International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

The study identifies the main casting defects at the interface between a cast iron ring insert and an Al-Si piston and determines their principal causes. Industrial investigations of 1000 pistons showed that the Al-Fin process increases Fe content in the AlSi9 alfining alloy, promoting long plate-like β-Al5FeSi phases and porosity in the joint region. Gas contamination by oxides and hydrogen further weakens the bond. The addition of approximately 0.05 wt.% Mn and intermediate re-refining of the AlSi9 alloy were found to improve the microstructure and reduce porosity, thereby increasing the quality of the insert-piston joint.

The study determines the effect of gas-bubbling refining time on porosity and mechanical properties of low-pressure AlSi7Mg alloy castings under industrial conditions. Refining was performed with an NH2 mixture (90% N + 10% H2) for 5.0–9.0 min. Porosity, density index, HB hardness, tensile strength Rm, 0.2% proof stress Rp0.2 and elongation A were evaluated. The optimum refining time was 7 min, giving minimum porosity and mechanical properties meeting customer requirements. Longer refining increased porosity and reduced selected mechanical properties.

Studies of the tip of a road milling cutter made of tungsten-cobalt alloy have been carried out. It is established that one of the factors influencing the wear resistance of the tip is the porosity of the sintered hard alloy. Laser treatment of the surface of the cutter tip was performed. It has been found that under certain laser radiation conditions, the number of pores in the cutter decreases.

The possibility of using hollow spheres to create highly porous materials (HPM) based on fine powders is shown. In the process of obtaining HPM, fine powder acts as a matrix, hollow spheres are used as a pore-forming agent. At the same time, in the initial state, hollow spheres are formed in the form of bead-shaped polystyrene granules (PSG) with a coated shell of fine aluminum oxide powder, followed by the removal of PSG during sintering. The shell prevents the integration of spherical voids into a single system of large pores, providing high purification fineness. It is confirmed that this technology provides an increase in throughput at a given fineness of purification.

Silica gels are one of the most widely used adsorbents. The best view of the properties of silicas as catalytic supports, adsorbents and other applications give the adsorption-texture parameters and especially the specific surface area. Hydrated silicon dioxide is amorphous (SiO2.nH2O),a reactive compound with various contains. Due to the serious practical interest of the determination of the specific surface area of materials many methods are developed and have found application. The study evaluates the impact of the surface and surface modification on the possibility of an express method for determination of specific surface areas of silica gels.

The paper deals with the problem of occurrence of internal defects in materials produced by SLM technology. The influence of the position of materials on the platform during the SLM on selected properties – porosity and corrosion resistance were examined. The reuse of non-compacted powder (three times recycled powder) and its effect on porosity and corrosion resistance of materials was also tested. Porosity was measured on metallographic sections in two perpendicular directions by image analysis, corrosion properties were tested by linear polarization method.

The results of the estimation for the influence of titanium diboride content in the initial powder mixture on the basic mechanical properties at the tests on tension and compression are presented. It is shown that the porosity of sintered at 1250 0C preforms from TiH2-TiB2 powder mixture increases with increasing of titanium diboride content in the initial charge, which is due to the manifestation of the Frenkel effect at sintering. The values of tensile strength, hardness and elastic modulus, despite some porosity growth of the sintered alloy, increase with the addition of 5 % of TiB2 powder, while increasing the content of the high modulus component in the mixture to 10 % leads to decrease in the level of these characteristics. The plasticity of sintered alloys monotonically decreases with increasing of the boride component content. At compression tests, the yield point and the compressive strength increase monotonically with increase in TiB2 content, despite the increase in porosity of the latter, due to a significantly lower effect of porosity on the value of the resistance to deformation in compression compared with tension. The use of hot forging of sintered powder preforms leads to increase of strength properties and hardness of the composites.

The potential of using the ultrafine dispersion powder material obtained by the ECA pressing from a copper powder have considered for the production of fast-acting fuse links. The dependences of the density and microhardness along the length of the sample under different deformation conditions obtained. A deformation zone of constant density is determined and recommended for using in the production of fuse links. The dependence of the electrical resistance along the sample cross-section and across the deformation axis has determined. The fuse links calculation procedure has proposed.

Theoretical and experimental data on the impact of heating rate during spark-plasma sintering on densification kinetics, grain size and capillary pressure in powder compacts, based on Fe, are given. It is found out, that an increase of heating rate in range from 10 °C/s to 20 °C/s leads to acceleration of process of obtainment of non-porous compacts and decrease of structure grain size.