, Nanchang 330031, China
2Jiangxi Science and Technology Normal University, School of Materials and Electromechanics, Nanchang 330038, China
tdunqiang@ncu.edu.cn
Prejem rokopisa – received: 2017-04-30; sprejem za objavo – accepted for publication: 2017-06-16
doi:10.17222/mit.2017.049
The mechanism of a coating is crucial for the zinc-process parameters and zinc-recycled WC powders as well as the subsequent
production. The mechanism of a multi-layer composite coating in a zinc process was discussed and the coating with recycled
WC powders was studied. The results demonstrated that the coating created a barrier in the zinc process, resulting in a longer
recycling time for the coated hard-metal scrap. Furthermore, cracks that appeared due to different thermal-expansion
coefficients of the materials were the main reason for the breakdown of the coating, rather than the reaction or the dissolution;
and the molten zinc mainly went through cracks. Additionally, the coating elements and fragments were found in the recycled
WC powders.
Keywords: zinc process, coated cemented-carbide scrap, recycle, cracks
Na~in in vrsta opla{~enja WC-Co karbidne trdine je klju~nega pomena za procesne parametre cinkanja za s cinkom reciklirane
WC-prahove, kot tudi za njihovo nadaljnjo obdelavo. V pri~ujo~i raziskavi so avtorji raziskovali vpliv opla{~enja karbidne
trdine na proces cinkanja za recikla`o WC-prahov. Rezultati so pokazali, da ve~slojna prevleka ustvari oviro v procesu cinkanja,
kar posledi~no podalj{a ~as recikliranja opla{~enih karbidnih trdin. Poleg tega so glavni razlog za pokanje prevlek razli~ni
koeficienti toplotnega raztezanja materialov in namesto njihovega raztapljanja poteka infiltracija raztaljenega cinka skozi
razpoke do karbidne trdine. Tako so v recikliranem WC prahu na{li tudi elemente in delce trdih prevlek.
Klju~ne besede: cinkanje, odpadki opla{~enih karbidnih trdin, recikliranje, razpoke
1 INTRODUCTION
The coated WC-Co cemented-carbide is winning an
increasing market share for its good performance.1–4
Accordingly, the quantity of coated WC-Co hard-metal
scrap is also increasing. However, Tungsten, its main
component, has very limited resources worldwide and
encounters a supply risk.5,6 Therefore, the recycling of
WC from coated cemented-carbide scrap is imperative
for stringent environmental controls and resource-con-
servation policies.
In recent years, the recycling of the coated WC-Co
cemented-carbide scrap has attracted more and more
attention. To our knowledge, only a few articles reported
it and they mainly focused on the process of recycling.
WC-Co hard-metal scrap was reported to be treated
directly in sulphuric acid or after removing the coatings
by oxidation.7,8 However, both of the above would cause
serious health and environmental problems. In research,
recycled WC powders were obtained with a treatment at
a high temperature and a crushing procedure, but the
performance was not as good as for virgin powders and
needed to be improved.9,10 In our previous studies,
removing the coating with a chemical method was
researched,11 but it was difficult to remove the coating
completely. Therefore, it is essential to promote a
high-efficiency procedure for recycling the WC powders
from the coated WC-Co cemented-carbide scrap.
The zinc process, which is one of the most extensiv-
ely used methods for recovering WC powders, was
proved to be efficient and economical.12–14 In the zinc
process, the molten zinc reacts with Co, and sub-
sequently the bond between the binder and the tungsten
carbide grains is broken. As a result, the produced
porous tungsten carbide product can be easily mecha-
nically broken. K. Stjernberg15 thought that the coating
was a hazard for recycling the coated WC-Co cemented-
carbide scrap in the zinc process, as it created a barrier to
the reaction. Moreover, the mechanism of coating in the
zinc process was not clarified. To our knowledge, no
scientific literature reported on the mechanism of coat-
ings, the reason for the breakdown of the coated hard
metal in the zinc process, and the place where the
coating element leaves at the end. All of the three areas
Materiali in tehnologije / Materials and technology 51 (2017) 6, 997–1003 997
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
UDK 62-761:669.58:67.017 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 51(6)997(2017)
mentioned are crucial to the quality of the recycled WC
powders and the process parameters include the
recycling time, zinc content and temperature, even in the
industrial production of subsequently recycled powders.
Therefore, an investigation of the mechanism of the coat-
ing in a zinc process becomes significant for tungsten
recycling and environmental protection.
In this research, the zinc process was adopted to
recycle multi-layer, composite, coated WC-Co hard-
metal tool-tip scraps, aiming to provide an understanding
of the mechanism of the coatings. The microstructure
and mechanism of the coatings were studied; the mate-
rial interactions among the coatings, zinc and Co were
analyzed, and the failure mechanism was also discussed.
This work intended to provide valuable information
about an efficient zinc process for recycling coated
WC-Co cemented-carbide scrap.
2 EXPERIMENTAL PART
2.1 Materials
The multi-layer composite coated WC-Co cemen-
ted-carbide scrap employed for this study was a turning
insert after sufficient usage, purchased from a scrap
merchant. The dimensions of the sample were 12 mm ×
12 mm × 5 mm and its weigh was about 9 g. The che-
mical composition of the sample mainly included WC
and the Co binder (7.41 % mass fraction) and also some
other rare elements such as Ta, Nb and Ti. Four flanks of
the sample were coated with titanium carbonitride
(TiCN)/aluminum oxide (Al2O3)/titanium nitride (TiN)
through the chemical-vapor-deposition (CVD) method,
while the other two faces were covered with TiCN (dark
grey)/Al2O3 (light grey), as shown in Figure 1a. The top
coating, TiN, was removed to reduce the stress. Zinc
blocks were cut from zinc ingots with a purity of 99.95 %
in order to be conveniently placed in graphite crucibles.
2.2 Experiment procedure
The multi-layer, composite, coated WC-Co cemen-
ted-carbide scrap was first treated with an ultrasonic
cleaner using acetone and ethanol, and the sample was
then packed into high-purity graphite crucibles along
with pure zinc blocks. The crucible was a hollow
cylinder with a 5-mm inner diameter and 40-mm height.
The weight of zinc blocks depends on the Co content in
the industry and the preferred weight ratio of zinc to
cobalt is usually within a range of about 20:1 to 15:1.16
In our study, the weight ratio of zinc to cobalt was about
50:1. The excessive weight of zinc aimed to research the
corrosion behavior in detail. Lids were put on crucibles,
and these were then placed in an electric furnace
(Yifeng, SX2-4-10). A standard thermocouple was used
to check the temperature of the furnace, which was
heated from room temperature to 880 °C. A sample and
zinc ingots were isothermally maintained at 880 °C. The
tips were immersed into molten zinc since the zinc
blocks melted at 419.5 °C. The coated hard-metals were
treated for (2, 6, 9 and 15) h, while the uncoated samples
were treated for (2, 6 and 9) h during the zinc process.
