The article presents methodology for testing the electric strength of vacuum chambers designed for modern medium voltage switchgear developed by the authors, using two innovative test stands designed and constructed by the research team above. Verification of the correctness of operation of the test stands, as well as the validity of the developed methodology was carried out by performing a series of tests. It was determined that below certain pressure values in the tested chamber (from about 5.0×10 ⁰ Pa for station 1 and for about 4.0×10 ^-1 Pa for station 2), the electric strength maintains a constant value, which guarantees stable operation of the vacuum chamber. The values of the total measurement uncertainty for the electric strength tests were also estimated.

This paper presents the recent advances in pervaporative reduction of sulfur content in gasoline. Methods of preliminary selection of membrane active layer material are presented. Interactions between gasoline components (typical hydrocarbon and sulfur species) and membranes are showed. Influence of pervaporation process parameters i.e. feed temperature, downstream pressure and feed flow rate on the separation efficiency is discussed. Investigations of the influence of sulfur concentration in fluid catalytic cracking (FCC) gasoline on membrane performance have been conducted. A series of PV tests was carried out to investigate the separation properties of the commercial composite membrane with an active layer made of poly(dimethylsiloxane) and to determine the efficiency of organic sulphur compound (thiophene) removal from model thiophene/n-heptane mixture depending on its concentration.

This study manufactured a SiC coating layer using the vacuum kinetic spray process and investigated its microstructure and wear properties. SiC powder feedstock with a angular shape and average particle size of 37.4 μm was used to manufacture an SiC coating layer at room temperature in two different process conditions (with different degrees of vacuum). The thickness of the manufactured coating layers were approximately 82.4 μm and 129.4 μm, forming a very thick coating layers. The SiC coating layers consisted of α-SiC and β-SiC phases, which are identical to the feedstock. Cross-sectional observation confirmed that the SiC coating layer formed a dense structure. In order to investigate the wear properties, ball crater tests were performed. The wear test results confirmed that the SiC coating layer with the best wear resistance achieved approximately 4.16 times greater wear resistance compared to the Zr alloy. This study observed the wear surface of the vacuum kinetic sprayed SiC coating layer and identified its wear mechanism. In addition, the potential applications of the SiC coating layer manufactured using the new process were also discussed.

This paper discusses issues related to optimising the technological parameters of the process of brazing gold in a vacuum

furnace. An investigation of the brazing process was carried out for materials used in constructing components for aircraft engine

fuel systems. The vacuum brazed material was AMS 5510 stainless steel (in the form of plates and pipes). AMS 4787 (BAu-4) was

used as the brazing filler. In particular, the influence of the method of preparing the surface on solder spreading and the thickness

of the diffusion zone were analysed. The best spreading of solder was obtained for nickel plated surfaces. When the sample surface

was more rough or scratched, the effect of the spreading of solder was limited and the diffusion process of the solder into the base

material became dominant. Moreover, the influence of the brazing temperature on microstructure changes and on interdiffusion

of the AMS 5510 stainless steel/BAu-4 solder system was determined. It was observed that an increase in the brazing temperature

modifies the morphology of the formed joint by forming a massive and rounded phase. Furthermore, an increase in the brazing

temperature enhances the exchange of components.

Brazing of two dissimilar structural materials; Zircaloy-4 and SS-316L was performed at 900oC under high vacuum conditions. The metallic glass ribbons (Zr55Cu30Al10Ni2Fe3-at. %) of 30 µm thickness, were used as an interlayer. The bonded region was characterized by scanning electron microscope (SEM), energy dispersive spectroscope (EDS) and microhardness testing. The metallurgical bond formation was due to compositional changes in the molten interlayer and later on its subsequent solidification. Assessment of the bonded zone (BZ) revealed three distinct regions (Region-I, Region-II and Region-III). Diffusion transformation was observed in Region-I and Region-III which were interface with base alloys SS-316L and Zircaloy-4 respectively. However, Region-II at the middle of the BZ was composed of isothermally and athermally solidified portions. The highest values of Microhardness were observed in Region-III which was due to the presence of hard phases. Moreover, a crack parallel to BZ was observed in Region-III and was attributed to differential contraction of base alloys during cooling. Maximum shear stress acting on the BZ was calculated and correlated to the brittle phase cracking.

The work deals with the influence of change in the filling conditions of the ceramic moulds with plaster binder on the presence of gaseous

porosity and the microstructure of the achieved test castings with graded wall thickness. Castings made of EN AC-44000 alloy, produced

either by gravity casting, or by gravity casting with negative pressure generated around the mould (according to the Vacumetal

technology), or by counter-gravity casting were compared. The results of examinations concerning the density of the produced castings

indicate that no significant change in porosity was found. The increased size of silicon crystals was found for the increased wall

thicknesses due to the slower cooling and solidification of castings.

