Steel pipe-lined Fe – W
2
B-based composite coating by
centrifugal-Self-propagating high-temperature synthesis process
Saowanee SINGSAROTHAI,
*
,
***
Vishnu RACHPHET
*
,
***
and Sutham NIYOMWAS
**
,
***
,³
*
Department of Mining and Materials Engineering, Faculty of Engineering, Prince of Songkla University,
Hat Yai, Songkhla 90110, Thailand
**
Department of Mechanical Engineering, Faculty of Engineering, Prince of Songkla University, Hat Yai, Songkhla 90110, Thailand
***
Ceramic and Composite Materials Engineering Research Group (CMERG), Center of Excellence in Materials Engineering (CEME),
Faculty of Engineering, Prince of Songkla University, Hat Yai, Songkhla 90110, Thailand
In this study, FeW
2
B-based composite coating on the inner surface of a steel pipe was produced by centrifugal- Self-propagating
high-temperature synthesis (SHS) process. There were FeWO
4
,B
2
O
3
, and Al powders as the major reactants. The effects of
coupled additives X(Fe
2
O
3
Al) of X = 1, 3, and 5 molar ratio on morphology, composition and micro-hardness of the obtained
composite coatings were investigated. The results showed that the system of X = 1 mole was the optimum condition due to its
reasonable smoothness (6.5 ¯m) and hardest (727.90 and 1170.71 HV on alloy and ceramic layers, respectively).
©2016 The Ceramic Society of Japan. All rights reserved.
Key-words : Ceramics, Composites, Coating, Self-propagating high-temperature synthesis (SHS)
[Received May 12, 2016; Accepted August 2, 2016]
1. Introduction
It is well known that ceramic composite materials possess
various outstanding properties including high hardness, high
wear resistance, and high melting point. They are used in many
military and industrial applications such as gun barrels, cutting
tools, and coatings for the transportation of coal cinder, mineral
powder, and oil-water mixture.
1),2)
The coated ceramic layers on
the inner surfaces of pipes, however, were complicated. This is
because the ceramic composite materials require a high energy
and a long period of time to melt themselves prior to the coat-
ing process and hence a high production cost is needed for the
traditional coating processes; high velocity oxygen fuel (HVOF),
plasma spraying, and laser cladding.
3)5)
To overcome this, a
novel alternative technique known as centrifugal-SHS process
has been proposed
6)9)
with the advantages of an inexpensive and
simple operation and a much shorter coating time.
Centrifugal-SHS process is a combination technique of self-
propagating high-temperature synthesis (SHS) and centrifugal
casting. The melted products from the SHS-reaction are separated
by their densities before solidification and formation of the
composite coating layers on the substrate. The ceramic composite
coating is produced in one step that requires little amount of
energy and time. On previous works of O. Odawara
6),7)
syn-
thesized the composite coatings consisted of metal and ceramic
layers from the thermite reaction of 3Fe
3
O
4
+ 8Al ¼ 4Al
2
O
3
+
9Fe. Although the centrifugal-SHS process is easy to use and
requires less production cost, the thermite reaction is too complex
and difficult to control its mechanism. The produced composite
coating was filled with porosity that needs to be improved.
Tungsten borides have been known for their high hardness
and chemical inertness. They have been applied to the industries
which require extremely high hardness, chemical inertness, and
wear resistance, i.e., abrasive media, turbine blades, nozzle of a
gas burner, crucibles and ingot molds for precision metallurgy,
and thin film of electronic components.
10)12)
Hence, the FeWB
composite coatings were fabricated on a steel pipe as according
to our previous study,
13)
and found that the coatings consisted of
a large number of pores which is undesired for many engineering
applications. To improve the quality of composite coating, Fe
W
2
B composite coating was selected to prepare in this study
because its reaction was improved to achieve the simple phase
of the WB compound (W
2
B).
14)
Another way to improve the
quality of composite coating is reducing the pores by incorporat-
ing some additives into reactants such as nickel (Ni), aluminum
(Al), silica (SiO
2
), and calcium peroxide (CaO
2
).
15)18)
On a point
of view, because each additive offers its own advantage for pore
minimization, the cooperation of two additives might result in a
much better performance for this. The coupled additive of iron
oxidealuminum (Fe
2
O
3
Al) was therefore used in order to mini-
mize the number of pores presenting in the composite coatings.
Its high adiabatic temperature (T
ad
) would enhance the heat of
reaction that helps its products in liquid state would easily drive
the heavy phase to the center. Then the gaseous phase would
expedient to be eliminated. Moreover, its products would provide
the FeOAl
2
O
3
spinel phase exhibiting a very high hardness as
the earlier work of Xiao et al.
19)
2. Experimental
2.1 Raw materials
The major reactants were wolframite mineral [Fe(Mn)WO
4
,
94.76% purity, particle size < 70 ¯m, Sakorn minerals Co., Ltd.,
Thailand], aluminum (Al, 93% purity, particle size < 50 ¯m,
Hi-Media), and boron oxide (B
2
O
3
, 99% purity, particle size <
80 ¯m, Sigma-Aldrich) powders. The additive reactants of iron
oxide powder (Fe
2
O
3
, 97% purity, particle size < 80 ¯m, Sigma-
Aldrich) was mixed with Al powder according to the stoichiom-
etric requirement of reaction (1).
Fe
2
O
3
ðsÞþ 2AlðsÞ! 2FeðsÞþ Al
2
O
3
ðsÞ ð1Þ
³
Corresponding author: S. Niyomwas; E-mail: sutham.n@psu.ac.th
Journal of the Ceramic Society of Japan 124 [10] 1123-1126 2016 Full paper
©2016 The Ceramic Society of Japan
DOI http://dx.doi.org/10.2109/jcersj2.16122
1123