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Investment casting has been used to manufacture weapons, jewellery
and
investment casting during the ancient civilization. Today, its
applications include jewellery/art castings, turbine blades and many
more industrial/scientific components. The present paper reviews
various investigations made by researchers in different stages of
investment casting and highlights their importance. The paper initially
highlights the investigations made on pattern wax properties, effects
of blending, additives and fillers. Different ways through which
pattern properties (like surface finish, dimensional accuracy, etc.)
could be enhanced by properly controlling the injection processing
parameters are thoroughly discussed. The paper also looks into the
investigations made to enhance the strength, surface finish, etc. of
ceramic shell for ferrous alloys/non-ferrous alloys as well as
superalloys in investment casting. Investigations made on incorporation
of nylon fibers and polymer additions confirm that a ceramic shell
reinforced with nylon fibers attains additional permeability compared
to the one with polymer additions.
Different investigations carried out on autoclave dewaxing and
microwave dewaxing conclude that the wax properties are less altered
with microwave dewaxing when compared to an autoclave dewaxing. Some
recent investigations carried out on pouring and post-treatment
operations are also discussed in the paper. The advent and emergence of
rapid prototyping in shell mold casting are broadly
exposed in the subsequent sections of the paper. Various aspects of
rapid prototyping like rapid investment casting, rapid freeze
prototyping, etc., along with their advantages are projected. The
emerging areas of applications of rapid prototyping like dentistry,
etc., are duly discussed.
The casting of titanium based alloys presents considerable problems,
including the extensive interactions that occur between the metal and
refractory. In this work, CaO stabilised zirconia was used as a primary
coat material on the investment casting mould. The reaction between the
zirconia face-coat and a Ti-46Al-8Nb-1B alloy was evaluated at three
mould pre-heating temperatures: 500°C, 1000°C and 1200 °C. The
effect of casting dimensions on interaction was also included in this
work and the computer simulation of metal cooling profiles was carried
out to assist the analysis. Higher mould pre-heat temperature and
larger casting dimensions enhanced the interaction between the shell
and the TiAl alloy associated with longer metal solidification time.
During the high temperature casting process, not only were O and Zr
observed penetrating into the metal from the decomposition of the
face-coat materials, but also Si which had penetrated from the backup
coat was found to have interacted with the metal.
Investment casting is competitive with all other casting processes
where the size of the product is within a mutually castable range.
Though investment casting is used to produce metal parts of any
intricate shapes with excellent surface finish, it suffers from long
lead time and high tooling costs, which makes it uneconomical for the
production of either single casting, or small and medium production
units. These problems could be overcome by the applications of rapid
prototyping and rapid tooling technologies for low-volume investment
casting production runs. The present article analyzes different
classifications of rapid prototyping techniques and it reviews various
investigations made on the usability of rapid prototyping- and rapid
tooling-integrated investment casting process, with their advantages
and limitations. The emerging areas of applications of rapid
prototyping like dentistry, jewelry, surgical implants, turbine blades,
etc., are accordingly discussed. Further, an elaborate discussion is
made on the application of newer technologies for directly developing
ceramic shells. This article also emphasizes on various future scopes
possible in rapid prototyping-integrated investment casting process.
Investment casting process is known to its capability of
producing clear net shape, high-dimensional accuracy and intricate
design. Consistent research effort has been made by various researchers
with an objective to explore the world of investment casting.
Literature review revealed the effect of processing parameters on
output parameters of cast specimen. This article highlights the
advancements made and proposed at each step of investment casting and
its hybridization with other process. Besides, investment casting has
always been known to manufacture parts such as weapons, jewellery item,
idols and statues of god and goddess since 3000 BC; this article
reviews the present applications and trends in combination of rapid
prototyping technique as integrated investment casting to serve in
medical science. Advancements in shell moulding with incorporation of
fibre and polymer, development of alternative feedstock filament to
fused deposition modelling are duly discussed. The aim of this review
article is to present state of art review of investment casting since
3200 BC. This article is organized as follows: in section
‘Introduction’, introduction to investment casting steps is given
along with researches undertaken at each step; in section ‘Rapid
prototyping technique’, background is given on the concept of rapid
prototyping technique by examining the various approaches taken in the
literature for defining rapid prototyping technique; section
‘Biomedical applications of RPT’ presents the medicine or biomedical
applications of investment casting and rapid prototyping technique;
section ‘Future trends’ provides some perspectives on future research
and section ‘Conclusion’ closes the article by offering conclusions.
In order to improve the properties of silicon sol shell for
shell
mold casting process, natural plant fibers combined with aluminum
silicate fibers at natural-to-aluminum silicate fibers mass ratio of
1:1 were mixed into the slurries preparing for fiber-reinforced shell.