Subsequently, the sample was naturally cooled down to
room temperature and then cut using wire-electrode
cutting to conveniently examine the interface. In addi-
tion, the samples treated with the zinc process for 15 h
were placed in a baker containing a 2 mol/L hydrochloric
acid aqueous solution. Zn and Co were dissolved in the
solution, while WC was deposited on the bottom as a
solid. After being washed with water, the solution was
filtrated and dried to obtain the WC powder.
The WC-Co cemented-carbide scrap in the zinc pro-
cess from the photographs was examined using an
optical microscope. The micromorphologies were inves-
tigated with a field-emission scanning electron micro-
scope (FESEM), whilst the element compositions of the
samples were characterized using energy-dispersive
X-ray spectroscopy (EDS). The inductively-coupled-
plasma method (ICP, optima 5300DV) was employed to
test the element content of the recycled powder.
Recycled products of the WC–Co scrap samples were
identified using an X-ray diffractometer (XRD;
PANalytical, EMPYREAN).
H. KUANG et al.: MECHANISM OF MULTI-LAYER COMPOSITE COATINGS IN THE ZINC PROCESS ...
998 Materiali in tehnologije / Materials and technology 51 (2017) 6, 997–1003
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 1: SEM images of multi-layer composite coated WC-Co
cemented-carbide scrap: a) cross-section, b) surface
3 RESULTS AND DISCUSSION
3.1 Multi-layer composite coated WC-Co cemented-
carbide scrap in the zinc process
The macrostructures of the multi-layer, composite,
coated WC-Co cemented-carbide scrap treated with the
zinc process were characterized. Figure 2 includes
cross-section images of the WC-Co cemented carbides in
the zinc process after cooling down and solidification.
Obvious changes can be observed. As shown in Fig-
ure 2a, a few cracks could be clearly observed in the
sample having been treated at 880 °C for 2 h. Zinc got
into the samples mainly through the cracks. The volume
of scrap expanded and more cracks were found after
having been treated for 9 h (as shown in Figure 2b). As
shown in Figure 2c, the substrate was dispersed in zinc
after a treatment for 15 h. Figures 2d and 2e show the
uncoated WC-Co cemented-carbides scrap. It can be
found that the samples could not even maintain the
square shape after the 2-h treatment and the WC
particles were distributed in zinc only after the 9-h
treatment. The results demonstrated that the coating was
a barrier in the zinc process. More time was required to
recover the WC powders from the coated WC-Co
cemented-carbide scrap.
3.2 Characterization of the recycled powders
Figure 3 shows the results for the recycled WC
particles. The substrate of the coated sample treated with
the zinc process for 15 h was characterized for compa-
rison. As seen in Figure 3b, the substrate (WC) was
dispersed in zinc, revealing that the coating was broken
and Zn completely reacted with Co. It can be observed
that the substrate was porous and loose, and can be easily
broken down mechanically.17 So, recycling the coated
WC-Co cemented-carbide scrap during the zinc process
was feasible, though the coating created a barrier to the
reaction. The recycled WC powders obtained in the
present study can be seen in Figure 3. It can be seen that
the coating was found among the WC particles. EDS
results show the Al element is in the powders recycled
from the coated scrap; but this element could not be
found in the powders obtained from the uncoated
samples, as shown in Figure 3d. However, only WC was
found with the XRD (Figure 3f). The amount of Al in
the recycled powders was only 78 mg/kg, which was
difficult to detect with the XRD analysis.
H. KUANG et al.: MECHANISM OF MULTI-LAYER COMPOSITE COATINGS IN THE ZINC PROCESS ...
Materiali in tehnologije / Materials and technology 51 (2017) 6, 997–1003 999
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 2: Photographs of coated and uncoated WC-Co cemented-
carbide scraps in the zinc process: a) coated sample treated for 2 h,
b) coated sample treated for 9 h, c) coated sample treated for 15 h, d)
uncoated sample treated for 2 h, e) uncoated sample treated for 9 h
Figure 3: Results for recycled WC powders: a) photograph of
recycled WC powders from coated samples, b) cross-section of WC
particles in the substrate of the coated sample in the zinc process for
15 h, c) SEM image and EDS result for the recycled WC powders of
coated samples, d) SEM image and EDS result for the recycled WC
powders of uncoated samples, e) XRD result
mentioned are crucial to the quality of the recycled WC
powders and the process parameters include the
recycling time, zinc content and temperature, even in the
industrial production of subsequently recycled powders.
Therefore, an investigation of the mechanism of the coat-
ing in a zinc process becomes significant for tungsten
recycling and environmental protection.
In this research, the zinc process was adopted to
recycle multi-layer, composite, coated WC-Co hard-
metal tool-tip scraps, aiming to provide an understanding
of the mechanism of the coatings. The microstructure
and mechanism of the coatings were studied; the mate-
rial interactions among the coatings, zinc and Co were
analyzed, and the failure mechanism was also discussed.
This work intended to provide valuable information
about an efficient zinc process for recycling coated
WC-Co cemented-carbide scrap.
2 EXPERIMENTAL PART
2.1 Materials
The multi-layer composite coated WC-Co cemen-
ted-carbide scrap employed for this study was a turning
insert after sufficient usage, purchased from a scrap
merchant. The dimensions of the sample were 12 mm ×
12 mm × 5 mm and its weigh was about 9 g. The che-
mical composition of the sample mainly included WC
and the Co binder (7.41 % mass fraction) and also some
other rare elements such as Ta, Nb and Ti. Four flanks of
the sample were coated with titanium carbonitride
(TiCN)/aluminum oxide (Al2O3)/titanium nitride (TiN)
through the chemical-vapor-deposition (CVD) method,
while the other two faces were covered with TiCN (dark
grey)/Al2O3 (light grey), as shown in Figure 1a. The top
coating, TiN, was removed to reduce the stress. Zinc
blocks were cut from zinc ingots with a purity of 99.95 %
in order to be conveniently placed in graphite crucibles.
2.2 Experiment procedure
The multi-layer, composite, coated WC-Co cemen-
ted-carbide scrap was first treated with an ultrasonic
cleaner using acetone and ethanol, and the sample was
then packed into high-purity graphite crucibles along
with pure zinc blocks. The crucible was a hollow
cylinder with a 5-mm inner diameter and 40-mm height.