Deoxidation of steel with carbon under reduced pressure is often used for increasing the steel purity. Suitable units for this purpose in

foundries are vacuum induction furnaces. Possibilities of increasing the steel purity by deoxidation with carbon in the vacuum induction

furnace were studied for the steel for the petrochemistry of specific composition 25Cr/35Ni. The charge composed of the return material

only was melted in the air. During melting the charge oxidized and the oxidizing slag formed. Chemical composition of steel, morphology,

chemical composition of inclusions in the steel and chemical composition of slag after vacuuming were studied on the basis of samples

taken before and after vacuuming. Temperature and oxygen activity were measured before and after vacuuming. Globular inclusions with

dominant content of silicon and manganese were observed in steel before and after vacuuming. Contents of total oxygen in steel didn’t

change significantly during vacuuming. On the basis of composition of inclusions and measured oxygen activity the activity of Cr2O3

in

inclusions was calculated. A slag sample was taken after vacuuming and equilibrium oxygen activity in steel with regard to the Cr2O3

content in the slag was estimated from the slag composition. Equilibrium oxygen activity in relation to the Cr2O3 content in the slag was

higher than equilibrium activity measured in the steel. For this reason it is not possible, under the studied conditions, to decrease oxygen

content in steel during vacuuming.

The paper presents the results of investigations concerning the influence of negative (relative) pressure in the die cavity of high pressure

die casting machine on the porosity of castings made of AlSi9Cu3 alloy. Examinations were carried out for the VertaCast cold chamber

vertical pressure die casting machine equipped with a vacuum system. Experiments were performed for three values of the applied gauge

pressure: -0.3 bar, -0.5 bar, and -0.7 bar, at constant values of other technological parameters, selected during the formerly carried initial

experiments. Porosity of castings was assessed on the basis of microstructure observation and the density measurements performed by the

method of hydrostatic weighing. The performed investigation allowed to find out that – for the examined pressure range – the porosity of

castings decreases linearly with an increase in the absolute value of negative pressure applied to the die cavity. The negative pressure value

of -0.7 bar allows to produce castings exhibiting porosity value less than 1%. Large blowholes arisen probably by occlusion of gaseous

phase during the injection of metal into the die cavity, were found in castings produced at the negative pressure value of -0.3 bar. These

blowholes are placed mostly in regions of local thermal centres and often accompanied by the discontinuities in the form of interdendritic

shrinkage micro-porosity. It was concluded that the high quality AlSi9Cu3 alloy castings able to work in elevated temperatures can be

achieved for the absolute value of the negative pressure applied to the die cavity greater than 0.5 bar at the applied set of other parameters

of pressure die casting machine work.

The performed examinations concerning the process of filling the plaster ceramic moulds with aluminium alloys allowed to assess the

influence of various methods of introducing the metal into the mould cavity on the macro- and microstructure of the obtained experimental

castings. The comparison was performed for castings with graded wall thickness made either of EN AC-44000 alloy or of EN AC-46000

alloy, produced either by gravity casting, or by gravity casting with negative pressure generated around the mould (according to the

Vacumetal technology), or by counter-gravity casting. It was found that the silicon crystals grow in size with an increase in wall thickness

due to the slower cooling and solidification of castings.

Vacuum conditions in foundry installations are generated using electric-driven vacuum pumps. The purpose of the experiment is to evaluate the performance of a vacuum-assisted system for compaction of moulding sand basing on registered plots of selected electric power parameters of the power-supplying system of the pumps. Model testing done on an experimental vacuum system installation, power-supplied from a system incorporating the recorders of instantaneous current and voltage values. Following the numerical procedure, the experimental data are analysed to yield mathematical relationships between the variations of the generated vacuum pressure levels and variations of selected electric power parameters. Registered and computed values of selected parameters: instantaneous and RMS voltage and current values, active, reactive and apparent power levels and power coefficient allow for diagnosing the adequacy and reliability of the system operation. According to the authors, the applied monitoring of the power parameters of a vacuum-assisted installation may become an effective and easy practical method of evaluating the performance of such installations, used also in foundry plants.

In this article the main problems related with the proper choice of the design and operation parameters of vacuum installation in vacuum moulding system have been discussed. In such system a vacuum are generated using electric-driven vacuum pumps. The aim of the experiment is to evaluate the performance of a vacuum system basing on registered plots of selected electric power parameters of the power-supplying system of the pumps with parallel measurements instantaneous values of pressure in selected points of model stand. The measurements system for power-supply unit has incorporated the recorders of instantaneous current and voltage values. Following the suitable numerical procedure, the experimental data are analysed to yield mathematical relationships between the variations of the generated vacuum pressure levels and variations of selected electric power parameters. According to the authors, the applied measurements system of the parameters of a vacuum-assisted installation may become an effective and easy practical method of evaluating the performance of such installations, used also in industry.

The paper presents the use of rapid prototyping technology of three dimensional printing (3DP) to make a prototype shell casting mold. In

the first step, for identification purposes, a mold was prepared to enable different alloys to be cast. All molds being cast were designed in a

universal CAD environment and printed with the zp151 composite material (Calcium sulfate hemihydrate) with a zb63 binder (2-

pyrrolidone). It is designated to be used to prepare colourful models presenting prototypes or casting models and molds. The usefulness of

3DP technology for use with copper alloys, aluminum and zinc was analyzed. The strength of the mold during casting was assumed as a

characteristic comparative feature in the material resistance to high temperature, the quality of the resulting casting and its surface

roughness. Casting tests were carried out in vacuum – pressure casting. The casting programs applied, significantly increased the quality of

castings and enabled precise mold submergence. Significant improvement was noted in the quality compared to the same castings obtained

by gravity casting.