Machines. Technologies. Materials.
Vol. 13 (2019), Issue 8

Table of Contents

  • TECHNOLOGIES

    • Effect of Al-Ti-C system master alloy high energy synthesis on efficiency of Ni based superalloy inoculation

      pg(s) 331-334

      The possibility of high energy synthesis of Ti–Al–C system powder grain refiner by using high voltage electric discharges for treatment of powder mixtures of 75 % Ti + 25 % Al and 85 % Ti + 15 % Al composition in kerosene with subsequent briquetting by spark plasma sintering is shown in present work. It is found out that high voltage electric discharge treatment of powders leads to the increase of dispersity as well as to synthesis of new carbon containing phases during chemical interaction between system components and products of working hydrocarbon liquid destruction. The possibility of controlling this process by changing initial composition of powders, specific treatment energy and spatial distribution of plasma formations by changing electrode system type is shown. It is also shown that changing master alloy synthesis parameters allows controlling inoculation efficiency. Thereby it is possible to achieve surface or volumetric inoculation, so selective increasing of plastic or strength properties of Ni-based cast superalloys becomes possible. Introduction of 0.01 % of synthesized grain refiner during the casting of SM88U (СМ88У) superalloy allows decreasing mean grain size from 1…2 mm to 0.2…0.5 mm. Tensile strength of inoculated superalloy at the temperature of 900˚С was 68 MPa while their stress rupture strength increased by 20 % in average. Composition and properties of inoculated alloys comply with standard technical documentation, which allows their usage for the
      production of gas turbines blades.

    • Virtual evaluation of the influence of independent factors on the force deformation when receiving long-length product from low-alloyed chrome bronze by the SPD method «Conform»

      pg(s) 335-337

      Using computer simulat ion in the environment of the DEFORM-3D appl icat ion package, a virtual ful l factorial experiment was conducted on the process of producing long length workpieces from low -al loyed chrome bronze by equal channel angular pressing (ECAP) using the Conform scheme. During the virtual experiment, an assessment was made of the inf luence of independent factors (impel ler rotat ion speed, number of cycles, and temperature of deformat ion treatment) on the response parameter — deformat ion force. As a resul t of the experiment , a regression equat ion was obtained, a variant of solving the opt imizat ion problem wi th determining the numerical values of the accepted independent factors was presented, an d their inf luence on the response parameter was analyzed.

    • Numerical simulations of honing process of thin wall cylinder liners, with constant and with variable thickness of wall of honed parts

      pg(s) 338-344

      Numerical simulations of honing process of thin-wall cylinder liners, with constant and with variable thickness of the wall of honed workpieces can improve and can help to conduct the experimental research of honing process and can improve the honing process. A very valuable research assumption, before performing the numerical analysis of computer simulation of honing process, is the measurement of the real geometry of the honing head using a CNC coordinate measuring machine and measuring of the honed workpiece’s temperature occurring in the honed workpiece during honing process with a thermal infrared camera. Thick-walled workpieces do not create machining and technological performance problems. In a predictable way, it’s possible to plan the machining time remaining to receive the desired diameter of the hole being honed. Deformations of a thin-walled workpiece with varying wall thickness occurring during honing, which were measured after machining, showed that there is no linear correlation of holes deformation received for a different crosssection thicknesses of wall of honed cylinder liners for various oilstone pressure and due to the workpiece temperature increase.