The weight of zinc blocks depends on the Co content in
the industry and the preferred weight ratio of zinc to
cobalt is usually within a range of about 20:1 to 15:1.16
In our study, the weight ratio of zinc to cobalt was about
50:1. The excessive weight of zinc aimed to research the
corrosion behavior in detail. Lids were put on crucibles,
and these were then placed in an electric furnace
(Yifeng, SX2-4-10). A standard thermocouple was used
to check the temperature of the furnace, which was
heated from room temperature to 880 °C. A sample and
zinc ingots were isothermally maintained at 880 °C. The
tips were immersed into molten zinc since the zinc
blocks melted at 419.5 °C. The coated hard-metals were
treated for (2, 6, 9 and 15) h, while the uncoated samples
were treated for (2, 6 and 9) h during the zinc process.
Subsequently, the sample was naturally cooled down to
room temperature and then cut using wire-electrode
cutting to conveniently examine the interface. In addi-
tion, the samples treated with the zinc process for 15 h
were placed in a baker containing a 2 mol/L hydrochloric
acid aqueous solution. Zn and Co were dissolved in the
solution, while WC was deposited on the bottom as a
solid. After being washed with water, the solution was
filtrated and dried to obtain the WC powder.
The WC-Co cemented-carbide scrap in the zinc pro-
cess from the photographs was examined using an
optical microscope. The micromorphologies were inves-
tigated with a field-emission scanning electron micro-
scope (FESEM), whilst the element compositions of the
samples were characterized using energy-dispersive
X-ray spectroscopy (EDS). The inductively-coupled-
plasma method (ICP, optima 5300DV) was employed to
test the element content of the recycled powder.
Recycled products of the WC–Co scrap samples were
identified using an X-ray diffractometer (XRD;
PANalytical, EMPYREAN).
H. KUANG et al.: MECHANISM OF MULTI-LAYER COMPOSITE COATINGS IN THE ZINC PROCESS ...
998 Materiali in tehnologije / Materials and technology 51 (2017) 6, 997–1003
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 1: SEM images of multi-layer composite coated WC-Co
cemented-carbide scrap: a) cross-section, b) surface
3 RESULTS AND DISCUSSION
3.1 Multi-layer composite coated WC-Co cemented-
carbide scrap in the zinc process
The macrostructures of the multi-layer, composite,
coated WC-Co cemented-carbide scrap treated with the
zinc process were characterized. Figure 2 includes
cross-section images of the WC-Co cemented carbides in
the zinc process after cooling down and solidification.
Obvious changes can be observed. As shown in Fig-
ure 2a, a few cracks could be clearly observed in the
sample having been treated at 880 °C for 2 h. Zinc got
into the samples mainly through the cracks. The volume
of scrap expanded and more cracks were found after
having been treated for 9 h (as shown in Figure 2b). As
shown in Figure 2c, the substrate was dispersed in zinc
after a treatment for 15 h. Figures 2d and 2e show the
uncoated WC-Co cemented-carbides scrap. It can be
found that the samples could not even maintain the
square shape after the 2-h treatment and the WC
particles were distributed in zinc only after the 9-h
treatment. The results demonstrated that the coating was
a barrier in the zinc process. More time was required to
recover the WC powders from the coated WC-Co
cemented-carbide scrap.
3.2 Characterization of the recycled powders
Figure 3 shows the results for the recycled WC
particles. The substrate of the coated sample treated with
the zinc process for 15 h was characterized for compa-
rison. As seen in Figure 3b, the substrate (WC) was
dispersed in zinc, revealing that the coating was broken
and Zn completely reacted with Co. It can be observed
that the substrate was porous and loose, and can be easily
broken down mechanically.17 So, recycling the coated
WC-Co cemented-carbide scrap during the zinc process
was feasible, though the coating created a barrier to the
reaction. The recycled WC powders obtained in the
present study can be seen in Figure 3. It can be seen that
the coating was found among the WC particles. EDS
results show the Al element is in the powders recycled
from the coated scrap; but this element could not be
found in the powders obtained from the uncoated
samples, as shown in Figure 3d. However, only WC was
found with the XRD (Figure 3f). The amount of Al in
the recycled powders was only 78 mg/kg, which was
difficult to detect with the XRD analysis.
H. KUANG et al.: MECHANISM OF MULTI-LAYER COMPOSITE COATINGS IN THE ZINC PROCESS ...
Materiali in tehnologije / Materials and technology 51 (2017) 6, 997–1003 999
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 2: Photographs of coated and uncoated WC-Co cemented-
carbide scraps in the zinc process: a) coated sample treated for 2 h,
b) coated sample treated for 9 h, c) coated sample treated for 15 h, d)
uncoated sample treated for 2 h, e) uncoated sample treated for 9 h
Figure 3: Results for recycled WC powders: a) photograph of
recycled WC powders from coated samples, b) cross-section of WC
particles in the substrate of the coated sample in the zinc process for
15 h, c) SEM image and EDS result for the recycled WC powders of
coated samples, d) SEM image and EDS result for the recycled WC
powders of uncoated samples, e) XRD result
3.3 Material interactions
3.3.1 Chemical reactions among the coatings, Zn and
Co
When the molten zinc is in contact with TiCN /Al2O3,
these are possible reactions:
3Zn+Al2O3  2Al+3ZnO (1)
Zn+TiCN  TiC +ZnN (2)
9Co +4Al2O3  3Co3O4+8Al (3)
TiCN+Co  Co3N+TiC (4)
The thermodynamic parameters are calculated and
the standard free-energy change of the equations above
are all over zero (G>0). According to the analysis of
the thermodynamics, Al2O3 and TiCN could not react
with Zn or Co on this condition. This is consistent with
the fact that Al2O3 is usually used to be the anti-corro-
sion material for the zinc corrosion.18 The chemical
reaction is not the main factor for the failure of the
coated WC-Co cemented-carbide scrap in the zinc pro-
cess.
3.3.2 Dissolution and diffusion
The molten-zinc corrosion occurs together with the
physical effect, not a general chemical reaction, and the
physical effect leads to the failure of the material. The
most important ways are dissolution and diffusion.19–21
For a better understanding of the mechanism, the ele-
ment mapping of the sample in the zinc process was
further studied, as shown in Figure 4. It can be seen that
Co was distributed in the zinc-enrichment area due to the
fact that Zn reacts with Co. But only some Co could be
found at the position of the coatings. Moreover, most
coating elements, like Al and Ti, were distributed along
the coating location, revealing that coatings Al2O3 and
TiCN could not dissolve or diffuse much in the molten
zinc and Co. Therefore, the physical effect of dissolution
and diffusion was not the main reason for the breaking
down of the multilayer, composite, coated WC-Co ce-
mented-carbide scrap in the zinc process. Near the WC
particles, it can be seen that there are a few Ti particles,
which were contained in the substrate of the tip.