The flexural strength of specimens of green shells, fired shells at
different temperatures and the self-loaded deformation of the latter at
elevated temperature were investigated. The fracture surface of shell
specimens was observed by SEM. The results show that the green strength
of shell specimens increases firstly and then decreases with variation
of content of fiber from 0.2% to 1.0%. However, the self-loaded
deformation at elevated temperature firstly decreases and then
increases. The green strength of shell specimens reinforced with 0.6%
fibers reaches the maximum of 2.94 MPa. The bending strength of shell
specimens reinforced with 0.6% fibers fired at 900℃ reaches 4.04 MPa,
approaching that of the non-reinforced shell specimens. It is found by
SEM that the failure of the fiber-reinforced shell specimens at the
applied load is resulted in breakdown of silicon sol films and
pulling-out, fracturing and debonding of fibers in the shell.
The development of manufacturing processes for high-performance
investment casting components in turbomachinery is an iterative
process, which takes a lot of development time for engineers and
foundry occupation. The reduction of these expensive preliminary tests
is possible by combining probabilistic methods with modern simulation
tools for the numerical description of the
what is investment casting and
solidification processes. Starting from the deterministic simulation of
the casting process, the casting and solidification parameters
including their production tolerances are taken into account in the
probabilistic simulation. Through a multi-dimensional statistical
analysis of the numerous parameters of the casting process and the
achieved virtual casting results, the correlations between the process
parameters and component quality can be worked out. Furthermore, a
design of experiment (DoE) was performed with real castings to confirm
the influence of the main parameters on the result quantities.
Mechanical and microstructural characterizations of appropriate cast
specimens allow a validation of the simulation results and the
formulation of casting parameter–microstructure–property relations.
The mechanical properties are studied by uniaxial hot tensile tests
using standard and small-scale specimens. Furthermore, the uniaxial
fatigue behavior and the life times at elevated temperatures are
investigated.
In order to reduce the interaction between the Ti alloys and
ceramic shell during the casting, materials with high thermal and
chemical inertness were used in investment casting. An investigation
was undertaken to analyze the influence of the change of binder systems
on the slurries, facecoats and the thermo-chemical properties of the
facecoat systems using an Y2O3–ZrO2 filler material. The results
showed that, using alumina-sol as the binder in the slurry gave the
longest life of around three days followed by that using the
commercially available zirconia-sol at around 6 h, and the yttria sol
based slurry giving a shortest life of around 1.5 h. Meanwhile using
the alumina-sol can also enhance the facecoat sintering properties.
There was no obvious evidence observed that the change of the binder
system influenced the facecoat chemical inertness.
and
investment casting during the ancient civilization. Today, its
applications include jewellery/art castings, turbine blades and many
more industrial/scientific components. The present paper reviews
various investigations made by researchers in different stages of
investment casting and highlights their importance. The paper initially
highlights the investigations made on pattern wax properties, effects
of blending, additives and fillers. Different ways through which
pattern properties (like surface finish, dimensional accuracy, etc.)
could be enhanced by properly controlling the injection processing
parameters are thoroughly discussed. The paper also looks into the
investigations made to enhance the strength, surface finish, etc. of
ceramic shell for ferrous alloys/non-ferrous alloys as well as
superalloys in investment casting. Investigations made on incorporation
of nylon fibers and polymer additions confirm that a ceramic shell
reinforced with nylon fibers attains additional permeability compared
to the one with polymer additions.
Different investigations carried out on autoclave dewaxing and
microwave dewaxing conclude that the wax properties are less altered
with microwave dewaxing when compared to an autoclave dewaxing. Some
recent investigations carried out on pouring and post-treatment
operations are also discussed in the paper. The advent and emergence of
rapid prototyping in shell mold casting are broadly
exposed in the subsequent sections of the paper. Various aspects of
rapid prototyping like rapid investment casting, rapid freeze
prototyping, etc., along with their advantages are projected. The
emerging areas of applications of rapid prototyping like dentistry,
etc., are duly discussed.
The casting of titanium based alloys presents considerable problems,
including the extensive interactions that occur between the metal and
refractory. In this work, CaO stabilised zirconia was used as a primary
coat material on the investment casting mould. The reaction between the
zirconia face-coat and a Ti-46Al-8Nb-1B alloy was evaluated at three
mould pre-heating temperatures: 500°C, 1000°C and 1200 °C. The
effect of casting dimensions on interaction was also included in this
work and the computer simulation of metal cooling profiles was carried
out to assist the analysis. Higher mould pre-heat temperature and
larger casting dimensions enhanced the interaction between the shell
and the TiAl alloy associated with longer metal solidification time.
During the high temperature casting process, not only were O and Zr
observed penetrating into the metal from the decomposition of the
face-coat materials, but also Si which had penetrated from the backup
coat was found to have interacted with the metal.
Investment casting is competitive with all other casting processes
where the size of the product is within a mutually castable range.
