Modern materials and technologies in the production of artificial casting

The publication highlights the production of artistic castings by investment casting using combined ceramic molds. The features of the application of a refractory coating, duplex curing of ceramic shells, cutting of molds, removal of the model composition, annealing of ceramic molds, pouring and separation of the gating‑feeding system under conditions of mass production are considered. Hydrolyzed ethyl silicate (ETS) and aqueous alkaline silica sol are used as a binder. The hydrolysis is carried out with an acidic catalyst. The strength of forms on an aqueous binder before calcination (bending strength σi) is from 1.5 to 2 MPa. The presented technology allows flexible coverage of the entire range of art products. Castings weighing from 5 to 10 kg can be produced in one batch, which significantly reduces the production cycle.

Study and Use of Rice Husk Ash as a Source of Aluminosilicate in Refractory Coating

The utilisation of rice husk ash (RHA) as an aluminosilicate source in fire-resistant coating could reduce environmental pollution and can turn agricultural waste into industrial wealth. The overall objective of this research is to develop a rice-husk-ash-based geopolymer binder (GB) fire-retardant additive (FR) for alkyd paint. Response surface methodology (RSM) was used to design the experiments work, on the ratio of RHA-based GB to alkyd paint. The microstructure behaviour and material characterisation of the coating samples were studied through SEM analysis. The optimal RHA-based GB FR additive was formulated at 50% wt. FR and 82.628% wt. paint. This formulation showed the result of 270 s to reach 200 °C and 276 °C temperature at equilibrium for thermal properties. Furthermore, it was observed that the increased contents of RHA showed an increment in terms of the total and open porosities and rough surfaces, in which the number of pores on the coating surface plays an important role in the formation of the intumescent char layer. By developing the optimum RHA-based GB to paint formulation, the coating may potentially improve building fire safety through passive fire protection.

Spontaneous formation of multilayer refractory carbide coatings in a molten salt media

Refractory materials hold great promise to develop functional multilayer coating for extreme environments and temperature applications but require high temperature and complex synthesis to overcome their strong atomic bonding and form a multilayer structure. Here, a spontaneous reaction producing sophisticated multilayer refractory carbide coatings on carbon fiber (CF) is reported. This approach utilizes a relatively low-temperature (950 °C) molten-salt process for forming refractory carbides. The reaction of titanium (Ti), chromium (Cr), and CF yields a complex, high-quality multilayer carbide coating composed of 1) Cr carbide (Cr3C2), 2) Ti carbide, and 3) Cr3C2 layers. The layered sequence arises from a difference in metal dissolutions, reactions, and diffusion rates in the salt media. The multilayer-coated CFs act as a permeable oxidation barrier with no crystalline degradation of the CFs after extreme temperature (1,200 °C) and environment (oxyacetylene flame) exposure. The synthesis of high-quality multilayer refractory coating in a fast, efficient, easy, and clean manner may answer the need for industrial applications that develop cheap and reliable extreme environment protection barriers.

Coating based on basalt protection metal structures

The paper present the results of the synthesis of a new refractory coating based on basalt for the protection of metal construction under conditions of cavitation. Initial basalt samples obtained from the locality Vrelo - Kopaonik. The basalt based refractory filler was obtained by crushing and grinding selected samples of basalt rock. XRD, SEM and optical microscopy methods were used to characterize the obtained filler samples. The research defined the composition of basalt -based coating with epoxy resinbased binder, organic additives and organic solvent. The resistance properties of protective coatings applied to metal surface were investigated using the ultrasonic vibration method with a stationary sample according to the ASTM G 32 standard. To evaluate the resistance of the sample surface to the action of cavitation, the sample surface was examined before and during testing. The surface of the samples was monitored by scanning electron microscopy in order to analyze the morphology of surface damage. Computer image analysis according to the Image Pro Plus program was applied to assess the damage to the sample surface. The obtained test results showed high resistance of the coating layers to the effect of cavitation, with small mass losses, small damage to the coating surface and a cavitation rate of 0,1 mg/min.

The Effect of Silica Fused Addition as Filler on Zircon Based Refractory Coating

Refractory coating is widely used in metal casting process to protect the mold from direct contact with molten metal. This coating also could improve the surface quality of casting product. Zircon is common materials that used as filler, but the materials cost is quite high. Therefore, alternative material is needed to make partial substitution of the filler. Silica Fused can be considered as filler because it has good refractoriness. This study aims to determine silica fused is reliable as an alternative to substitute zircon filler. The samples were made with 16%, 18%, and 20% silica fused addition and different treatment which were heated and non-heated drying. Particle size and distributions of the filler were analyzed using Particle Size Analysis. Viscosity measurement has been done to coating slurry to analyze the rheological characteristics of the slurry. The surface morphology of dried coating was taken using Scanning Electron Microscope. XRD test also has been done to analyse the compound. The quality of coating was determined from the thermal stability of the coating that was analyzed using Simultaneous Thermal Analysis. The result shows that silica fused is reliable as an alternative material for filler partial substitution.

On the influence of hypersonic flow at the speed of a reflow heat-proof surface in terms of destruction

The results on the distribution of heat flows coming to the refractory plate of a hypersonic aircraft moving at different distances from the Earth's surface with cosmic velocities are obtained. The results of studies related to the study of phase transitions in the wall boundary layer occurring during the flow of hypersonic flow ablating surface are presented. The influence of the catalytic wall on the heat flow is considered. The main attention is paid to the analysis of the surface entrainment of high-speed aircraft, based on a detailed account of the mechanism of heterogeneous catalytic reactions in the conditions of surface mass transfer. The temperature distribution over the thickness of the boundary layer at the critical point of a blunted body with a refractory coating for a particular section of the flight path is given. Mass entrainment from the surface of crystalline refractory bodies is determined. Ill. 7. Ref. 16.

Influence of Solid Lubricants on the Working Efficiency of a Coated-Carbide Cutting Tool under Interrupted Cutting Conditions

In order to increase the working efficiency of coated-carbide cutting tool under interrupted cutting conditions it is most efficient to use abrasion resistant refractory coating and solid lubricants.

Silica-Kaolin Mix Effect on Evaporative Pattern Castings Surface Roughness

The influence of the refractory coating which is a mixture of silica flour and kaolin on the surface roughness of the plate castings produced using evaporative patterns had been considered in this work. The kaolin was used as a binder and ratio method was employed to form basis for the factorial design of experiment which led to nine runs of experiments. Methyl alcohol at 99% concentration was used as the carrier for the transfer of the coating to the surface of the patterns. Pouring temperature was observed as a process parameter alongside the mix ratios of the coating. Attempts were made to characterize the refractory coating by using two methods; differential thermal analysis (DTA) and X-ray diffraction. Attempt was also made to characterize the casting material. Gating system design was done for the plate casting to determine the correct proportions of the gating parameters in order to construct the gating system properly to avoid turbulence during pouring of liquid metal. A digital profilometer was used to take the measurements of the surface roughness. It was observed that the mix ratio 90% silica flour-10% kaolin produced the lowest value of the surface roughness of the plate castings and had the lowest material loss in the DTA test. The pouring temperature of 650°C produced best casting.