3.3.3 Pits and cracks
Figures 5 and 6 show the surface and cross-section
images of the multilayer, composite, coated WC-Co
cemented-carbide scrap in the zinc process for different
times. As seen in Figure 5a, the zinc residue on the
surface of the coating was in the shape of a sphere,
demonstrating that Al2O3 is not well wetted by zinc,
which can delay the penetration of molten zinc into the
substrate.22 Previous researches19,23 revealed that the
corrosion of the materials poorly wetted by zinc was
caused by surface defects, usually pits and cracks. They
could provide preferential paths for transporting the
molten zinc to the coatings and the substrate. Therefore,
defects are vulnerable to molten zinc.
In the present study, the multi-layer, composite,
coated WC-Co cemented-carbide scrap was worn out. As
seen in Figure 1, the localized areas of the coating began
to disintegrate, especially at the corners and flanks.24,25 A
number of defects were observed on the surfaces of the
samples. Pits could be generated during the deposition of
coatings or appear during the cutting of alloys.23 Most
pits were concentrated on damaged local edges and cor-
ners. In this study, the pits provided the paths for trans-
porting the molten zinc. The molten zinc could penetrate
inwards via intergranular boundaries of the coatings
(Figure 5a). Therefore, the pits were the reason for the
failure of the coatings. Pits in coatings are inversely
proportional to the coating resistance, i.e., a lot of pits
with a larger size lead to an easier coating breakdown.26
It can be seen from Figures 5 and 6 that not much zinc
H. KUANG et al.: MECHANISM OF MULTI-LAYER COMPOSITE COATINGS IN THE ZINC PROCESS ...
1000 Materiali in tehnologije / Materials and technology 51 (2017) 6, 997–1003
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 4: Element mapping for multilayer, composite, coated, WC-Co
cemented-carbide scrap in zinc process
Figure 5: Surface SEM images of multi-layer, composite, coated
WC-Co cemented-carbide scrap in zinc process for different times:
a) 2 h, b) 6 h, c) 9 h, d) 15 h
got into the samples through the pits as the coating
created a barrier.
Most of zinc got into the samples through cracks, as
shown in Figures 5 and 6. When coatings are deposited,
cracks are created due to the lattice mismatch. As shown
in Figures 6a to 6d, the molten zinc reached the sub-
strate mainly by penetrating the cracks. At the early
stage, pits also lead to the formation of microcracks with
the increasing treating time. Most of these cracks were
generated during the cutting or heating of the metals due
to a difference between the thermal-expansion coeffi-
cients of the substrate and coating materials (Table 1).27
Stress was the main reason for an increased number of
larger cracks.28 Furthermore, the exfoliation of the coat-
ings contributed to an increased crack coalescence.29
Table 1: Thermal-expansion coefficients of materials
Material TiN Al2O3 TiCN WC Zn
Thermal-expansion
coefficient (10–6K) 9.35 9.0 7.8 4.3 30.2
Zinc went through pits and microcracks at the early
stage (Figures 5a and 6a). Then the number of pits
increased and they became deeper and larger with the
increasing treatment time; the cracks also increased due
to the expansion. The converging of microcracks also led
to wide cracks. It can be seen that at the early stage, a
crack (Figure 5a) has a width of less than 5 μm, and at
the last stage, a wide crack (Figure 5d) has a width of
more than 230 μm. This led to a localized breakdown of
a coating. Several coatings even became detached from
the substrate with the increasing treating time, as shown
in Figures 6e and 6f. During the last stage, the samples
were dispersed. Most WC particles were separated in
zinc due to the dissolution of the Co binder. Localized
breakdowns of the coatings and substrates can be ob-
served. Some coatings were torn into pieces and deviated
from the original position. Several coating elements can
be found among the WC particles (Figure 6e) or in the
zinc-enriched region (Figure 6f). This indicates that the
molten zinc mainly got in through the cracks, and it was
the main mechanism of the failure coatings, which is al-
so demonstrated with the element mapping in Figure 4.
The result is consistent with the conclusion that the
formation and extension of cracks is the main reason for
the breakdown of coated carbide tools in the zinc pro-
cess.30
In order to further study the corrosion behavior of the
multi-layer, composite coating, recycled WC powders
were characterized with SEM as shown in Figure 7.
Coating fragments flaking off were found. Some were
tightly bound with the WC particles (Figure 7a) and
others were on their own among the WC particles. That
is in good agreement with the result from Figure 6.
H. KUANG et al.: MECHANISM OF MULTI-LAYER COMPOSITE COATINGS IN THE ZINC PROCESS ...
Materiali in tehnologije / Materials and technology 51 (2017) 6, 997–1003 1001
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 7: SEM images of the coatings in recycled WC powders
Figure 6: Cross-section SEM images of multi-layer, composite,
coated WC-Co cemented-carbide scrap in zinc process for different
times: a) 2 h, b) 6 h, c) 9 h, d) 15 h, e) coatings distributed among WC
particles in the zinc process of 15 h, f) coatings distributed in the
zinc-enriched area in the zinc process of 15 h
3.3 Material interactions
3.3.1 Chemical reactions among the coatings, Zn and
Co
When the molten zinc is in contact with TiCN /Al2O3,
these are possible reactions:
3Zn+Al2O3  2Al+3ZnO (1)
Zn+TiCN  TiC +ZnN (2)
9Co +4Al2O3  3Co3O4+8Al (3)
TiCN+Co  Co3N+TiC (4)
The thermodynamic parameters are calculated and
the standard free-energy change of the equations above
are all over zero (G>0). According to the analysis of
the thermodynamics, Al2O3 and TiCN could not react
with Zn or Co on this condition. This is consistent with
the fact that Al2O3 is usually used to be the anti-corro-
sion material for the zinc corrosion.18 The chemical
reaction is not the main factor for the failure of the
coated WC-Co cemented-carbide scrap in the zinc pro-
cess.
