Experimental Tests of Discrete Strengthened Elements of Machine-Building Structures

Computer simulation and bench tests of components and full-scale structures of internal combustion engine are performed in order to evaluate discrete and continual strengthening technology. The contact pressure distributions, friction coefficients, wear, roughness and hardness of the contacting surfaces of the tested machine parts were determined. The numerical characteristics that determine the effectiveness of such combined strengthening method are established. Conceptual fundamentals of discrete continual strengthening have been developed. Positive effects in the “load – contact – friction – wear” chain were found due to the proposed strengthening method. The positive effect of the coordination of micro and macroscale processes and states of loaded parts, which are strengthened by the discrete and continuous method, is also established. It is confirmed that the entire set of tribo-mechanical characteristics is improved with such strengthening, in contrast to traditional methods, an application of which results in improvement in some characteristics at the cost of the others

POSSIBILITIES FOR IMPROVING SURFACE DEFECTS OF 3D PRINTED TITANIUM PRODUCTS THROUGH REACTIVE ELECTRO-SPARK PROCESSING

There are two main reasons why researchers are looking for solutions to improve the surface characteristics of products produced by 3D printing (most often by SLM, DMLS technologies):low hardness and the low tribological characteristics of titanium alloys, which limit their application in friction assemblies in many industrial branches; high roughness and defects such as irregularities, micropores, and cracks on the surface of 3D titanium products, which require complex labor-intensive and energy-intensive finishing operations. In the present work, an analysis of literary sources was carried out on ways to improve the surface characteristics and properties of titanium surfaces produced by selective laser melting (SLM). The technological characteristics of the electrospark deposition method as the lightest, most accessible and inexpensive way to improve the surface qualities of 3D products are indicated. The authors\u27 results are presented, where reactive electrospark treatment based on the ESD method has been used based on the ESD method. A simultaneous multidirectional effect is achieved, which is expressed in: up to a fivefold reduction in the roughness of 3D titanium surfaces; filling of the surface pores, cavities and voids; a double increase of microhardness of the modified surfaces; ecological replacement of finishing treatments and economy of labor, equipment, consumables, and energy. Appropriate process and electrical parameters and materials are indicated to realize the above effects

Investigation of the properties of non-tungsten electro-spark coatings on high speed steel

In this work contactless local electro spark deposition (LESD), has been used to received wear resistant coatings from hard alloys based of ТiC, TiN, TiCN onto high speed steel HS6–5–2. The influence of the operating electric parameters and the electrode materials on the roughness, thickness, microhardness, phase composition, and on the structure of resulting coatings was studied. The impact of different electrode materials on the quality characteristics, the composition and structure of the resulting coatings has been found. The technological parameters of the LESD process for the formation of coatings with a predefined roughness, thickness, composition and structure has been determined

POSSIBILITIES FOR IMPROVING THE SURFACE QUALITY OF STRUCTURAL STEELS, INVAR AND TITANIUM ALLOYS THROUGH REACTIVE ELECTROSPARK TREATMENT WITH ELECTRODES OF AN ALUMINUM-SILICON ALLOYS

In the rough and semi-pure processing of metal alloys, as well as in additive technologies, surface defects are often observed - the appearance of scratches, creases, recesses, incisions, pores, ridges, protruding particles, and other unevenness, undesirable spiral or concentric relief, traces of cutting edges of the tool and high roughness on the treated surface. In this work, the possibilities for improving the surface characteristics of materials such as steels, invar and titanium alloys with typical surface defects through reaction electrospark deposition (ESD) are investigated. A study of the conditions for the local formation of reactive phases and reduction of surface roughness during the electrospark modification was performed. Layering electrodes of low-melting Al-Si alloys were used. Their choice was made on the assumption that a liquid melt is formed in the process of ESD. It is expected that it will fill the recesses, pores and scratches and interact with the chemical elements contained in the substrate. The results of the studies of the change in the roughness, thickness and microstructural characteristics of the modified surfaces depending on the energy of the pulses and their influence on the wear resistance at friction are presented. A double effect has been achieved - a significant improvement in both the surface characteristics and the wear resistance of the modified surfaces. It was found that the improvement of surface quality and wear resistance was achieved as a result of partially burning the protrusions, filling the depressions with low melting electrode alloy and local synthesis of wear-resistant surface structures and phases obtained by the chemical interaction of the melt with the substrate. The energy parameters of the electric discharges, the process parameters, and the ESD conditions, suitable for the realization of the above phenomena, have been determined and optimized

GEOMETRIC CHARACTERISTICS, COMPOSITION AND STRUCTURE OF COATINGS OF WC-TIB2-B4C- NI-CR-B-SI-C ELECTRODES FORMED ON 3D PRINTING TITANIUM AND STEELS BY CONTACTLESS ELECTROSPARK DEPOSITION

The object of the present work are the surface properties of technical titanium produced by 3D printing - Direct Metal Laser Sintering (DMLS) with subsequent treatment by local electrospark deposition with a rotating electrode (LESD). The layering was performed with electrodes of multicomponent hard alloys based on WC with additives from B4C, TiB2 and Ni-Cr-B-Si-C and of AlSi alloys. The influence of the LESD process parameters on the roughness, thickness, composition and structure of the coatings was studied by profilometric, metallographic, XRD, SEM and EDS methods. High-density coatings with different roughness and thickness have been obtained, which can be changed by changing the LESD modes in the range Ra=1.25÷3.5μm, δ=6÷20μm and microhardness 9÷14.0 GPa. Friction tests have shown that the wear of coated surfaces is up to 4 times lower than uncoated. On the basis of the experimental data, appropriate process parameters and electrodes have been determined, allowing to obtain coatings with purposeful synthesized of new phases and crystal-amorphous structures, and with predetermined thickness and roughness and higher hardness, and wear resistance than those of substrates

ELIMINATION OF IRREGULARITIES AND DEFECTS ON STEEL SURFACES THROUGH ELECTRO SPARK SURFACE MODIFICATION WITH ALUMINUM ALLOYS

The surface roughness of the parts has a significant influence on their performance properties and it is crucial for the friction force and wear of the bodies. Therefore, in practice it is often necessary to perform finishing treatment to reduce the macro, micro and meso- roughnesses - grinding, honing, lapping, polishing and more. In this study are examined the possibilities of reducing the roughness and the traces of the previous machining of steel surfaces by electro-spark deposition (ESD) with low-melting aluminium alloys. The roughness of the steel surfaces obtained after different milling modes after subsequent electrospark coating was investigated. Dense and uniform coatings with different surface microgeometry are obtained, which to a different extent erase the traces of the preceding processing. The examination of tribological characteristics showed a significant increase in the wear resistance of the coated surfaces. The process parameters and materials for ESD at which coated surfaces have simultaneously the lowest roughness and the highest wear resistance have been determined and optimized