Investment casting has been used to manufacture weapons, jewellery


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


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


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.

  • Created: 04-01-22
  • Last Login: 04-01-22

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