3.3.2 Dissolution and diffusion
The molten-zinc corrosion occurs together with the
physical effect, not a general chemical reaction, and the
physical effect leads to the failure of the material. The
most important ways are dissolution and diffusion.19–21
For a better understanding of the mechanism, the ele-
ment mapping of the sample in the zinc process was
further studied, as shown in Figure 4. It can be seen that
Co was distributed in the zinc-enrichment area due to the
fact that Zn reacts with Co. But only some Co could be
found at the position of the coatings. Moreover, most
coating elements, like Al and Ti, were distributed along
the coating location, revealing that coatings Al2O3 and
TiCN could not dissolve or diffuse much in the molten
zinc and Co. Therefore, the physical effect of dissolution
and diffusion was not the main reason for the breaking
down of the multilayer, composite, coated WC-Co ce-
mented-carbide scrap in the zinc process. Near the WC
particles, it can be seen that there are a few Ti particles,
which were contained in the substrate of the tip.
3.3.3 Pits and cracks
Figures 5 and 6 show the surface and cross-section
images of the multilayer, composite, coated WC-Co
cemented-carbide scrap in the zinc process for different
times. As seen in Figure 5a, the zinc residue on the
surface of the coating was in the shape of a sphere,
demonstrating that Al2O3 is not well wetted by zinc,
which can delay the penetration of molten zinc into the
substrate.22 Previous researches19,23 revealed that the
corrosion of the materials poorly wetted by zinc was
caused by surface defects, usually pits and cracks. They
could provide preferential paths for transporting the
molten zinc to the coatings and the substrate. Therefore,
defects are vulnerable to molten zinc.
In the present study, the multi-layer, composite,
coated WC-Co cemented-carbide scrap was worn out. As
seen in Figure 1, the localized areas of the coating began
to disintegrate, especially at the corners and flanks.24,25 A
number of defects were observed on the surfaces of the
samples. Pits could be generated during the deposition of
coatings or appear during the cutting of alloys.23 Most
pits were concentrated on damaged local edges and cor-
ners. In this study, the pits provided the paths for trans-
porting the molten zinc. The molten zinc could penetrate
inwards via intergranular boundaries of the coatings
(Figure 5a). Therefore, the pits were the reason for the
failure of the coatings. Pits in coatings are inversely
proportional to the coating resistance, i.e., a lot of pits
with a larger size lead to an easier coating breakdown.26
It can be seen from Figures 5 and 6 that not much zinc
H. KUANG et al.: MECHANISM OF MULTI-LAYER COMPOSITE COATINGS IN THE ZINC PROCESS ...
1000 Materiali in tehnologije / Materials and technology 51 (2017) 6, 997–1003
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 4: Element mapping for multilayer, composite, coated, WC-Co
cemented-carbide scrap in zinc process
Figure 5: Surface SEM images of multi-layer, composite, coated
WC-Co cemented-carbide scrap in zinc process for different times:
a) 2 h, b) 6 h, c) 9 h, d) 15 h
got into the samples through the pits as the coating
created a barrier.
Most of zinc got into the samples through cracks, as
shown in Figures 5 and 6. When coatings are deposited,
cracks are created due to the lattice mismatch. As shown
in Figures 6a to 6d, the molten zinc reached the sub-
strate mainly by penetrating the cracks. At the early
stage, pits also lead to the formation of microcracks with
the increasing treating time. Most of these cracks were
generated during the cutting or heating of the metals due
to a difference between the thermal-expansion coeffi-
cients of the substrate and coating materials (Table 1).27
Stress was the main reason for an increased number of
larger cracks.28 Furthermore, the exfoliation of the coat-
ings contributed to an increased crack coalescence.29
Table 1: Thermal-expansion coefficients of materials
Material TiN Al2O3 TiCN WC Zn
Thermal-expansion
coefficient (10–6K) 9.35 9.0 7.8 4.3 30.2
Zinc went through pits and microcracks at the early
stage (Figures 5a and 6a). Then the number of pits
increased and they became deeper and larger with the
increasing treatment time; the cracks also increased due
to the expansion. The converging of microcracks also led
to wide cracks. It can be seen that at the early stage, a
crack (Figure 5a) has a width of less than 5 μm, and at
the last stage, a wide crack (Figure 5d) has a width of
more than 230 μm. This led to a localized breakdown of
a coating. Several coatings even became detached from
the substrate with the increasing treating time, as shown
in Figures 6e and 6f. During the last stage, the samples
were dispersed. Most WC particles were separated in
zinc due to the dissolution of the Co binder. Localized
breakdowns of the coatings and substrates can be ob-
served. Some coatings were torn into pieces and deviated
from the original position. Several coating elements can
be found among the WC particles (Figure 6e) or in the
zinc-enriched region (Figure 6f). This indicates that the
molten zinc mainly got in through the cracks, and it was
the main mechanism of the failure coatings, which is al-
so demonstrated with the element mapping in Figure 4.
The result is consistent with the conclusion that the
formation and extension of cracks is the main reason for
the breakdown of coated carbide tools in the zinc pro-
cess.30
In order to further study the corrosion behavior of the
multi-layer, composite coating, recycled WC powders
were characterized with SEM as shown in Figure 7.
Coating fragments flaking off were found. Some were
tightly bound with the WC particles (Figure 7a) and
others were on their own among the WC particles. That
is in good agreement with the result from Figure 6.
H. KUANG et al.: MECHANISM OF MULTI-LAYER COMPOSITE COATINGS IN THE ZINC PROCESS ...
Materiali in tehnologije / Materials and technology 51 (2017) 6, 997–1003 1001
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 7: SEM images of the coatings in recycled WC powders
Figure 6: Cross-section SEM images of multi-layer, composite,
coated WC-Co cemented-carbide scrap in zinc process for different
times: a) 2 h, b) 6 h, c) 9 h, d) 15 h, e) coatings distributed among WC
particles in the zinc process of 15 h, f) coatings distributed in the
zinc-enriched area in the zinc process of 15 h
4 CONCLUSIONS
The mechanism of a coating in a zinc process in-
fluences the properties of the recycled powders, the
recycling process and thus the subsequent industrial
production. In this study, the breakdown of a multi-layer
composite coating was investigated. The results show
that the coating delayed the reaction of Zn and Co in the
zinc process; therefore, a longer time was needed for
recycling coated hard-metal scraps. Both the pits and
cracks were the reason for the failure of the coatings in
the zinc process and zinc got into the samples mainly
through the cracks, most of which appeared due to
different thermal-expansion coefficients of the materials.
After the treatment in the zinc process for 15 h, the
substrate became porous and loose. WC powders were
successfully obtained from the multi-layer, composite,
coated WC-Co cemented-carbide scrap with the zinc
process, and stripped coatings were found in the recycled
WC powders. This investigation can provide some fun-
damental information needed to develop an efficient
recycling method for multi-layer, composite, coated
WC-Co cemented-carbide scrap.
