Toughening of Ceramic Shell Mould with Rice Husk Fiber (CSm-RH) to Improve Strength Property and Mould Performance

For ages, ceramic shell mould (CSm) have been extensively applied in investment casting industry. The formation of CSm requires multiple steps of dipping, layering drying and firing stages. The later steps are very crucial as the solidification thin layer CSm that consist of loose ceramic particles easily cracks when exposed to the higher thermal effect. The inclusion of fiber or any reinforces phases is able to enhance fired ceramic body and also strengthen the green ceramic structure. Thus, the feasibility of rougher NaOH treated rice husk fiber (RHT) prior embedded into composited structure has shown a significant CSm improvement by induced a better adhesion properties and larger bonding area with brittle ceramic matrix, resulted in increased green strength (1.34 MPa) and fired body strength (4.32 MPa). Owing to the decomposed of lignin layer in CSm with untreated rice husk fiber (CSm-RHU) exhibited a higher porosity that provide a better permeation paths of air flow during molten metal pouring as increased 30 % from the standard CSm permeability, giving an enormous benefit for investment casting cooling process. Overall, the incorporation of RHT fiber in a CSm matrix of both green and fired body governed in toughening of brittle ceramic body, hence avoid failure to the casting mould.

Dependence of the fractality of the silica gel on the method of sol emulsification

The article presents experimental data confirming the effect of capillary active substance (surfactants) and sedimentation stability on the final structure of the gel with stabilized silicic acid. Studies of the macrostructure of silica gel depending on the method of emulsifi ation of silicic acid sol and the effect of the resulting fractality on the strength of the mold are presented.The direction of modifying the binder for lost‑wax casting (LWC) with obtaining the specified properties of the ceramic shell is shown.The complex effect of organic polymers on the sol – gel system has been established. The conclusion is made about the possibility of using an aqueous dispersion of acrylic to form a given structure of a silica gel.

Interface Reaction between Directional Solidified Superalloy DZ40M and Ceramic Mould

The interfaces between DZ40M directional solidified superalloy and ceramic mould (SiO2-base core and Al2O3-base shell) was studied by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results showed that there was a serious interface reaction between DZ40M and ceramic cores，which resulted in many reaction pits (~100μm deep), Si rich residue alloys and Zr rich subglobose oxides on the inner surface. And the interface reaction between DZ40M and ceramic shell induced a ~50μm of pink sand burning layer. The thermal analysis showed that the reactions between DZ40M and core or shell were similar: the active alloy constituents (Zr, Al, Ti and Cr) were oxidized and became oxides or solid solution with the core or shell components (SiO2, Al2O3 or Fe2O3), but the interface characterization of DZ40M/core and DZ40M/shell was different because the shell had the main content of Al2O3 and impurity of Fe2O3, while those of the core were SiO2 and CaO, respectively.

3D Printing of Ceramic Shell Molds for Precision Casting of Turbine Blades

Traditionally, the technology used in the production of gas turbine blade castings characterized by a large number of technological conversions, high labor costs with a large amount of manual labor and the need to produce various types of complex and expensive equipment at different stages of production. This work aims to reduce the time and money spent on the manufacturing of ceramic shell shapes — a form suitable for the standard methods of precision casting by traditional heat-resistant nickel alloys. The proposed approached involves obtaining a shell shape with an internal core as a single, non-assembled product, without lengthy and time-consuming design and manufacturing processes involved in forming equipment for the production of castings based on smelted models. The proposed method is based on the use of 3D printing with refractory ceramic pastes. Using both uncooled and cooled blades as examples, models of casting molds were designed, technological processes were developed, and ceramic shell molds were manufactured. Experimental casting into a manufactured ceramic shell mold for an uncooled blade with a bandage shelf was performed and showed satisfactory results.

Effect of Pouring Temperature and Heating of Ceramic Shells Mould on Projection of Thin Wall Castings

One of the research directions of this study is to determine the possibility of making precise, thin-walled castings from selected iron alloys. The scope of research work is aimed at determining the applicability of the casting process of selected iron alloys with the technology of wax pattern, for making precise castings with a wall thickness of less than 3 mm. The article presents the results of tests carried out for experimental castings with the shape of steps, characterized by different wall thicknesses: 1 mm, 5 mm, 10 mm, 25 mm. The castings were made of LH14, Gs42crMo4, L35H7MP2, LH26N9, 316L cast steel, and a new alloy marked “0”. The metal was smelted in an induction furnace with a capacity of 150 kg. The technology of ceramic shell mould used in the plant was used to make the experimental castings. Ceramic shell moulds were heated in a chamber furnace at a fixed temperature. The time of annealing the ceramic mould was constant in a ceramic form. The following parameters were variable during the tests: iron alloy, pouring temperature, and annealing temperature of the ceramic shell mould.