    • Effect of operating and design variables on stripped sour water quality

      pg(s) 345-348

      As technology evolves, the environmental legislations on pollutant concentrations in aqueous effluents tend to tighten and increase. As a result, sour water must be handled and processed properly in order to provide high quality of stripped water with insignificant traces of NH3 and H2S. This must be achieved within the minimum operating costs.
      This work analyses the effect of operating/design variables (such as feed temperature, feed location, number of stages, and steam flow rate) on the stripped water quality in two cases (A refluxed absorber without a reboiler and an absorber with a side compressor). HYSYS V.8 simulation tool was used to accurately simulate the two cases. The feed data was acquired from the factory of POSCO (Pohang Iron and Steel Corporation) in South Korea.
      It was found that the best stripping efficiency in the refluxed absorber was when the feed was fed at the first stage, with maximum feed temperature, number of stages and steam flow rate. For the absorber with compressor, the feed was fed in the first stage and the reflux split and the pressure ratio were changed to monitor their effect on the tower efficiency. Results showed that increasing the reflux split increases the flow rate of NH3 and acid gases in the off gas, while increasing their concentration in treated water (200 ppm) restricting the use of reflux split. It also proved that increasing the pressure ratio carries more energy to the sour water feed heat exchanger. The effect of
      changing the pressure ratio on the compressed gas temperature and the compressor duty was also studied. Results of the treated wastewater streams guarantee that the effluent sour water obeys standard environmental regulations

    • Formation of innovative policy taken into account of the economic mechanism of innovative activities of industrial enterprises

      pg(s) 349-353

      It is established that the activity of industrial enterprises in conditions of instability of the economic situation in the country, political situation, deterioration of the welfare of the population, imperfection of the current legislation, increase of tax pressure, that is external factors of activity, is aimed at strengthening of competitive positions by penetration a new market segment, production of innovative products, reduction of costs, rational use of resources, under the condition of implementation of technological advances.
      It is determined that the level of innovation activity of enterprises is characterized by a gradual deterioration, since scientific and technological achievements are rather slowly used, manufactured products, based on the use of innovative developments, are not in demand on the foreign market, because it is uncompetitive along with the products of leading enterprises. It is substantiated that there are no favorable conditions for rising the innovation activity of industrial enterprises, since most of them are in crisis or unprofitable, not provided with sources of financing for attracting innovative technologies, sharing experience with international organizations. It is proved that the solution of these problems is the implementation of the innovation policy of industrial enterprises, which is possible under the conditions of formation and use
      of economic mechanism of innovation activity (EMIA). Elements of organizational and economic mechanism of innovative activity and innovative development of industrial enterprises are proposed under condition of formation of innovation policy.

    • Study of the opportunities for building and management of flexible small and medium enterprises in Bulgaria

      pg(s) 354-357

      With transition to the 21st century, there are radical changes that influence on every aspect of the business, including how goods and services are produced. With the launch of Internet and high-speed communication, the market has indeed become global and fragmented. Customers require smaller quantities and more personalized products. Traditional production, with its broad approach and static organizational style, can no longer compete in global markets. Customers are now looking for more flexibility, shorter delivery times and more diverse products and services. The flexibility of an enterprise makes it possible not only to adapt to the rapidly changing environment but also to the opportunities it provides. The flexible enterprise is able quickly to reorganize its people, management, technology, equipment and operational philosophy to produce products and services tailored to customer needs or new markets. Flexibility is a strategic solution for survival in today’s market conditions. Small and medium-sized enterprises are doomed to operate flexibly.

  • MATERIALS

    • Modeling of the metal powder pressing process with a porogen

      pg(s) 358-361

      A model for calculating the metal powder pressing process with a porogen is proposed. An approximate method and algorithm have been developed that make it possible to take into account the presence of a porogen in the calculation of the pressing process and reflect all types of bonds at the contact boundaries of metal powder particles. Based on the constructed model, an approximate method and algorithm for calculating the properties of powder filter material (PFM) produced by pressing granular metal powders using a porogen have been developed. The advantage of the proposed mathematical model is the possibility of its development to describe the sintering process, as well as the possibility of its use for calculating the modified elementary cells used by researchers in modeling the structure of PFM with a porogen.