Acknowledgement
This work was supported by the National Natural
Science Foundation of China (51564036 and 50904035),
the National High-Tech R&D Program of China
(2012AA061902) and the National Key Technology
R&D Program of China (2011BAC10B04).
5 REFERENCES
1 L. Y. Zhou, J. T. Ni, Q. H, Study on failure mechanism of the coated
carbide tool, International Journal of Refractory Metals and Hard
Materials, 25 (2007) 1, 1–5, doi:10.1016/j.ijrmhm.2005.10.002
2 G. J. Ma, L. L. Wang, H. X. Gao, J. Zhang, T. Reddyhoff, The fric-
tion coefficient evolution of a TiN coated contact during sliding
wear, Applied Surface Science, 345 (2015), 109–115, doi:10.1016/
j.apsusc.2015.03.156
3 Q. Z. Wang, F. Zhou, X. N. Wang, K. M. Chen, M. L. Wang, T. Qian,
Y. X. Li, Comparison of tribological properties of CrN, TiCN and
TiAlN coatings sliding against SiC balls in water, Applied Surface
Science, 25 (2011), 7813–7820, doi:10.1016/j.apsusc.2011.04.035
4 K. J. Brookes, Hardmetals group studies coatings, Metal Powder Re-
port, 69 (2014) 2, 22–27, doi:10.1016/S0026-0657(14)70080-3
5 T. Yamaguchi, H. Hagino, Y. Michiyama, Sliding Wear Properties of
Ti/TiC Surface Composite Layer Formed by Laser Alloying, Ma-
terials Transactions, 56 (2015) 3, 361–366, doi:10.2320/matertrans.
m2014330
6 T. Ishlda, T. Itakura, H. Morlguchl, A. Ikegaya, Development of
technologies for recycling cemented carbide scrap and reducing
tungsten use in cemented carbide tools, Sei Technical Review, 75
(2012) 75, 38–46
7 W. H. Gu, Y. S. Jeong, K. Kim, J. C. Kim, S. H. Son, S. Kim, Ther-
mal oxidation behavior of WC-Co hard metal machining tool tip
scraps, Journal of Materials Processing Technology, 212 (2012) 6,
1250–1256, doi:10.1016/j.jmatprotec.2012.01.009
8 C. D. Vanderpeel, R. A. Seheithauer, R. G. Warmington, Recovery of
refractory metal values from scrap cemented carbide, US Patent,
4432950 (1984)
9 Z. J. Wu, P. Zhang, J. S. Zeng, Z. Y. Deng, The process of producing
cemented carbide by recycled WC powders, Cemented Carbide, 22
(2005) 3, 170–172, doi:10.3969/j.issn.1003-7292.2005.03.010
10 Z. J. Wu, J. Liu, Research on removing of the coating from the
coated cemented carbide, Non-ferrous metals recycling and utiliza-
tion, 7 (2005) 2, 19–20
11 Y. Liu, D. Q. Tan, D. P. Lu, L. Lei, J. Long, Corrosion behavior in
process of removing TiN coating of waste cemented carbide by che-
mical method, Materials Science and Engineering of Powder
Metallurgy, 18 (2013) 1, 20–25, doi:10.3969/j.issn.1673-0224.2013.
01.006
12 K. J. Brookes, Hardmetals recycling and the environment, Metal
Powder Report, 69 (2014) 5, 24–30, doi:10.1016/S0026-0657(14)
70225-5
13 C. S. Freemantle, N. Sacks, M. Topic, C. A. Pineda-Vargas, PIXE as
a characterization technique in the cutting tool industry, Nuclear
Instruments and Methods in Physics Research Section B: Beam
Interactions with Materials and Atoms, 318 (2014) 1, 168–172,
doi:10.1016/j.nimb.2013.06.044
14 E. Altuncu, F. Ustel, A. Turk, S. Ozturk, G. Erdogan, Cutting-tool
recycling process with the zinc-melt method for obtaining
thermal-spray feedstock powder (WC-Co), Materiali in Tehnologije,
47 (2013) 1, 115–118
15 K. Stjernberg, J. Johnson, Recycling of cemented carbides, Metal
Powder Report, 53 (1998) 12, 40, doi:10.1016/s0026-0657(99)
80135-0
16 P. G. Barnard, A. G. Starliper, H. Kenworthy, Reclamation of refrac-
tory carbides from carbide materials, US Patent 3595484 (1971)
17 J. C. Liu, S. W. Park, S. Nagao, M. Nogi, H. Koga, J. S. Ma, G.
Zhang, K. Suganuma, The role of Zn precipitates and Cl-anions in
pitting corrosion of Sn–Zn solder alloys, Corrosion Science, 92
(2015), 263–271, doi:10.1016/j.corsci.2014.12.014
18 Y. H. Lv, X. S. Wu, Y. F. Liu, Z. J. Wu, Preparation of Al2O3-TiB2
composite ceramic coating and corrosion-resistant property to molten
zinc, China surface engineering, 24 (2011) 4, 30–33, doi:10.3969/
j.issn.1007-9289.2011.04.006
19 X. J. Ren, X. Z. Mei, J. She, J. H. Ma, Materials resistance to liquid
zinc corrosion on surface of sink roll, Journal of Iron and Steel
Research, International, 14 (2007) 5, 130, doi:10.1016/S1006-
706X(08)60066-7
20 M. P. Taylor, J. R. P. Smith, H. E. Evans, Modelling of the inter-
diffusion and oxidation of a multilayered chromia forming thermal
barrier coating, Materials and Corrosion, 68 (2016) 2, 215–219,
doi:10.1002/maco.201508778
21 X. D. Tian, X. P. Guo, Z. P. Sun, J. L. Qu , L. J. Wang, Oxidation
resistance comparison of MoSi2 and B-modified MoSi2 coatings on
pure Mo prepared through pack cementation, Materials and Corro-
sion, 66 (2014) 7, 681–687, doi:10.1002/maco.201407631
22 J. F. Zhang, C. M. Deng, J. B. Song, C. G. Deng, M. Liu, K. S. Zhou,
MoB-CoCr as alternatives to WC-12Co for stainless steel protective
coating and its corrosion behavior in molten zinc, Surface and
Coatings Technology, 235 (2013), 811–818, doi:10.1016/j.surfcoat.