Though investment casting is used to produce metal parts of any
intricate shapes with excellent surface finish, it suffers from long
lead time and high tooling costs, which makes it uneconomical for the
production of either single casting, or small and medium production
units. These problems could be overcome by the applications of rapid
prototyping and rapid tooling technologies for low-volume investment
casting production runs. The present article analyzes different
classifications of rapid prototyping techniques and it reviews various
investigations made on the usability of rapid prototyping- and rapid
tooling-integrated investment casting process, with their advantages
and limitations. The emerging areas of applications of rapid
prototyping like dentistry, jewelry, surgical implants, turbine blades,
etc., are accordingly discussed. Further, an elaborate discussion is
made on the application of newer technologies for directly developing
ceramic shells. This article also emphasizes on various future scopes
possible in rapid prototyping-integrated investment casting process.
Investment casting process is known to its capability of
producing clear net shape, high-dimensional accuracy and intricate
design. Consistent research effort has been made by various researchers
with an objective to explore the world of investment casting.
Literature review revealed the effect of processing parameters on
output parameters of cast specimen. This article highlights the
advancements made and proposed at each step of investment casting and
its hybridization with other process. Besides, investment casting has
always been known to manufacture parts such as weapons, jewellery item,
idols and statues of god and goddess since 3000 BC; this article
reviews the present applications and trends in combination of rapid
prototyping technique as integrated investment casting to serve in
medical science. Advancements in shell moulding with incorporation of
fibre and polymer, development of alternative feedstock filament to
fused deposition modelling are duly discussed. The aim of this review
article is to present state of art review of investment casting since
3200 BC. This article is organized as follows: in section
‘Introduction’, introduction to investment casting steps is given
along with researches undertaken at each step; in section ‘Rapid
prototyping technique’, background is given on the concept of rapid
prototyping technique by examining the various approaches taken in the
literature for defining rapid prototyping technique; section
‘Biomedical applications of RPT’ presents the medicine or biomedical
applications of investment casting and rapid prototyping technique;
section ‘Future trends’ provides some perspectives on future research
and section ‘Conclusion’ closes the article by offering conclusions.
In order to improve the properties of silicon sol shell for
shell
mold casting process, natural plant fibers combined with aluminum
silicate fibers at natural-to-aluminum silicate fibers mass ratio of
1:1 were mixed into the slurries preparing for fiber-reinforced shell.
The flexural strength of specimens of green shells, fired shells at
different temperatures and the self-loaded deformation of the latter at
elevated temperature were investigated. The fracture surface of shell
specimens was observed by SEM. The results show that the green strength
of shell specimens increases firstly and then decreases with variation
of content of fiber from 0.2% to 1.0%. However, the self-loaded
deformation at elevated temperature firstly decreases and then
increases. The green strength of shell specimens reinforced with 0.6%
fibers reaches the maximum of 2.94 MPa. The bending strength of shell
specimens reinforced with 0.6% fibers fired at 900℃ reaches 4.04 MPa,
approaching that of the non-reinforced shell specimens. It is found by
SEM that the failure of the fiber-reinforced shell specimens at the
applied load is resulted in breakdown of silicon sol films and
pulling-out, fracturing and debonding of fibers in the shell.
The development of manufacturing processes for high-performance
investment casting components in turbomachinery is an iterative
process, which takes a lot of development time for engineers and
foundry occupation. The reduction of these expensive preliminary tests
is possible by combining probabilistic methods with modern simulation
tools for the numerical description of the
what is investment casting and
solidification processes. Starting from the deterministic simulation of
the casting process, the casting and solidification parameters
including their production tolerances are taken into account in the
probabilistic simulation. Through a multi-dimensional statistical
analysis of the numerous parameters of the casting process and the
achieved virtual casting results, the correlations between the process
parameters and component quality can be worked out. Furthermore, a
design of experiment (DoE) was performed with real castings to confirm
the influence of the main parameters on the result quantities.
Mechanical and microstructural characterizations of appropriate cast
specimens allow a validation of the simulation results and the
formulation of casting parameter–microstructure–property relations.
The mechanical properties are studied by uniaxial hot tensile tests
using standard and small-scale specimens. Furthermore, the uniaxial
fatigue behavior and the life times at elevated temperatures are
investigated.
In order to reduce the interaction between the Ti alloys and
ceramic shell during the casting, materials with high thermal and
chemical inertness were used in investment casting. An investigation
was undertaken to analyze the influence of the change of binder systems
on the slurries, facecoats and the thermo-chemical properties of the
facecoat systems using an Y2O3–ZrO2 filler material. The results
showed that, using alumina-sol as the binder in the slurry gave the
longest life of around three days followed by that using the
commercially available zirconia-sol at around 6 h, and the yttria sol
based slurry giving a shortest life of around 1.5 h. Meanwhile using
the alumina-sol can also enhance the facecoat sintering properties.
There was no obvious evidence observed that the change of the binder
system influenced the facecoat chemical inertness.