    • The effect of ball milling speed on the penetration of Cr and Zr into Cu for production of Cu1CrZr alloy powder

      pg(s) 362-366

      The copper alloys are preferred for their superior mechanical properties combined with high electrical conductivity for contact material applications. These properties should be a very good combination of high mechanical strength and enough electrical conduction properties as well as high thermal conductivity. To establish the electrical and thermal conductivity, the low resistive materials such as copper and their alloys to be chosen is a must. Copper can be alloyed with Cr and Zr in very low
      amounts down to 1 wt% and 0.15 wt%, respectively. These amounts can be found from phase diagrams of interest. The planetary ball milling was chosen as being a unique technique for powder processing to obtain mechanochemical activation and mixing of powders prior to sintering. The ball milling jar was ZrO2 and ball to powder ratio was varied as 1:1, 5:1, and 10:1. The ball milling rotation was ranged from 400 and 500 rpm for different durations to be investigated. The SEM photos showed the Cr and
      Zr penetration onto Cu powders transformed to flakes of different sizes. The elemental composition maps showed the better and finer distribution of alloying elements at 500 rpm than 400 rpm.

    • Effect of aging on Zamak 3

      pg(s) 367-369

      Zamak 3 is a zinc-aluminum alloy with a composition of 3.7-4.3 %Al, <0.05 % Cu, 0.02-0.06 % Mg, rest is Zn. It is well suited for pressure die casting and it results in sufficient mechanical properties and a good surface finish. Zamak 3 is utilized in applications automotive industry, household appliances, in structural applications of buildings, etc. It was reported in literatüre that the mechanical properties of the zamak alloys deteriorate in time at room temperature. In the present study, this effect was investigated by artificial aging of zamak 3 alloy.
      Zamak 3 samples were produced by cutting and melting of Zamak 3 ingots at 500 oC, and casting into steel molds. Aging experiments were conducted by keeping the Zamak 3 samples in a muffle furnace for 24 h at temperatures of 85 oC, 105 oC and 130 oC. Optical and scanning electron microscopy was employed for investigating the microstructure of the samples. Hardness values of the samples were measured by a Brinell hardness tester. A universal testing machine was used for conduction three point bending tests of the samples. It was found that both hardness and bending strength of Zamak 3 alloy decreased with increasing aging temperature. Hardness and strength values of Zamak 3 were 89 HB10 and 490MPa, respectively. After aging at 130 oC hardness and strength values were found to fall to 75 Brinell 10 and 415 MPa, respectively.

    • Peculiarities of the interaction of a highly carbonized ferrochrome with iron during sintering of 65% Fe-35% FH800 composite

      pg(s) 370-372

      The influence of temperature of sintering on structure formation, phase composition, microhardness of components of powder composite 65 % wt. Fe – 35 % wt. FH800 were investigated. It has been established that the increase in the temperature of sintering from 1050 ºС to 1250 ºС leads to some increase in volumetric shrinkage, density and decrease in porosity of samples of material which was made from coarse-grained source powders of industrial production components. It was found that the sintering of green compacts in the range of 1000-1300 ºС causes significant changes in the chemical and phase composition of the carbide component of the composite, which are described by a series of phase transformations: M7C3 → M3C (1000-1150 ºС) → M7C3 (1200 ºС) → M3C (1250-1300 ºС)

    • Properties of nanodiamonds of industrial detonation synthesis

      pg(s) 373-375

      Detonation synthesis nanodiamonds have been widely used in modern science and technology. Such kind of nanodiamonds can be obtained either from the carbon explosive molecule (DND) or from a mixture of explosives with the addition of graphite or soot (DALAN). Possessing nanoscale and high surface energy, diamonds have a structural and dispersion-strengthening effect being in contact with any materials. In many ways, the applications of nanodiamonds are determined by their dispersion, reactivity, and aggregative state in various environments. The given scientific research investigated the properties of industrial DND and DALAN produced by JSC RPE “SIDAL”, being one of the leading manufacturers in Russia. There were estimated the following properties: crystallites sizes; elemental composition; thermal stability; specific surface area; unit sizes.