2013.08.052
23 A. A. Matei, I. Pencea, M. Branzei, D. E. Tranca, G. Tepes, C. E.
Sfat, E. Ciovica, A. I. Gherghilescu, G. A. Stanciu, Corrosion
resistance appraisal of TiN, TiCN and TiAlN coatings deposited by
CAE-PVD method on WC–Co cutting tools exposed to artificial sea
water, Applied Surface Science, 358 (2015), 572–578, doi:10.1016/
j.apsusc.2015.08.041
24 J. D. Brassard, D. K. Sarkar, J. Perron, A. Audibert-Hayet, D. Melot,
Nano-micro structured superhydrophobic zinc coating on steel for
prevention of corrosion and ice adhesion, Journal of Colloid and
Interface Science, 447 (2015), 240–247, doi:10.1016/j.jcis.2014.
11.076
25 D. Zhang, B. Shen, F. Sun, Study on tribological behavior and
cutting performance of CVD diamond and DLC films on Co-
cemented tungsten carbide substrates, Applied Surface Science, 256
(2010) 8, 2479–2489, doi:10.1016/j.apsusc.2009.10.092
H. KUANG et al.: MECHANISM OF MULTI-LAYER COMPOSITE COATINGS IN THE ZINC PROCESS ...
1002 Materiali in tehnologije / Materials and technology 51 (2017) 6, 997–1003
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
26 M. Karbasi, M. R. Zamanzad Ghavidel, A. Nekahi, Corrosion
behavior of HVOF sprayed coatings of Ni TiC and Ni (Ti,W)C SHS
produced composite powders and Ni + TiC mixed powder, Materials
and Corrosion, 65 (2012) 5, 485–492, doi:10.1002/maco.201206536
27 A. Matthews, Handbook of hard coatings, Edited by Rointan E.
Bunshah, (2001), 203–205
28 C. Lee, H. Park, J. Yoo, C. Lee, W. C. Woo, S. Park, Residual stress
and crack initiation in laser clad composite layer with Co-based alloy
and WC+NiCr, Applied Surface Science, 345 (2015), 286–294,
doi:10.1016/j.apsusc.2015.03.168
29 H. B. Wang, X. Z. Wang, X. Y. Song, X. M. Liu, X. W. Liu, Sliding
wear behavior of nanostructured WC-Co-Cr coatings, Applied Sur-
face Science, 355 (2015), 453–460, doi:10.1016/j.apsusc.2015.
07.144
30 Y. J. Zheng, Y. X. Leng, X. Xin, Z. Y. Xu, F. Q. Jiang, R. H. Wei, N.
Huang, Evaluation of mechanical properties of Ti(Cr)SiC(O)N
coated cemented carbide tools, Vacuum, 90 (2013) 2, 50–58,
doi:10.1016/j.vacuum.2012.10.002
H. KUANG et al.: MECHANISM OF MULTI-LAYER COMPOSITE COATINGS IN THE ZINC PROCESS ...
Materiali in tehnologije / Materials and technology 51 (2017) 6, 997–1003 1003
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
4 CONCLUSIONS
The mechanism of a coating in a zinc process in-
fluences the properties of the recycled powders, the
recycling process and thus the subsequent industrial
production. In this study, the breakdown of a multi-layer
composite coating was investigated. The results show
that the coating delayed the reaction of Zn and Co in the
zinc process; therefore, a longer time was needed for
recycling coated hard-metal scraps. Both the pits and
cracks were the reason for the failure of the coatings in
the zinc process and zinc got into the samples mainly
through the cracks, most of which appeared due to
different thermal-expansion coefficients of the materials.
After the treatment in the zinc process for 15 h, the
substrate became porous and loose. WC powders were
successfully obtained from the multi-layer, composite,
coated WC-Co cemented-carbide scrap with the zinc
process, and stripped coatings were found in the recycled
WC powders. This investigation can provide some fun-
damental information needed to develop an efficient
recycling method for multi-layer, composite, coated
WC-Co cemented-carbide scrap.
Acknowledgement
This work was supported by the National Natural
Science Foundation of China (51564036 and 50904035),
the National High-Tech R&D Program of China
(2012AA061902) and the National Key Technology
R&D Program of China (2011BAC10B04).
5 REFERENCES
1 L. Y. Zhou, J. T. Ni, Q. H, Study on failure mechanism of the coated
carbide tool, International Journal of Refractory Metals and Hard
Materials, 25 (2007) 1, 1–5, doi:10.1016/j.ijrmhm.2005.10.002
2 G. J. Ma, L. L. Wang, H. X. Gao, J. Zhang, T. Reddyhoff, The fric-
tion coefficient evolution of a TiN coated contact during sliding
wear, Applied Surface Science, 345 (2015), 109–115, doi:10.1016/
j.apsusc.2015.03.156
3 Q. Z. Wang, F. Zhou, X. N. Wang, K. M. Chen, M. L. Wang, T. Qian,
Y. X. Li, Comparison of tribological properties of CrN, TiCN and
TiAlN coatings sliding against SiC balls in water, Applied Surface
Science, 25 (2011), 7813–7820, doi:10.1016/j.apsusc.2011.04.035
4 K. J. Brookes, Hardmetals group studies coatings, Metal Powder Re-
port, 69 (2014) 2, 22–27, doi:10.1016/S0026-0657(14)70080-3
5 T. Yamaguchi, H. Hagino, Y. Michiyama, Sliding Wear Properties of
Ti/TiC Surface Composite Layer Formed by Laser Alloying, Ma-
terials Transactions, 56 (2015) 3, 361–366, doi:10.2320/matertrans.
m2014330
6 T. Ishlda, T. Itakura, H. Morlguchl, A. Ikegaya, Development of
technologies for recycling cemented carbide scrap and reducing
tungsten use in cemented carbide tools, Sei Technical Review, 75
(2012) 75, 38–46
7 W. H. Gu, Y. S. Jeong, K. Kim, J. C. Kim, S. H. Son, S. Kim, Ther-
mal oxidation behavior of WC-Co hard metal machining tool tip
scraps, Journal of Materials Processing Technology, 212 (2012) 6,
1250–1256, doi:10.1016/j.jmatprotec.2012.01.009
8 C. D. Vanderpeel, R. A. Seheithauer, R. G. Warmington, Recovery of
refractory metal values from scrap cemented carbide, US Patent,
4432950 (1984)
9 Z. J. Wu, P. Zhang, J. S. Zeng, Z. Y. Deng, The process of producing
cemented carbide by recycled WC powders, Cemented Carbide, 22
(2005) 3, 170–172, doi:10.3969/j.issn.1003-7292.2005.03.010
10 Z. J. Wu, J. Liu, Research on removing of the coating from the
coated cemented carbide, Non-ferrous metals recycling and utiliza-
tion, 7 (2005) 2, 19–20
11 Y. Liu, D. Q. Tan, D. P. Lu, L. Lei, J. Long, Corrosion behavior in
process of removing TiN coating of waste cemented carbide by che-
mical method, Materials Science and Engineering of Powder
Metallurgy, 18 (2013) 1, 20–25, doi:10.3969/j.issn.1673-0224.2013.
01.006
12 K. J. Brookes, Hardmetals recycling and the environment, Metal
Powder Report, 69 (2014) 5, 24–30, doi:10.1016/S0026-0657(14)
70225-5
13 C. S. Freemantle, N. Sacks, M. Topic, C. A. Pineda-Vargas, PIXE as
a characterization technique in the cutting tool industry, Nuclear
Instruments and Methods in Physics Research Section B: Beam
Interactions with Materials and Atoms, 318 (2014) 1, 168–172,
doi:10.1016/j.nimb.2013.06.044
14 E. Altuncu, F. Ustel, A. Turk, S. Ozturk, G. Erdogan, Cutting-tool
recycling process with the zinc-melt method for obtaining
thermal-spray feedstock powder (WC-Co), Materiali in Tehnologije,
47 (2013) 1, 115–118
15 K. Stjernberg, J. Johnson, Recycling of cemented carbides, Metal
Powder Report, 53 (1998) 12, 40, doi:10.1016/s0026-0657(99)
80135-0
16 P. G. Barnard, A. G. Starliper, H. Kenworthy, Reclamation of refrac-
tory carbides from carbide materials, US Patent 3595484 (1971)
17 J. C. Liu, S. W. Park, S. Nagao, M. Nogi, H. Koga, J. S. Ma, G.
Zhang, K. Suganuma, The role of Zn precipitates and Cl-anions in
pitting corrosion of Sn–Zn solder alloys, Corrosion Science, 92
(2015), 263–271, doi:10.1016/j.corsci.2014.12.014
18 Y. H. Lv, X. S. Wu, Y. F. Liu, Z. J. Wu, Preparation of Al2O3-TiB2
composite ceramic coating and corrosion-resistant property to molten
zinc, China surface engineering, 24 (2011) 4, 30–33, doi:10.3969/
j.issn.1007-9289.2011.04.006
19 X. J. Ren, X. Z. Mei, J. She, J. H. Ma, Materials resistance to liquid
zinc corrosion on surface of sink roll, Journal of Iron and Steel
Research, International, 14 (2007) 5, 130, doi:10.1016/S1006-
706X(08)60066-7
20 M. P. Taylor, J. R. P. Smith, H. E. Evans, Modelling of the inter-
diffusion and oxidation of a multilayered chromia forming thermal
barrier coating, Materials and Corrosion, 68 (2016) 2, 215–219,
doi:10.1002/maco.201508778
21 X. D. Tian, X. P. Guo, Z. P. Sun, J. L. Qu , L. J. Wang, Oxidation
resistance comparison of MoSi2 and B-modified MoSi2 coatings on
pure Mo prepared through pack cementation, Materials and Corro-
sion, 66 (2014) 7, 681–687, doi:10.1002/maco.201407631
22 J. F. Zhang, C. M. Deng, J. B. Song, C. G. Deng, M. Liu, K. S. Zhou,
MoB-CoCr as alternatives to WC-12Co for stainless steel protective
coating and its corrosion behavior in molten zinc, Surface and
Coatings Technology, 235 (2013), 811–818, doi:10.1016/j.surfcoat.
2013.08.052
23 A. A. Matei, I. Pencea, M. Branzei, D. E. Tranca, G. Tepes, C. E.
Sfat, E. Ciovica, A. I. Gherghilescu, G. A. Stanciu, Corrosion
resistance appraisal of TiN, TiCN and TiAlN coatings deposited by
CAE-PVD method on WC–Co cutting tools exposed to artificial sea
water, Applied Surface Science, 358 (2015), 572–578, doi:10.1016/
j.apsusc.2015.08.041
24 J. D. Brassard, D. K. Sarkar, J. Perron, A. Audibert-Hayet, D. Melot,
Nano-micro structured superhydrophobic zinc coating on steel for
prevention of corrosion and ice adhesion, Journal of Colloid and
Interface Science, 447 (2015), 240–247, doi:10.1016/j.jcis.2014.
11.076
25 D. Zhang, B. Shen, F. Sun, Study on tribological behavior and
cutting performance of CVD diamond and DLC films on Co-
cemented tungsten carbide substrates, Applied Surface Science, 256
(2010) 8, 2479–2489, doi:10.1016/j.apsusc.2009.10.092
H. KUANG et al.: MECHANISM OF MULTI-LAYER COMPOSITE COATINGS IN THE ZINC PROCESS ...
1002 Materiali in tehnologije / Materials and technology 51 (2017) 6, 997–1003
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
26 M. Karbasi, M. R. Zamanzad Ghavidel, A. Nekahi, Corrosion
behavior of HVOF sprayed coatings of Ni TiC and Ni (Ti,W)C SHS
produced composite powders and Ni + TiC mixed powder, Materials
and Corrosion, 65 (2012) 5, 485–492, doi:10.1002/maco.201206536
27 A. Matthews, Handbook of hard coatings, Edited by Rointan E.
Bunshah, (2001), 203–205
28 C. Lee, H. Park, J. Yoo, C. Lee, W. C. Woo, S. Park, Residual stress
and crack initiation in laser clad composite layer with Co-based alloy
and WC+NiCr, Applied Surface Science, 345 (2015), 286–294,
doi:10.1016/j.apsusc.2015.03.168
29 H. B. Wang, X. Z. Wang, X. Y. Song, X. M. Liu, X. W. Liu, Sliding
wear behavior of nanostructured WC-Co-Cr coatings, Applied Sur-
face Science, 355 (2015), 453–460, doi:10.1016/j.apsusc.2015.
07.144
30 Y. J. Zheng, Y. X. Leng, X. Xin, Z. Y. Xu, F. Q. Jiang, R. H. Wei, N.
Huang, Evaluation of mechanical properties of Ti(Cr)SiC(O)N
coated cemented carbide tools, Vacuum, 90 (2013) 2, 50–58,
doi:10.1016/j.vacuum.2012.10.002
H. KUANG et al.: MECHANISM OF MULTI-LAYER COMPOSITE COATINGS IN THE ZINC PROCESS ...
Materiali in tehnologije / Materials and technology 51 (2017) 6, 997–1003 1003
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS